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Tetrahedron Letters
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ISSN (Print) 0040-4039 - ISSN (Online) 1359-8562
Published by Elsevier Homepage  [3182 journals]
  • Linear Oligosulfoxides: Synthesis and Solubility Studies
    • Abstract: Publication date: Available online 22 October 2019Source: Tetrahedron LettersAuthor(s): Bhaskar Halami, Dhananjani N.A.M. Eriyagama, Komal Chillar, Zack Nelson, Lucas Prehoda, Yipeng Yin, Bao-Yuan Lu, Brett Otto, Liam Haggerty, Shiyue Fang Synthesis of three linear oligosulfoxides containing up to six sulfoxide groups was achieved by multiple SN2 reactions between an alkanethiol and alkyl tosylate to give a linear oligosulfide followed by oxidation of the oligosulfide with sodium periodate to give an oligosulfoxide. The challenge of complete avoidance of partial oxidation and over oxidation was easily overcome using the sodium periodate oxidation conditions. Although sulfoxide is a highly polar functional group, the oligosulfoxides were found to have limited solubility in many solvents including DMSO and water, which disobeys the “like dissolves like” rule. The surprising solubility pattern of oligosulfoxides was discussed in the context of the drastically different solubility patterns of polyethylene glycol (PEG), poly(butylene oxide), and poly(methylene oxide). According to a dissolution model, solubility properties of linear oligomers including the oligosulfoxides and PEGs may be heavily affected by their conformations and the suitability of their conformations in water for maximizing attractive interactions between them and water. Based on these hypotheses, the limited solubility of the present oligosulfoxides may not imply the low solubility of similar molecules.Graphical abstractGraphical abstract for this article
       
  • Sinuhirtins A and B, two uncommon norhumulene-type terpenoids from the
           South China Sea soft coral Sinularia hirta
    • Abstract: Publication date: Available online 22 October 2019Source: Tetrahedron LettersAuthor(s): Si-Qi Lu, Xu-Wen Li, Song-Wei Li, Zan Cui, Yue-Wei Guo, Guan-Ying Han Two new uncommon norhumulene-type norsesquiterpenoids, namely sinuhirtins A (1) and B (2), along with two known norcaryophyllene-type norsesquiterpenoids (3 and 4), were isolated from the South China Sea soft coral Sinularia hirta. The structure and absolute configuration of the new compounds were determined by extensive spectroscopic data analyses, and computer-assisted methods including GIAO 13C NMR and TDDFT-ECD calculations. A plausible biogenetic relationship of 1-4 was proposed.Graphical abstractGraphical abstract for this article
       
  • Euphatexols A and B, two unusual euphane triterpenoids from the latex of
           Euphorbia resinifera
    • Abstract: Publication date: Available online 21 October 2019Source: Tetrahedron LettersAuthor(s): Yanru Qi, Wei Liu, Yu Chen, Ming Guan, Tao Yuan Two unusual euphane triterpenoids, named euphatexols A (1) and B (2), were isolated from the latex of Euphorbia resinifera. Their structures were elucidated based on the extensive analysis of spectroscopic data (HRMS, 1D and 2D NMR). Compound 1 possesses a rare tetrahydrofuran ring formed via C-1 and C-11, which is firstly reported in euphane triterpenoids. Compound 2 represents an unusual 27-nor-euphane triterpenoid. Moreover, compounds 1 and 2 showed significant cytotoxic activities against HepG2 cells with 87.0% and 87.4% inhibition rate at 1 μM, respectively.Graphical abstractGraphical abstract for this article
       
  • Base Induced Cyclobutenone Rearrangements and Its Application in the
           Synthesis of Aromatic Amines
    • Abstract: Publication date: Available online 19 October 2019Source: Tetrahedron LettersAuthor(s): Xiaodan Han, Jianping Fu, Juwu Hu, Wei Xiong, Huibin Wang, Lei Wu A series of fully substituted 2-pyridone 2 and functionalized α-pyrones 3 are synthesized starting from cyclobutenones 1 under a base-promoter in toluene at 80 ℃. This rearrangement is complimentary to the previously reported ring expansion of cyclobutenones, providing a divergent synthesis of corresponding products from the same precursor 1. In addition, α-pyrones 3 has also been applied to the synthesis of aromatic amines 7 in good yields (64–83%) and in a highly regioselective manner via D-A reaction under mild conditions.Graphical abstractGraphical abstract for this article
       
  • One-pot synthesis of benzofluorene fused aromatic hydrocarbons
    • Abstract: Publication date: Available online 19 October 2019Source: Tetrahedron LettersAuthor(s): Wendan Dong, Zhun Hu, Ziqi Wang, Bing Sun, Xueqiong Zhang, Fang-Lin Zhang A new and efficient synthetic approach for the one-pot construction of benzofluorene fused aromatic hydrocarbons was developed via a transient-directing group strategy. The palladium-catalyzed cascade reaction proceeded via consecutive arylation, cyclization and aromatization steps. Moderate to good yields along with broad functional group tolerance were achieved under mild reaction conditions.Graphical abstractGraphical abstract for this article
       
  • Colorimetric detection of spermine and spermidine by zincon in aqueous
           solution
    • Abstract: Publication date: Available online 18 October 2019Source: Tetrahedron LettersAuthor(s): Yasumasa Fukushima, Shunichi Aikawa The anionic organic dye, zincon, was found to be a colorimetric probe for spermine and spermidine at pH 4.0 in pure aqueous solution through its aggregation by electrostatic interactions with them. The addition of spermine and spermidine led to bathochromic shifts with color changes from yellow to purple and dark brown, respectively, while other amines and basic amino acids induced no or minimal spectral and color changes. From Job’s plot and titration experiments, zincon interacted with spermine (+4 charges) and spermidine (+3 charges) in 4:1 and 3:1 stoichiometric ratios, respectively, indicating that each positive charge was bound to one zincon molecule. The detection limits were determined to be 25.1 for spermine and 30.7 nM for spermidine, which were sufficient below the critical concentration for cancer diagnosis. The results indicated that zincon can be a good candidate for simple, convenient colorimetric detection of spermine and spermidine in aqueous solution.Graphical abstractTo create your abstract, type over the instructions in the template box below. Fonts or abstract dimensions should not be changed or altered.Graphical abstract for this article
       
  • A one-pot and three-component synthetic approach for the preparation of
           asymmetric and multi-substituted 1,4-dihydropyrazines
    • Abstract: Publication date: Available online 18 October 2019Source: Tetrahedron LettersAuthor(s): Fariba Peytam, Mehdi Adib, Reihaneh Shourgeshty, Mahmoud Rahmanian-Jazi, Mehdi Jahani, Bagher Larijani, Mohammad Mahdavi An efficient, one-pot and three-component synthesis of a new series of 2-acyl-3,4,6-triaryl-1,4-dihydropyrazines is described. This two-step strategy involves treatment of phenacyl bromides and anilines to give the nucleophilic substitution intermediate followed by Michael-addition-cyclization to α-azidochalcones to afford the title compounds in high yields.Graphical abstractGraphical abstract for this article
       
  • Helical foldamer-catalyzed enantioselective 1,4-addition reaction of
           dialkyl malonates to cyclic enones
    • Abstract: Publication date: Available online 18 October 2019Source: Tetrahedron LettersAuthor(s): Tomohiro Umeno, Atsushi Ueda, Mitsunobu Doi, Takuma Kato, Makoto Oba, Masakazu Tanaka The introduction of a five-membered ring α,α-disubstituted α -amino acid into L-Leu-based heptapeptides preferentially induced right-handed (P) helical structures. Using 5∼20 mol % of a single helical foldamers-catalyst, enantioselective 1,4-addition reactions of dialkyl malonates to cycloalk-2-enones (5∼7 rings) proceeded to give chiral 3-substituted cycloalkanones with 94∼99% ee in moderate chemical yields, regardless of the ring size of substrates.Graphical abstractGraphical abstract for this article
       
  • Copper(II)-catalyzed Preparation of Alkylindium Compounds and Applications
           in Cross-Coupling Reactions Both in Aqueous Media
    • Abstract: Publication date: Available online 18 October 2019Source: Tetrahedron LettersAuthor(s): Peng Wang, Bing-Zhi Chen, Yi-Cong Guo, Weidong Rao, Zhi-Liang Shen An efficient water-based method for the synthesis of alkylindium compound in the presence of a catalytic amount of cheap and readily available CuSO4·5H2O (10 mol%) was developed. The thus-generated alkylindium compounds effectively underwent palladium-catalyzed cross-coupling reactions with a myriad of aryl halides in aqueous media, leading to the cross-coupled products in modest to high yields. The mildness of the formed alkyl organometallics allowed the tolerance to various important functional groups incorporated in both substrates of alkyl iodides and aryl halides.Graphical abstractGraphical abstract for this article
       
  • Novel secoeunicellins produced by an octocoral Cladiella sp.
    • Abstract: Publication date: Available online 18 October 2019Source: Tetrahedron LettersAuthor(s): Zhi-Jun Zhang, Yi-Hsuan Wang, Shu-Rong Chen, Bo-Rong Peng, San-Nan Yang, Chiung-Chih Hu, Lee-Shing Fang, Tsong-Long Hwang, Ping-Jyun Sung Two novel 6,7-secoeunicellins, cladieunicellins W (1) and X (2), along with a known eunicellin, klymollin Y (3), were isolated from an octocoral identified as Cladiella sp. The structures of secoeunicellins 1 and 2 were elucidated by spectroscopic methods. 1 is the first secoeunicellin possessing a γ-lactone ring and 2 represents the first secoeunicellin possessing two tetrahydrofuran moieties. Secoeunicellin 2 displayed significant inhibitory effects on the generation of superoxide anions and the release of elastase. These results implied that the methoxy group at C-6 in 2 plays an important role in determining the activity of these compounds.Graphical abstractGraphical abstract for this article
       
  • An alternatively metal-free synthesis of 1,3,5-triazines or
           1,2,4-thiadiazoles from benzyl chlorides and benzylamines mediated by
           elemental sulfur
    • Abstract: Publication date: Available online 17 October 2019Source: Tetrahedron LettersAuthor(s): Yurong Zhang, Yafei Liu, Jun Zhang, Ren Gu, Shiqing Han An elemental sulfur mediated reaction of benzyl chlorides with benzylamines is developed, which allows the practical synthesis of valuable 1,3,5-triazines. This protocol that is metal free, ligand free, and uses inexpensive elemental sulfur as oxidant or raw material displays mild reaction conditions, a broad substrate scope and moderate to good yields. Moreover, the modified sulfur-mediated reaction system can also be used to synthesize 1,2,4-thiadiazoles, by simply switching the stoichiometry of sulfur powder from 0.75 equivalents to 5 equivalnts.Graphical abstractGraphical abstract for this article
       
  • AlCl3-promoted three-component cascade reaction for rapid access to
           [1,2,3]triazolo[5,1-a]isoquinolines
    • Abstract: Publication date: Available online 17 October 2019Source: Tetrahedron LettersAuthor(s): Yangang Wu, Yonggang Meng, Zibo Liu, Mengge Zhang, Chuanjun Song Novel AlCl3-promoted, three component cascade Henry reaction-triazole formation-intramolecular 6-endo-dig cyclization reactions between 2-alkynylaryl aldehydes, nitroalkanes, and sodium azide for the assembly of [1,2,3]triazolo[5,1-a]isoquinolines have been developed. Further transformations of representative [1,2,3]triazolo[5,1-a]isoquinolines are also described.Graphical abstractGraphical abstract for this article
       
  • First Cp*Co(III)-Catalyzed Mizoroki-Heck Coupling Reactions of Alkenes and
           Aryl bromide/Iodide
    • Abstract: Publication date: Available online 16 October 2019Source: Tetrahedron LettersAuthor(s): Avinash K. Srivastava, Naveen Satrawala, Munsaf Ali, Charu Sharma, Raj K. Joshi A Cp*Co(CO)I2 catalyzed Mizoroki-Heck coupling of alkenes and aryl halide is established at feasible reaction conditions. The Cp*Co(III) catalyst excellently work to couple the aryl iodide and alkene, and produce up to 94% yield of the coupling product. In case of the coupling of aryl bromide and alkene, slightly reduced activity of the catalyst was observed, and moderate to good yield of the product was obtained. Apart from functionally different styrene, the catalyst was also able to activate the acrylates, which seems difficult to be activated by other reported metal complexes. The coupling proposed herein is tolerant a wide variety of aryl halides, stryenes, and acrylates enable to form C-C bond using inexpensive metal in catalysis. Hence, the present catalyst is highly economical, consists a non-endangered metal and is highly efficient for Heck coupling reaction. Moreover, the cobalt metal in high oxidation state (+3) is not much explored for the C-C cross-coupling reactions.Graphical abstractGraphical abstract for this article
       
  • Efficient synthesis of sulfonylguanidines via reaction of
           tetra-substituted urine with ArSO2NCO
    • Abstract: Publication date: Available online 16 October 2019Source: Tetrahedron LettersAuthor(s): Jianjie Han, Rongyan Zhou, Chao Huang, Qingkai Zeng, Qiumeng Long, Qianjun Zhang, Hang Cong, Qingdi Zhou, Gang Wei, Mao Liu An efficient synthesis of sulfonylguanidines via reaction of tetra-substituted urines with ArSO2NCO has been developed with good yields, which provides a convenient way for synthesis of sulfonyl group protected guanidine from urine in one step.Graphical abstractGraphical abstract for this article
       
  • Synthesis of aromatic substituted B←N embedded units with good stability
           and strong electron-affinity
    • Abstract: Publication date: Available online 16 October 2019Source: Tetrahedron LettersAuthor(s): Yuqing Li, Bo Pang, Huifeng Meng, Ying Xiang, Yongchun Li, Jianhua Huang Two chemically stable B←N embedded units were synthesized, namely, BNIDT-Ph and BNIDT-Th, with aromatic phenyl (Ph) or thiophene (Th) groups, respectively, attached to the four coordination boron (B) atom. Single crystal data revealed that BNIDT-Ph and BNIDT-Th show obvious π-π interactions (3.83 vs. 3.79 Å) and B←N dipole-dipole interactions (6.51 vs. 6.67 Å). BNIDT-Ph and BNIDT-Th exhibit strong electronic affinities of 3.70 and 3.81 eV, respectively. Fluorescence quenching was found between PBDB-T and the B←N embedded molecules in solution, indicating exciton dissociation. These B←N embedded molecules are potentially useful to further construct novel n-type semiconductors.Graphical abstractGraphical abstract for this article
       
  • Graphical abstract TOC
    • Abstract: Publication date: 31 October 2019Source: Tetrahedron Letters, Volume 60, Issue 44Author(s):
       
  • Graphical abstract TOC
    • Abstract: Publication date: 31 October 2019Source: Tetrahedron Letters, Volume 60, Issue 44Author(s):
       
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    • Abstract: Publication date: 31 October 2019Source: Tetrahedron Letters, Volume 60, Issue 44Author(s):
       
  • Direct lactonization from 1,3-dienes and malonate esters mediated by a
           combination of iodine and visible light
    • Abstract: Publication date: Available online 16 October 2019Source: Tetrahedron LettersAuthor(s): Mitsumi Takeda, Saki Maejima, Eiji Yamaguchi, Akichika Itoh This manuscript describes the reaction of dienes with carbonyls in the presence of molecular iodine under visible light irradiation to furnish the corresponding butyrolactones with complete site selectivity. The reaction proceeds via site selective sequential addition of iodine radical, which is generated from molecular iodine under visible light irradiation, to dienes to form a reactive intermediate, followed by substitution and cyclization. A variety of dienes and carbonyls are well tolerated under the reaction conditions. This transformation constitutes the first iodine radical-mediated intermolecular lactonization reaction of dienes.Graphical abstractGraphical abstract for this article
       
  • New approaches to the synthesis of benzo[h]pyrroloisoquinoline
           derivatives
    • Abstract: Publication date: Available online 15 October 2019Source: Tetrahedron LettersAuthor(s): Anastasia A. Ershova, Anna D. Zinoveva, Tatiana N. Borisova, Alexander A. Titov, Alexey V. Varlamov, Leonid G. Voskressensky, Van Tuyen Nguyen, Tuan Anh Le An effective strategy for the synthesis of benzo[h]pyrrolo[2,1-a]isoquinoline derivatives has been developed. The process can be described as a one-pot domino reaction that consists of an initial Michael addition, intramolecular cyclization, and subsequent transformations leading to the formation of the desired products. A wide range of structurally diverse hydrogenated benzo[h]pyrrolo[2,1-a]isoquinolines were obtained in 34-98% yield. This strategy represents an efficient catalyst-free procedure that allows the synthesis of previously inaccessible compounds.Graphical abstractTo create your abstract, type over the instructions in the template box below. Fonts or abstract dimensions should not be changed or altered.Graphical abstract for this article
       
  • Hantzsch-like three-component synthesis of tetracyclic 10b-azachrysenes:
           unambiguous structural elucidation using X-ray crystallography and 2D-HMBC
           spectroscopy
    • Abstract: Publication date: Available online 15 October 2019Source: Tetrahedron LettersAuthor(s): Fatma M. Saleh, Hamdi M. Hassaneen, Holger Butenschön, Gerald Dräger, Ismail A. Abdelhamid Herein, we report the first synthesis of 10b-azachrysenes via the Hantzsch-like reaction of aldehydes with 2-(6,7-dimethoxy-3,4-dihydroisoquinolin-1-yl)acetonitrile and dimedone in the presence of acetic acid. The regioselectivity was established using X-ray crystallography and 2D-HMBC spectroscopy.Graphical abstractGraphical abstract for this article
       
  • Synthesis of Chiral Quaternary Fluorinated Cyclic Sulfamidates via
           Palladium-catalyzed Arylation with Arylboronic Acids
    • Abstract: Publication date: Available online 15 October 2019Source: Tetrahedron LettersAuthor(s): Mu-Wang Chen, Xuechun Mao, Yue Ji, Jianjun Yuan, Zhihong Deng, Yiyuan Peng An enantioselective palladium-catalyzed arylation of fluorinated cyclic N-sulfonyl ketimines with arylboronic acids is described. This methodology provides an efficient and convenient route to chiral quaternary fluorinated cyclic sulfamidates in high yields with up to 99% ee.Graphical abstractGraphical abstract for this article
       
  • Synthesis of novel 1,2,3-triazolyl nucleoside analogues bearing uracil,
           6-methyluracil, 3,6-dimethyluracil, thymine, and quinazoline-2,4-dione
           moieties
    • Abstract: Publication date: Available online 15 October 2019Source: Tetrahedron LettersAuthor(s): Olga V. Andreeva, Maya G. Belenok, Liliya F. Saifina, Marina M. Shulaeva, Alexey B. Dobrynin, Radmila R. Sharipova, Alexandra D. Voloshina, Alina F. Saifina, Aidar T. Gubaidullin, Bulat I. Khairutdinov, Yuriy F. Zuev, Vyacheslav E. Semenov, Vladimir E. Kataev A series of novel 1,2,3-triazolyl nucleoside analogues was synthesized via the CuAAC reaction of N1-alkynyl uracil, 6-methyluracil, 3,6-dimethyl uracil, thymine and quinazolin-2,4-dione with protected azido β-D-ribofuranose. The obtained compounds differ in both the nature of the pyrimidine-2,4-dione fragment and the length of the polymethylene linker connecting it with the β-D-ribofuranosyl-1,2,3-triazol-4-yl moiety. The 1,2,3-triazolyl nucleoside analogues were evaluated for their cytotoxicity in vitro.Graphical abstractGraphical abstract for this article
       
  • H+bromination+of+benzaldehydes+via+a+monodentate+transient+directing+group+strategy&rft.title=Tetrahedron+Letters&rft.issn=0040-4039&rft.date=&rft.volume=">Palladium-catalyzed ortho-C(sp2)H bromination of benzaldehydes via a
           monodentate transient directing group strategy
    • Abstract: Publication date: Available online 14 October 2019Source: Tetrahedron LettersAuthor(s): Qiyun Yong, Bing Sun, Fang-Lin Zhang A facile and efficient monodentate transient directing group strategy was developed to enable the palladium-catalyzed ortho-C(sp2)H bromination of benzaldehydes. A broad scope of benzaldehydes were transformed into the desired products by employing 2-amino-5-chlorobenzotrifluoride as a monodentate transient directing group, demonstrating good functional group tolerance. Mild reaction conditions and no requirement for a silver salt are also features of this strategy.Graphical abstractGraphical abstract for this article
       
  • An Unexpected Pummerer Rearrangement in the Synthetic Route to Ethyl
           (2'-hydroxy-4',5'-methylenedioxyphenyl)acetate: An Alternative Approach to
           2,3-Dimethylthio Benzofurans
    • Abstract: Publication date: Available online 14 October 2019Source: Tetrahedron LettersAuthor(s): Ariel Carreño-Montero, Luis A. Maldonado, María Isabel Chávez, Simón Hernández-Ortega, Guillermo Delgado The synthesis of ethyl (2'-hydroxy-4',5'-methylendioxophenyl)acetate, a fragment of the antihyperglycemic natural coumarin subcoriacin, is reported. We found an expeditious route to the title compound in five steps. Final metal catalyzed acid ethanolysis of the vinylic 1,1-methylthio methylsulfoxide derivative afforded the required aryl acetic ester, but in the absence of metal catalyst, an unexpected Pummerer rearrangement produced the 2,3-dimethylthiofuran derivative as the major product. This last result provides an alternative entry to 2,3-dimethlythiobenzofurans.Graphical abstractGraphical abstract for this article
       
  • First asymmetric enantioselective total synthesis of phenanthridine
           alkaloid, (S)-(+)-asiaticumine and its enantiomer
    • Abstract: Publication date: Available online 14 October 2019Source: Tetrahedron LettersAuthor(s): Takashi Nishiyama, Shuuya Takaiwa, Rika Kotouge, Satomi Tani, Rikako Yoshinaga, Erina Hamada, Mai Endo, Yuka Sugino, Noriyuki Hatae, Satoshi Hibino, Tominari Choshi In this study, the first asymmetric enantioselective total syntheses of (+)-asiaticumine A (2) and its enantiomer were accomplished through a seven-step sequence using the bond formation between the C4a and N5 positions of the phenanthridine framework based on the microwave-assisted electrocyclization of cyclohexenylbenzaldoxime methyl ether as an aza 6π-hexatriene system followed by the Sharpless asymmetric dihydroxylation as the key step. In addition, the absolute configuration of natural (+)-2 was determined to be S by Mosher’s method.Graphical abstractGraphical abstract for this article
       
  • Reinvestigation of the synthesis of “covalent-assembly” type probes
           for fluoride ion detection. Identification of novel
           7-(diethylamino)coumarins with aggregation-induced emission properties
    • Abstract: Publication date: Available online 14 October 2019Source: Tetrahedron LettersAuthor(s): Valentin Quesneau, Benoît Roubinet, Pierre-Yves Renard, Anthony Romieu An unprecedented C-3 functionalization of 4-(diethylamino)salicylaldehyde through a Friedel-Crafts type alkylation reaction has been discovered during the synthesis of “covalent-assembly”-based fluorescent probes for detection of fluoride ions. The resulting Friedel-Crafts adduct was successfully used for the preparation of two novel 8-substituted 7-(diethylamino)coumarin dyes. The photophysical study of these fluorophores has enabled us to highlight their remarkable aggregation-induced emission (AIE) properties characterized by a yellow-orange emission of aggregates in water. Therefore, 4-(tert-butyldimethylsilyloxy)benzyl substituent was identified as a novel AIE-active moiety which could be seen as a possible alternative to popular tetraphenylethylene (TPE).Graphical abstractGraphical abstract for this article
       
  • Photoredox catalytic cascade radical addition/aromatization of
           methylene-2-oxazolines: mild access to C(sp3 )-difluoro-oxazole
           derivatives
    • Abstract: Publication date: Available online 14 October 2019Source: Tetrahedron LettersAuthor(s): Gui-Ting Song, Chuan-Hua Qu, Jiang-Ping Meng, Zhi-Gang Xu, Cheng-He Zhou, Zhong-Zhu Chen Oxazoles are pivotal structural scaffolds in coordination chemistry, natural products, medicinal chemistry, and material science.[1] Consequently, the synthesis of functionalized oxazoles with multiple pharmacological and biological properties has become the subject of intense research in recent decades.[2] The difluoromethylene group (CF2), which is a bioisostere for an oxygen atom, can significantly affect the acidity, dipole moments, and conformational changes of neighbouring groups.[3] Taken together, the combination of a difluoromethylene group and an oxazole unit in a difluoroalkylated oxazole skeleton could enrich the diversity of oxazoles with new bioactivities.Graphical abstractGraphical abstract for this article
       
  • First Total Synthesis of Versicotide D and Anologs
    • Abstract: Publication date: Available online 14 October 2019Source: Tetrahedron LettersAuthor(s): Laura Posada, Gloria Serra The first total synthesis of cyclotetrapeptide versicotide D has been achieved in 21% overall yield using solid phase peptide synthesis and solution cyclization. In addition, in the search for candidates of antimalarial new drugs, one cyclic tetrapeptide analog which differs in the sequence, and four cyclic pentapeptide containing N-methyl amino acids, were prepared. The obtained compunds were evaluated against P. falciparum 3D7. Versicotide D showed low micromolar antiplasmodial activity.Graphical abstractGraphical abstract for this article
       
  • Enzyme-mediated oxidative dimerization reactions of cyano-resveratrol
           analogues
    • Abstract: Publication date: Available online 14 October 2019Source: Tetrahedron LettersAuthor(s): Zhibo Shao, Xiaodong Kang, Hongpeng Li, Lu Ran, Wenling Li The synthesis and oxidative coupling reactions of two cyano-resveratrol analogues were studied. An 8-5-coupled dihydrobenzofuran-type dimer and an 8-8-coupled diastereoisomeric indane mixture were prepared. The cyano groups of the resveratrol analogues had almost no influence on the regio- or stereoselectivity of the coupling reactions of the two precursors.Graphical abstractGraphical abstract for this article
       
  • Ni/NHC-Catalyzed Cross-Coupling of Methyl Sulfinates and Amines for Direct
           Access to Sulfinamides
    • Abstract: Publication date: Available online 12 October 2019Source: Tetrahedron LettersAuthor(s): Gang-Jian Li, You-Lu Pan, Yan-Ling Liu, Hai-Feng Xu, Jian-Zhong Chen It was reported to develop a simple and convenient method for the Ni/NHC-catalyzed cross-coupling of methyl sulfinates and amines without an acid/base to afford secondary or tertiary sulfinamides in moderate to good yields. The method can provide the desired products with broad substrate scope, good chemoselectivity and good functional group compatibility. The presented approach may enrich the Ni/NHC catalyst system and promote the applications of methyl sulfinates in the organic sulfur chemistry.Graphical abstractGraphical abstract for this article
       
  • Corrigendum to “Electrophilic chemistry of dodecahedran. Direct entry to
           epoxydodecahedrane and the first tethered derivative” [Tetrahedron Lett.
           32/39 (1991) 5259–5262]
    • Abstract: Publication date: Available online 12 October 2019Source: Tetrahedron LettersAuthor(s): Leo A. Paquette, Dean R. Lagerwall, John L. King, Satomi Niwayama, Renato Skerlj
       
  • Simple and Rapid p-Methoxybenzylation of Hydroxy and Amide Groups at Room
           Temperature by NaOt-Bu and DMSO
    • Abstract: Publication date: Available online 12 October 2019Source: Tetrahedron LettersAuthor(s): Shohei Hamada, Koichi Sugimoto, Masashi Iida, Takumi Furuta The p-methoxybenzylation of hydroxy and amide groups by p-methoxybenzyl chloride utilizing NaOt-Bu in DMSO is described. p-Methoxybenzylation of sterically hindered menthol using NaOt-Bu in DMSO proceeded faster than the commonly used methods which use NaH in THF or DMF for p-methoxybenzylation of hydroxy and amide groups. The described method was applicable for sterically hindered substrates at room temperature without adding any activating reagents such as tetrabutylammonium iodide.Graphical abstractGraphical abstract for this article
       
  • Graphical abstract TOC
    • Abstract: Publication date: 24 October 2019Source: Tetrahedron Letters, Volume 60, Issue 43Author(s):
       
  • Graphical Abstract TOC
    • Abstract: Publication date: 24 October 2019Source: Tetrahedron Letters, Volume 60, Issue 43Author(s):
       
  • Graphical abstract TOC
    • Abstract: Publication date: 24 October 2019Source: Tetrahedron Letters, Volume 60, Issue 43Author(s):
       
  • One-Pot Enol Silane Formation-Mukaiyama Aldol Reactions: Crossed
           Aldehyde-Aldehyde Coupling, Thioester Substrates, and Reactions in Ester
           Solvents
    • Abstract: Publication date: Available online 28 September 2019Source: Tetrahedron LettersAuthor(s): C. Wade Downey, Grant J. Dixon, Jared A. Ingersoll, Claire N. Fuller, Kenneth W. MacCormac, Anna Takashima, Rohina Sediqui Trimethylsilyl trifluoromethanesulfonate (TMSOTf) and a trialkylamine base promote both in situ enol silane/silyl ketene acetal formation and Mukaiyama aldol addition reactions between a variety of reaction partners in a single reaction flask. Isolation of the required enol silane or silyl ketene acetal is not necessary. For example, crossed aldol reactions between α-disubstituted aldehydes and non-enolizable aldehydes yield β-hydroxy aldehydes in good yield. In a related reaction, the common laboratory solvent ethyl acetate functions as both an enolate precursor and a green reaction solvent. When thioesters are employed as enolate precursors, high yields for additions to non-enolizable aldehydes are routinely observed.Graphical abstractGraphical abstract for this article
       
  • A chloroacetate based ratiometric fluorescent probe for cysteine detection
           in biosystems
    • Abstract: Publication date: Available online 27 September 2019Source: Tetrahedron LettersAuthor(s): Zhengkun Liu, Qianqian Wang, Hao Wang, WenTing Su, Shouliang Dong The specific detection of cysteine (Cys) over homocysteine (Hcy), glutathione (GSH) and other amino acids is of great significance for studying its biological functions as well as for the diagnosis of related diseases. Chloracetyl group was often used as reaction site for cysteine fluorescent probes for its sensitivity and selectivity. However, high background fluorescence and low stability are common problems encountered by such probes. Here, four chloracetyl group based fluorescent probes (C1, C2, C3 and H4) was synthesized for a comparative study. We found that the inefficient quenching ability of chloracetyl group turned into an advantage when connected with ratiometric fluorophore. With the modification of chloracetyl group, probe H4 displayed great ratiometric property and great selectivity for Cys, the stability was also improved. Additionally, the probe was successfully applied for detecting and real time imaging of Cys in fatal bovine serum and living HeLa cells with low toxicity.Graphical abstractGraphical abstract for this article
       
  • Synthesis of homo-Propargylic ethers: A Domino Ring Opening/Coupling
           Reaction of Oxiranes with Terminal Alkynes and Aryl iodides
    • Abstract: Publication date: Available online 27 September 2019Source: Tetrahedron LettersAuthor(s): Milad Jahanshad, Mohammadreza Manafi, Seyed Mahmoud Mousavi-Safavi, Seyed Saied Homami, Majid Ghazanfarpour-Darjani A domino ring opening/cross-coupling reaction of oxiranes with terminal alkynes and aryl iodides has been developed. This transformation serves as a protocol for the synthesis of homo-alkyne ether skeletons from the readily available starting materials. The success of the reaction has dependence on catalyst/ligand system of choice. The synthesis utility of the alkyne ether skeletons in formation of chromane skeleton has also been studied.Graphical abstractGraphical abstract for this article
       
  • New synthetic route to 2,2,6,6-tetraethylpiperidin-4-one: a
           key-intermediate towards tetraethyl nitroxides
    • Abstract: Publication date: Available online 26 September 2019Source: Tetrahedron LettersAuthor(s): Nikola Babić, Fabienne Peyrot A new synthetic route to 2,2,6,6-tetraethylpiperidin-4-one and derived aminoxyl (nitroxide) radicals is described. In this preliminary work, 2,2,6,6-tetraethylpiperidin-4-one was obtained from ethyl acetoacetate in 3% yield over eight steps, relying only on common reagents and laboratory equipment for organic synthesis.Graphical abstractGraphical abstract for this article
       
  • Photoaddition Reactions of Azomethine Ylides Generated from
           α-Aminonitriles to Fullerene C60: Formation of Fulleropyrrolidines and
           Reaction Efficiencies Changes Depending on Reaction Conditions
    • Abstract: Publication date: Available online 26 September 2019Source: Tetrahedron LettersAuthor(s): Suk Hyun Lim, Dae Won Cho Photoaddition reactions of C60 with both (trimethylsilyl)methyl and either benzyl or phenethyl group containing α -aminonitriles were carried out to explore how product distributions and reaction efficiencies can be influenced by reaction solvent systems. The results show that photoreactions produce both trimethylsilyl- and cyano group containing fulleropyrrolidines as a major (or exclusive) product. Especially, photoreactions performed in either EtOH containing solution or oxygenated environment take place with a much more efficient manner.Graphical abstractGraphical abstract for this article
       
  • Divergent Synthesis of Spiro-cyclopentene-pyrazolones and Pyrano[2,3-c]-
           pyrazoles via Lewis Base Controlled Annulation Reactions
    • Abstract: Publication date: Available online 24 September 2019Source: Tetrahedron LettersAuthor(s): Wenjun Luo, Bingxuan Shao, Jingyi Li, Dingguo Song, Xiao Yi, Fei Ling, Weihui Zhong An effective Lewis base catalyst-controlled α-regioselective annulation reaction of γ-substituted allenoates with unsaturated pyrazolones has been developed, affording various spiro-cyclopentene-pyrazolones and pyrano[2,3-c]pyrazoles. The combination of PPh3 and K2CO3 promoted the [3+2] annulation to access the spiro-cyclopentene-pyrazolones in moderate to good yields (up to 90%) with excellent diastereoselectivities (dr>19:1), while [4+2] annulations to generate pyrano[2,3-c]pyrazoles were successfully achieved by employing DBU as catalyst (in up to 92% yield). Of importance, the asymmetric synthesis of spiro-cyclopentene-pyrazolone was realized by using our previously reported chiral ferrocenylphosphine catalyst.Graphical abstractGraphical abstract for this article
       
  • Features of Oxa-Bridge Cleavage in
           Hexahydro-3a,6-Epoxyisoindol-1(4H)-ones: a Concise Method to Access
           Acetylisoindolones Possessing Anti-viral Activity
    • Abstract: Publication date: Available online 24 September 2019Source: Tetrahedron LettersAuthor(s): Vladimir P. Zaytsev, Dmitriy F. Mertsalov, Lala V. Chervyakova, Gaddam Krishna, Fedor I. Zubkov, Pavel V. Dorovatovskii, Victor N. Khrustalev, Vladimir V. Zarubaev Unusual stereo- and regioselective methods for epoxy-bridge cleavage in perhydro-3a,6-epoxyisoindolones, under the action of the BF3•Et2O/Ac2O system, were discovered. The reaction pathway strongly depends on the characteristics of the isoindolone ring substituents and allows the synthesis of a wide diversity of isoindole-containing heterocycles. The obtained isoindolinones belong to a new class of anti-viral agents possessing a high activity against influenza virus A/Puerto Rico/8/34 (H1N1) in in vitro experiments.Graphical abstractStereo- and regioselective methods for epoxy-bridge cleavage in perhydro-3a,6-epoxyisoindolones were discovered.The reaction pathway developed is very simple and strongly depends on the characteristics of substituents.Hexahydroisoindoles display antiviral activity against the influenza virus H1N1.Graphical abstract for this article
       
  • One-pot carbonyl reduction and carbonate formation using sodium
           borohydride in dialkyl carbonate solvents
    • Abstract: Publication date: Available online 24 September 2019Source: Tetrahedron LettersAuthor(s): Abdulakeem Osumah, Jakob Magolan, Kristopher V. Waynant Preparation of mixed carbonates proceeded in one step from ketones and aldehydes via treatment with NaBH4 in dimethyl or diethyl carbonate solvent at elevated temperatures. This is an efficient and convenient alternative to the traditional two-step sequence of carbonyl reduction to alcohol and subsequent carbonate formation by treatment with an alkyl chloroformate. 25 examples are presented from 49-92% yield, highlighting the versatility of this reaction.Graphical abstractGraphical abstract for this article
       
  • Facile synthesis of 2-carboxanilido-3-arylquinazolin-4-ones from
           N 1-(2-carboxyphenyl)-N 2-(aryl)oxalamides
    • Abstract: Publication date: Available online 24 September 2019Source: Tetrahedron LettersAuthor(s): Vakhid A. Mamedov, Vera L. Mamedova, Alexandra D. Voloshina, Temur A. Kushatov, Victor V. Syakaev, Shamil K. Latypov, Aidar T. Gubaidullin, Dmitry E. Korshin, Daina N. Buzyurova, Il'dar Kh. Rizvanov, Oleg G. Synyashin A simple and efficient approach for the synthesis of novel 2-carboxanilido-3-arylquinazolin-4-ones via the one-pot condensation of readily available N1-(2-carboxyphenyl)-N2-(aryl)oxalamides with various aromatic amines is described. Notably, this methodology allows us to synthesize 3-aryl-quinazolin-4-ones using aromatic amines with various substituents, both electron-donating and electron-withdrawing, which ensures structural diversity of the products and an atomic-economic process.Graphical abstractGraphical abstract for this article
       
  • Cross-Linked Poly(4-Vinylpyridine-N-Oxide) as a Polymer-Supported Oxygen
           Atom Transfer Reagent
    • Abstract: Publication date: Available online 23 September 2019Source: Tetrahedron LettersAuthor(s): Anna M. Bauer, Erin E. Ramey, Kjersti G. Oberle, Gretchen A. Fata, Chloe D. Hutchison, Christopher R. Turlington Oxygen atom transfer (OAT) reagents are common in biological and industrial oxidation reactions. While many heterogeneous catalysts have been utilized in OAT reactions, heterogeneous OAT reagents have not been explored. Here, cross-linked poly(4-vinylpyridine-N-oxide), called x-PVP-N-oxide, was tested as a heterogeneous OAT reagent and its oxidation chemistry compared to its molecular counterpart, pyridine-N-oxide. The insoluble oxidant x-PVP-N-oxide demonstrated comparable reactivity to pyridine-N-oxide in direct oxidation reactions of phosphines and phosphites in acetonitrile, but x-PVP-N-oxide did not react in other solvents. The polymer backbone of x-PVP-N-oxide, however, allowed for easy filtering and recycling in sequential oxidation reactions. In addition, x-PVP-N-oxide was tested as the stoichiometric oxidant in a copper-catalyzed OAT reaction to α-diazo-benzeneacetic acid methyl ester. The heterogeneous oxidant was much less reactive than pyridine-N-oxide, indicating that interaction with the metal catalyst was challenging. These results demonstrated a proof-of-concept that recyclable, polymer-supported OAT reagents could be a viable OAT reagents in direct oxidation reactions without metal catalysts.Graphical abstractGraphical abstract for this article
       
  • Triphenylene Based Metal-Pyridine Cages
    • Abstract: Publication date: Available online 23 September 2019Source: Tetrahedron LettersAuthor(s): Giacomo Berton, Tommaso Lorenzetto, Giuseppe Borsato, Paolo Sgarbossa, Claudio Santo, Fabiano Visentin, Fabrizio Fabris, Alessandro Scarso C3-symmetric pyridine containing tris-benzyl-O-substituted hexahydroxytriphenylene derivatives were prepared and used in combination with square-planar Pd(II) and Pt(II) complexes for the self-assembly of molecular cages in solution. The formation of a trigonal bipyramid M3L2 cage was demonstrated by multinuclear NMR analyses and pseudo 2D DOSY experiments and supported by semi-empirical calculations.Graphical abstractGraphical abstract for this article
       
  • Enantioselective synthesis of chiral carbocyclic pyrimidine nucleosides
           via asymmetric cyclopropanation
    • Abstract: Publication date: Available online 23 September 2019Source: Tetrahedron LettersAuthor(s): Hai-Xia Wang, Wen-Peng Li, Chao Xia, Ming-Sheng Xie, Gui-Rong Qu, Hai-Ming Guo An efficient method to construct chiral cyclopropyl pyrimidine carbocyclic nucleoside analogues bearing a quaternary center was developed via asymmetric Michael-initiated cyclopropanation. The axis chirality was observed in cyclopropyl pyrimidine carbocyclic nucleoside analogues for the first time, which was caused by the rotationally restricted NC bond in N-COPh moiety. Using (DHQD)2AQN as the organocatalyst, diverse cyclopropyl pyrimidine carbocyclic nucleoside analogues were generated in 76–93% yields and 73–96% ee.Graphical abstractGraphical abstract for this article
       
  • New strategy for the preparation of imidazole derivatives containing
           thiazole ring via ring opening/coupling/cyclization/decarboxylation
           cascade
    • Abstract: Publication date: Available online 23 September 2019Source: Tetrahedron LettersAuthor(s): Zahrasadat Golestaneh, Majid Ghashang The aim of this work is to investigate the three-component reaction of 6-aminopenicillinic acid, aldehydes and ammonium acetate. The work was used SiO2-H2SO4 as a catalyst to promote the reaction under solvent-free conditions. A series of 5,5-dimethyl-2-(2-aryl-1H-imidazol-5-yl)-2,5-dihydrothiazole derivatives were obtained as the main product by this method.Graphical abstractGraphical abstract for this article
       
  • Annulation Chemistry Based on Tandem Michael Addition-Enamine Formation
           – An Improved Method for the Preparation of
           1-Substituted-2,3,5,6,7,8-hexahydroquinolin-4(1H)-ones
    • Abstract: Publication date: Available online 23 September 2019Source: Tetrahedron LettersAuthor(s): Andrew Glass, Tyler Higgins, David A. Hunt The reaction of 2-(but-2-enoyl)cyclohexan-1-one 2 with primary amines affords 1-substituted-2,3,5,6,7,8-hexahydroquinolin-4(1H)-ones through a tandem Michael addition/enamine formation reaction sequence at room temperature in high yields. Reaction times are greatly reduced (4-24 h vs. 1-2 h; reflux versus room temperature) when powdered 4Å sieves are used.Graphical abstractGraphical abstract for this article
       
  • [1],+[5] diazonin-7-one+derivatives+via+arylation-allylation-RCM+pathway+of+anthranilamide+and+isatoic+anhydride&rft.title=Tetrahedron+Letters&rft.issn=0040-4039&rft.date=&rft.volume=">A facile synthesis of (Z)-1, 6-disubstituted-7H-benzo[b] [1],
           [5] diazonin-7-one derivatives via arylation-allylation-RCM pathway of
           anthranilamide and isatoic anhydride
    • Abstract: Publication date: Available online 21 September 2019Source: Tetrahedron LettersAuthor(s): Motakatla Novanna, Sathananthan Kannadasan, Ponnusamy Shanmugam A facile and efficient method has been developed for the synthesis of (Z)-6-allyl-1-phenyl-1,2,5,6-tetrahydro-7H-benzo[b][1], [5]diazonin-7-one and (Z)-1,6-diphenyl-1,2,5,6-tetrahydro-7H-benzo[b][1], [5]diazonin-7-one from anthranilamide via N-arylation/N-allylation and from isatoic anhydride via ring opening/N-arylation/N-allylation followed by ring closing metathesis using Grubbs-II catalyst as a key step. Grubbs-II catalyst was found to be superior over Grubbs-I catalyst in terms of reaction time and yield of the product, and the routes developed were suitable to synthesize benzo fused nine membered nitrogen heterocycles. The requirement of diallylated substrates with protected amine and amide nitrogen is suitable for RCM has been established for the synthesis of diazoninone deivatives.Graphical abstractGraphical abstract for this article
       
  • Visible-light-mediated direct access to α-ketoamides by dealkylative
           amidation of tertiary amines with benzoylformic acids
    • Abstract: Publication date: Available online 21 September 2019Source: Tetrahedron LettersAuthor(s): Zhiguo Zhang, Fangnan Liu, Jingwen Chen, Kai Zhou, Zongbi Bao, Baogen Su, Qiwei Yang, Qilong Ren, Yiwen Yang A visible-light induced direct amidation of benzoylformic acids with tertiary amines has been explored. Tertiary amines underwent N-dealkylative amidation with α-keto acid in the presence of [Ir{dFCF3ppy}2(bpy)]PF6 and Cs2CO3, affording the corresponding α-ketoamides in good yields under mild conditions. This transformation exhibits a wide substrate scope and provides a facile synthetic approach to α-ketoamides.Graphical abstractGraphical abstract for this article
       
  • Copper-catalyzed synthesis of oxime ethers from iminoxy radical (C=N-O•)
           and maleimides via radical addition
    • Abstract: Publication date: Available online 20 September 2019Source: Tetrahedron LettersAuthor(s): Ziwei Han, Subo Shen, Feng Zheng, Han Hu, Jianmin Zhang, Shizheng Zhu An efficient Cu(II)-catalyzed radical addition of maleimides has been achieved. The identified copper catalyst enables the formation of oxime radicals (N-O•) by cleaving the O-H bond in ketoximes, followed by the radical addition to N-substituted maleimides. The oxime radicals (N-O•) were detected and confirmed by EPR spectroscopy and variable-temperature 1H-NMR. The simple one-pot reaction realizes the facile preparation of a variety of oxime ether adduct products in moderate to good yields.Graphical abstractGraphical abstract for this article
       
  • Fluorescence properties of amido-substituted 2,3-naphthalimides:
           Excited-state intramolecular proton transfer (ESIPT) fluorescence and
           responses to Ca2+ ions
    • Abstract: Publication date: Available online 20 September 2019Source: Tetrahedron LettersAuthor(s): Lei Wang, Mayu Fujii, Misa Namba, Minoru Yamaji, Hideki Okamoto 2,3-Naphthalimide derivatives incorporating trifluoroacetamido (3a) and methansulfonamido (3b) functionalities at the 1-position were prepared and their intramolecular excited state proton transfer (ESIPT) fluorescence and responses to metal ions were investigated. Compound 3a displayed normal fluorescence in the amide form in toluene and MeCN and no response to metal cations in the corresponding amidate ion form. In contrast, compound 3b gave off dual emission assignable to normal and ESIPT fluorescence. Additionally, the amidate form of compound 3b displayed off-on fluorescence response to Ca2+.Graphical abstractGraphical abstract for this article
       
  • An efficient approach to isoquinoline via AgNO3-promoted 6-endo-dig
           cyclization followed by oxidative elimination of o-alkynylarylaldimines
           and its application in fluoride recognition
    • Abstract: Publication date: Available online 20 September 2019Source: Tetrahedron LettersAuthor(s): Yongxing Tang, Yajun Yu, Xinyu Wei, Jin Yang, Yeting Zhu, Yun-Hui Zhao, Zilong Tang, Zhihua Zhou, Xiaofang Li, Xianyong Yu A novel 6-endo-dig cyclization followed by oxidation/elimination of o-alkynylarylaldimines with 4-hydroxybenzylamine was developed for preparation of isoquinolines. The intermediates of this tandem reaction were monitored by mass spectroscopy (MS) to confirm the reaction pathway. This methodology was further applied to the design and synthesis of a novel ratiometric chemosensor for determination of fluoride.Graphical abstractGraphical abstract for this article
       
  • Base-Catalyzed Synthesis of Quinazolines in Aqueous Medium
    • Abstract: Publication date: Available online 19 September 2019Source: Tetrahedron LettersAuthor(s): Nagesh Jatangi, Palakodety Radha Krishna An alternative green protocol and step economy for the synthesis of quinazoline has been developed. The reaction of readily available 2-aminobenzonitriles with various organometallic reagents led to ortho-aminoaryl N-H ketimine species. The subsequent base catalysed N-C bond formation with various isothiocyanates afforded quinazoline scaffolds in aqueous medium. The salient features of this protocol are use of readily available inexpensive precursors, water as a green environmentally benign solvent, short reaction time, operational simplicity, easy workup procedure and good functional group tolerance.Graphical abstractGraphical abstract for this article
       
  • One-pot synthesis of 2-substituted thieno[3,2-b]indoles from
           3-aminothiophene-2-carboxylates through in situ generated
           3-aminothiophenes
    • Abstract: Publication date: Available online 19 September 2019Source: Tetrahedron LettersAuthor(s): Roman A. Irgashev, Alexander S. Steparuk, Gennady L. Rusinov A convenient protocol for one-pot synthesis of thieno[3,2-b]indoles, bearing aromatic, thien-2-yl or styryl fragments at C-2 position, from easily accessible 5-substituted 3-aminothiophene-2-carboxylates using the Fischer indolization reaction, was developed during this study. Two main steps of this approach are the saponification of the starting 3-aminoesters with sodium hydroxide and next treatment of the crude 3-aminoacids sodium salts with arylhydrazines in glacial acetic acid solution. The latter step includes in situ decarboxylation of the freed 3-aminothiophene-2-caboxylic acids to the 3-aminothiophenes and their acid promoted reaction with arylhydrazines to initially form arylhydrazones of 5-substituted thiophene-3(2H)-ones, which smoothly cause indolization to afford the desired thieno[3,2-b]indoles.Graphical abstractGraphical abstract for this article
       
  • Isatins 3-C Annulation vs Ring-opening: Two different Pathways for
           Synthesis of Spiro Compounds via Multicomponent Reactions
    • Abstract: Publication date: Available online 18 September 2019Source: Tetrahedron LettersAuthor(s): Qingqing Niu, Junhua Xi, Lei Li, Li Li, Chengli Pan, Meijun Lan, Liangce Rong An efficient synthesis of spiro compounds via two different pathways from the reactions of isatins, 3-phenylisoxazol-5(4H)-one (3-ethylisoxazol-5(4H)-one), and pyrazol-5-amine (6-aminopyrimidine-2,4(1H,3H)-dione) were reported. The catalyst Amberlyst-15 could be easy recycled and reused for many time without any appreciable loss in catalytic activity. The new type spiro compounds were gained through the ring-opening of isatins process. The structures of spiro[indoline-3,4'-isoxazolo[5,4-b]pyrazolo[4,3-e]pyridin]-2-one, spiro[isoxazolo[5,4-b]quino line-4,5'-pyrrolo[2,3-d]pyrimidine]-2',4',6'(1'H,3'H,7'H)-trione, and spiro[indoline-3,4'-pyrazolo[3,4-b]pyridine]-2,6'(5'H)-dione were successfully confirmed by 1H NMR, 13C NMR, HRMS, and X-ray crystal diffraction analysis.Graphical abstractGraphical abstract for this article
       
  • Dicitrinones E and F, Citrinin Dimers from the Marine Derived Fungus
           Penicillium citrinum HDN-152-088
    • Abstract: Publication date: Available online 18 September 2019Source: Tetrahedron LettersAuthor(s): Lu Wang, Changlong Li, Guihong Yu, Zichao Sun, Guojian Zhang, Qianqun Gu, Tianjiao Zhu, Qian Che, Huashi Guan, Dehai Li Two new citrinin dimers named dicitrinones E and F (1 and 2), together with one biogenetically related known citrinin monomer (3), were isolated from the marine derived fungus Penicillium citrinum HDN-152-088. All structures including the absolute configurations were elucidated on the basis of comprehensive spectroscopic data, and assisted by ECD calculations. Among them, compounds 1 and 2 belong to the class of citrinin dimers with a rare carbon-bridged C-7/C-7′ linkage. Compound 1 displayed antioxidant activity with IC50 value of 23.73 μM.Graphical abstractGraphical abstract for this article
       
  • Iron/Copper Co-Catalyzed Highly Selective Arylation of Sulfinamides with
           Aryl Iodides
    • Abstract: Publication date: Available online 18 September 2019Source: Tetrahedron LettersAuthor(s): Shuanglin Qin, Yunhao Luo, Yue Sun, Le Tian, Shende Jiang, Jun yan, Guang Yang In the present study, an inexpensive but efficient Iron(III) and Copper(II) co-catalyst without ligands catalyzed arylation of sulfinamides with aryl iodide was primarily reported. In brief, in the presence of Fe(NO3)3•9H2O, CuO and K3PO4, the highly selective C−N cross coupling of several sulfinamides and aryl iodides was achieved in high chemical yield, while the aryl chlorides and bromides could not yield coupling products. It is noteworthy that through the arylation of chiral tert-butanesulfinamide with aryl iodides, N-aryl tert-butanesulfinamides are provided without racemization, even in gram-scale. The possible mechanism was that This oxidative addition process between copper catalyst and aryl-iodides might be significantly accelerated by active Fe(III) species. Moreover, using this synthetic method, a facile and efficient access was developed for the derivatives of N-phenyl sulfinamides, which might help to develop new drug molecules and material chemicals.Graphical abstractGraphical abstract for this article
       
  • Synthesis and Antibacterial Activity of Four Natural Chalcones and Their
           Derivatives
    • Abstract: Publication date: Available online 17 September 2019Source: Tetrahedron LettersAuthor(s): Yuanyuan Li, Bingxia Sun, Jiadai Zhai, Lin Fu, Shuxin Zhang, Jing Zhang, Hongliang Liu, Wenhai Xie, Hongkuan Deng, Zhiwei Chen, Feng Sang Four natural chalcones bearing hydroxyisoprenyl or prenyl groups, named Paratocarpin E (2), Xanthoangelol D (3), Angusticornin A (4) and Kanzonol C (5), were prepared by employing the Claisen-Schmidt condensation as the key step. In an attempt to investigate the effect of the hydroxyisoprenyl group on biological activity, two of their derivatives were also prepared for antibacterial activity research. The synthesized compounds were investigated for their expected antibacterial activities against Gram positive bacteria (Bacillus subtilis, Staphylococcus aureus) as well as Gram negative bacteria (Escherichia coli, Pseudomonas aeruginosa). Paratocarpin E (2) was found to be the most potent against two Gram positive bacteria while the majority of the remaining compounds showed promising activity as well. However, all of the compounds were inactive against both Gram-negative bacteria.Graphical abstractGraphical abstract for this article
       
  • Nickel-catalyzed [2+2] cycloaddition reaction using bisallenes
    • Abstract: Publication date: Available online 17 September 2019Source: Tetrahedron LettersAuthor(s): Shigeru Arai, Yuna Kawata, Yuka Amako, Atsushi Nishida A nickel-catalyzed [2+2] cycloaddition of bisallenes has been described. Simple bisallenes are employed for the formation of “head to head” cycloadducts in the presence of Ni(0) with xantphos. The dienyl moiety in a product were applicable for various [4+2] cycloaddition reactions. Allene-allenamides under Ni-xantphos system gave the tricyclic compounds through sequential [2+2]–[4+2] cycloaddition reaction in highly stereoselective manner.Graphical abstractGraphical abstract for this article
       
  • CuI-catalyzed highly regioselective C-H functionalization of indoles using
           indole-3-tosylhydrazons as carbene precursor: An efficient synthesis of
           3,3-bis(indolyl)methane derivatives
    • Abstract: Publication date: Available online 17 September 2019Source: Tetrahedron LettersAuthor(s): Priya kamboj, Sunil Dutt, Sourav Chakroborty, Vikas Tyagi Herein, we have developed a novel approach for synthesizing symmetrical and unsymmetrical 3,3-bis(indolyl)methane derivatives via CuI-catalyzed C-H functionalization of indole using indole-3-tosylhydrazones as carbene precursor. This procedure works well with different substitutions such as NO2, Br, CH3 and OMe on indole or indole-3-tosylhydrazones and features high regioselectivity for C-3 functionalization over the C-1 and N-1 positions. Further, we have also revealed the feasibility of this protocol in a one-pot fashion starting from indole-3-carboxyaldehyde.Graphical abstractGraphical abstract for this article
       
  • A New Route to 1,2,3-Triazole Fused Benzooxazepine and Benzodiazepine
           Analogues Through Metal-free Intramolecular Azide-Olefin Oxidative
           Cycloaddition
    • Abstract: Publication date: Available online 17 September 2019Source: Tetrahedron LettersAuthor(s): D. Gangaprasad, J. Paul Raj, K. Karthikeyan, R. Rengasamy, M. Kesavan, M. Vajjiravel, J. Elangovan A collection of 1,2,3-Triazole fused benzooxazepine and benzodiazepine analogues was prepared by one pot azide substitution and intramolecular azide-olefin oxidative cycloaddition sequence under metal-free conditions.Graphical abstractGraphical abstract for this article
       
  • Talarophenol sulfate and talarophilones from the Australian mud dauber
           wasp-associated fungus, Talaromyces sp. CMB-W045
    • Abstract: Publication date: Available online 16 September 2019Source: Tetrahedron LettersAuthor(s): Pabasara Kalansuriya, Zeinab G. Khalil, Angela A. Salim, Robert J. Capon Chemical analysis of a jasmine rice cultivation of an Australian mud dauber wasp-associated fungus, Talaromyces sp. CMB-W045, led to the discovery of a new p-terphenyl, talarophenol sulfate (1). The structure elucidation of 1 was achieved by detailed spectroscopic analysis supported by acid hydrolysis to the p-hydroquinone talarophenol (2), and subsequent in situ air oxidation to trace amounts of the p-quinone talaroquinone (3). The same jasmine rice cultivation also yielded the new talarophilones A (4) and B (5), and known (+)-mitorubrin (6) and pochonin D (7), with structures assigned by detailed spectroscopic analysis. Neither 1 or 4-7 exhibited growth inhibitory properties against a panel of human cell lines, or bacterial or fungal pathogens, although 1 did exhibit selective antibacterial activity against Streptococcus pyogenes ATCC 12344 (IC50 10 µM).Graphical abstractGraphical abstract for this article
       
  • Stereoselective C-X and Regioselective C-H activation to, and selective
           C(sp2 )-C(sp3 ) reductive elimination from, platinum compounds with
           thiophene-derived ligands
    • Abstract: Publication date: Available online 16 September 2019Source: Tetrahedron LettersAuthor(s): Craig M. Anderson, Garrett Brown, Matthew W. Greenberg, David Yu, Nellie Bowen, Rahma Ahmed, Melissa Yost-Bido, Alina Wray Several thiophene-based N^C ligands were synthesized. Strategically, a bromide was incorporated on the 2-position of the thiophene ring. When allowed to react with the platinum tetramethyl dimer, [Pt2Me4(µ-SMe2)2], platinum(IV) platinacycles were formed by oxidative addition of the C(sp2)-X bond. These platinum(IV) compounds were characterized by NMR and HRMS. The platinum (IV) compounds were subsequently subjected to thermolysis. A series of reactions occurred, including selective C-C reduction elimination and selective C-H oxidative addition, giving mixtures of platinum(II) products with varying degrees of regioselectivity.Graphical abstractGraphical abstract for this article
       
  • Cephasinenoside A, a new cephalotane diterpenoid glucoside from
           Cephalotaxus sinensis
    • Abstract: Publication date: Available online 14 September 2019Source: Tetrahedron LettersAuthor(s): Chun-Xue Zhao, Bing-Qian Li, Zhao-Xiang Shao, Da-Hong Li, Yong-Kui Jing, Zhan-Lin Li, Hui-Ming Hua A new cephalotane diterpenoid glucoside, cephasinenoside A (1), was isolated from the twigs and leaves of Cephalotaxus sinensis (Rehd. et Wils.) Li. The structure of 1 was established on the basis of spectroscopic analyses and ECD calculations. Compound 1 represents the first cephalotane diterpenoid glycoside which inhibits the proliferation of human acute myeloid leukemia HL-60 cells with a GI50 value of 7.17 ± 1.03 μM.Graphical abstractCephasinenoside A is the first cephalotane diterpenoid glucoside isolated from Cephalotaxus sinensis. It was active against HL-60 cells with GI50 value of 7.17 ± 1.03 μM. The structure including absolute configuration was elucidated based on spectroscopic analyses and calculated ECD methods.Graphical abstract for this article
       
  • Visible-light-promoted organic dye catalyzed perfluoroalkylation of
           hydrazones under mild conditions
    • Abstract: Publication date: Available online 6 September 2019Source: Tetrahedron LettersAuthor(s): Ming-Dong Zhou, Zhen Peng, Lei Li, He Wang A general and facile visible-light-promoted organic dye catalyzed perfluoroalkylation of hydrazones has been developed using inexpensive and non-toxic Eosin Y as the photoredox catalyst under mild conditions. This reaction protocol exhibits synthetic simplicity, broad scope of substrates, and excellent functional group compatibility. A gram scale synthesis can be also facilitated with a satisfactory yield, which opens up the possibility of practical applications.Graphical abstractGraphical abstract for this article
       
  • A novel approach to biologically relevant
           oxazolo[5,4-d]pyrimidine-5,7-diones via readily available diazobarbituric
           acid derivatives
    • Abstract: Publication date: Available online 6 September 2019Source: Tetrahedron LettersAuthor(s): Martha Gecht, Grigory Kantin, Dmitry Dar'in, Mikhail Krasavin An alternative route from 1,3-disubstituted barbituric acids to biologically relevant oxazolo[5,4-d]pyrimidine-5,7-diones was developed that features sulfonyl-azide-free (SAFE) diazo transfer and Rh2(esp)2-catalyzed cycloaddition of the resulting 5-diazobarbituric acids with aliphatic and aromatic nitriles. Besides being shorter compared to the previously described approaches, the method allows introduction of alkyl substituents at the 1,3-oxazole ring of the fused heterocyclic system.Graphical abstractGraphical abstract for this article
       
 
 
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