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Tetrahedron Letters
Journal Prestige (SJR): 0.683
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  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 0040-4039 - ISSN (Online) 1359-8562
Published by Elsevier Homepage  [3162 journals]
  • Graphical abstract TOC
    • Abstract: Publication date: 8 August 2018Source: Tetrahedron Letters, Volume 59, Issue 32Author(s):
       
  • Graphical abstract TOC cont’d
    • Abstract: Publication date: 8 August 2018Source: Tetrahedron Letters, Volume 59, Issue 32Author(s):
       
  • Graphical abstract TOC
    • Abstract: Publication date: 8 August 2018Source: Tetrahedron Letters, Volume 59, Issue 32Author(s):
       
  • Synthesis of (Z)-Nitroalkene Derivatives through Oxidative Dehydrogenation
           Coupling of α-Aminocarbonyl Compounds with Nitromethane by Copper
           Catalysis
    • Abstract: Publication date: Available online 12 July 2018Source: Tetrahedron LettersAuthor(s): Menghua Zhu, De Chen, Sheng Zeng, Chenhu Xing, Wei Deng, Jiannan Xiang, Rui-Jia Wang A novel copper-catalyzed cross-dehydrogenative coupling reaction of α-amino carbonyl compounds with nitromethane to synthesis of (Z)-nitroalkene derivatives has been established. (Z)-Nitroalkene derivatives are achieved through the cleavage of sp3 C-H bonds and formation of C-C double bond, with mild reaction conditions and excellent stereoselectivity.Graphical abstractGraphical abstract for this article
       
  • Graphical abstract TOC
    • Abstract: Publication date: 1 August 2018Source: Tetrahedron Letters, Volume 59, Issue 31Author(s):
       
  • Graphical abstract TOC
    • Abstract: Publication date: 1 August 2018Source: Tetrahedron Letters, Volume 59, Issue 31Author(s):
       
  • Asymmetric synthesis of highly functionalized tyrosine derivatives for the
           construction of bistetrahydroisoquinoline alkaloids
    • Abstract: Publication date: 1 August 2018Source: Tetrahedron Letters, Volume 59, Issue 31Author(s): Enming Du, Xuan Pan, Baohe Guan, Zhanzhu Liu A novel and facile synthesis of l-5-hydroxy-2,4-methoxy-3-methylphenylalanine derivatives, which are the key coupling partners for the asymmetric total synthesis of natural bistetrahydroisoquinoline alkaloids, is realized starting from l-tyrosine with 17% overall yield. The synthesis has been carried out on a multigram scale featuring the following key steps: (a) transformation of phenol to dihydroquinone via salcomine-catalyzed oxidation followed by zinc-acetic acid reduction; (b) single TBS-protection of dihydroquinone; (c) Mitsunobu methylation of the newly generated phenolic hydroxyl group.Graphical abstractGraphical abstract for this article
       
  • Amidation strategy for final-step α-hydroxytropolone diversification
    • Abstract: Publication date: 1 August 2018Source: Tetrahedron Letters, Volume 59, Issue 31Author(s): Alex J. Berkowitz, Rudolf G. Abdelmessih, Ryan P. Murelli α-Hydroxytropolones (αHTs) are excellent metalloenzyme-inhibiting fragments that have been the basis for the development of potent inhibitors of various therapeutically important enzymes. The following manuscript describes a final-step amidation approach for αHT diversification. The method takes advantage of a scalable, chromatography-free synthesis of a carboxylic acid-appended αHT, and the present manuscript describes the conversion of this compound to eight amide-containing αHTs, three of which should be useful as chemical probes. This general strategy is expected to find widespread usage in both chemical biology and medicinal chemistry studies on αHTs.Graphical abstractGraphical abstract for this article
       
  • A red emissive donor-acceptor fluorophore as protein sensor: Synthesis,
           characterization and binding study
    • Abstract: Publication date: 1 August 2018Source: Tetrahedron Letters, Volume 59, Issue 31Author(s): Rajib Choudhury, Hope E. Parker, Kassandra M. Cendejas, Kalie L. Mendenhall The rational design of environmentally sensitive small molecule fluorophores with superior photophysical properties is critical for fluorimetry based biosensing. Herein, we have developed a new donor-acceptor fluorophore for quantitative detection of Human Serum Albumin (HSA) in aqueous samples. The fluorophore was easily prepared by Knoevenagel condensation, and showed excellent photophysical properties and positive solvatochromism. The design of the fluorophore was based on a nitrogen donor—π-conjugation—nitrile acceptors (D—π—A) to preserve efficient intramolecular charge transfer and long-wavelength emission. The fluorophore showed remarkable “turn-on” fluorescence in presence of HSA, which led to quantitative determination of the protein in aqueous buffer samples. Structure and electronic properties of the fluorophore played important roles on the superior HSA sensing ability. The findings indicate that minor changes in design strategy can be advantageous while developing long-wavelength (far red or near infrared) emitting fluorophores for biosensing and bioimaging.Graphical abstractGraphical abstract for this article
       
  • A green protocol for one pot synthesis of benzosuberone tethered
           thiadiazolopyrimidine-6-carboxylates using PEG-400 as potent
           anti-proliferative agents
    • Abstract: Publication date: 1 August 2018Source: Tetrahedron Letters, Volume 59, Issue 31Author(s): Suresh Kasaboina, Rajitha Bollu, P. Mary Gomedhika, Venkatesh Ramineni, Lingaiah Nagarapu, Naresh Dumala, Paramjit Grover, Jagadeesh Babu Nanubolu A new concise and facile method was explored to synthesize a collection of new benzosuberone based thiadiazolo [3,2-a] pyrimidine-6-carboxylates using polyethylene glycol (PEG), which could be regarded as the derivatives of the hybrid scaffolds of bioactive natural benzosuberone and heterocyclic thiadiazolo[3,2-a]pyrimidine. The structures of the synthesized compounds were characterized by 1H, 13C NMR, MS and IR; and their anti-proliferative activity was evaluated against four human cancer cell lines; A549, SKNSH, HeLa and MCF-7. Among the tested compounds, compound 8k showed the most prominent activity against all the cell lines and these results may lay the foundation for further design of novel anti-proliferative agents.Graphical abstractDesign strategy for 2,3-dimethylbenzocycloheptenone tethered thiadiazolo-pyrimidine carboxylates (8a–k).Graphical abstract for this article
       
  • Catalytic alkenylation of γ-substituted butenolides with cyclic
           N-sulfonylated imines in water leading to α-arylidene butenolide
           derivatives
    • Abstract: Publication date: 1 August 2018Source: Tetrahedron Letters, Volume 59, Issue 31Author(s): Feng Li, Jingjing Wang, Wenlong Pei, Hai Ma, Hong Li, Mingyue Cui, Shuxin Peng, Shihui Wang, Lantao Liu An efficient Et3N-catalyzed alkenylation of γ-substituted deconjugated butenolides with cyclic N-sulfonylated imines in water is described. The reaction proceeds efficiently under mild reaction conditions to give α-arylidene butenolide derivatives in high yield (82–96%).Graphical abstractGraphical abstract for this article
       
  • Lewis acid-mediated mono- and bis-addition of C-nucleophiles to
           1,3-dioxolan-4-ones
    • Abstract: Publication date: 1 August 2018Source: Tetrahedron Letters, Volume 59, Issue 31Author(s): Vitaly A. Shcherbinin, Valery V. Konshin The reactions of 1,3-dioxolan-4-ones, readily available from α-hydroxy acids and aldehydes, with C-nucleophiles are described. Two possible reaction pathways resulting in O-substituted acids and tri-(hetero)arylmethanes are shown.Graphical abstractGraphical abstract for this article
       
  • A phosphonated copillar[5]arene: Synthesis and application in the
           construction of pH-responsive supramolecular polymer in water
    • Abstract: Publication date: 1 August 2018Source: Tetrahedron Letters, Volume 59, Issue 31Author(s): Zhihua Zhang, Li Shao, Jie Yang A phosphonated-functionalized copillar[5]arene was designed and synthesized. 1H NMR, 13C NMR, ESI-MS and HR-MS were performed to provide converging evidences of the structure of obtained copillar[5]arene. Driven by hydrophobic interactions and C–H···π interactions between the decyl moiety and the pillar[5]arene cavity, a pH-responsive linear supramolecular polymer was fabricated from this phosphonate-functionalized AB type monomer in water. Concentration-dependent 1H NMR, NOESY, DOSY, and specific viscometry were carried out to study the supramolecular polymerization process.Graphical abstractGraphical abstract for this article
       
  • Phenoxy-benzothiadiazole dyes: Synthesis, photophysical properties and
           preliminary application in OLEDs
    • Abstract: Publication date: 1 August 2018Source: Tetrahedron Letters, Volume 59, Issue 31Author(s): Alessandra Pazini, Luis Maqueira, Harold C. Avila, Felipe M. Valente, Rian E. Aderne, Davi Back, Ricardo Q. Aucélio, Marco Cremona, Jones Limberger The synthesis of a phenoxy-benzothiadiazole (BTD) derivative is reported for the first time. This derivative was employed as an intermediate in the obtention of two novel highly fluorescent aryl-phenoxy-BTD dyes. Their photophysical properties were evaluated in solution and the results indicate a strong intramolecular charge transfer (ICT) character in the excited state. The luminophore 3a, possessing a donor-BTD-phenoxide architecture, exhibits superior fluorescence quantum yield (0.67) than the designed acceptor-BTD-phenoxide dye (0.06). After electrochemical and photoluminescence characterization of thin films of 3a, an OLED with the configuration ITO/PEDOT:PSS/3a/TPBi/LiF/Al was constructed. This device displayed a green emission centered at 547 nm, with CIE coordinates of (0.40, 0.55). For comparison, an OLED using a previously reported luminescent BTD-pyridyl derivative was also constructed. The OLED made with the phenoxy-BTD derivative operated using less current density and led to higher irradiance and electrical stability, indicating the high potential of ArO-BTD dyes for future application in electroluminescent devices.Graphical abstractGraphical abstract for this article
       
  • Sublimable bis(β-iminoenolate)palladium(II) complexes and their
           application as catalysts in Suzuki-Miyaura reactions
    • Abstract: Publication date: 1 August 2018Source: Tetrahedron Letters, Volume 59, Issue 31Author(s): Mi Jin Kim, Myung Jin Jung, Yeong Joon Kim, Ha Kyoung Sung, Ju Young Lee, Sung Jin Ham, Chan Pil Park The Pd(II) complexes strongly chelated by two β-iminoenolate ligands were easily synthesized in only two steps, and purified based on their sublimable and highly stable property. The Pd(II) complexes anchored on a silica surface showed good catalytic activity in Suzuki-Miyaura reactions (up to 99% yield with 0.05 mol% catalyst). They tolerated a wide range of temperature (rt∼110 °C) and various solvents, and could be reused multiple times after simple recovering process.Graphical abstractGraphical abstract for this article
       
  • Revisiting Amadori and Heyns synthesis: Critical percentage of acyclic
           form play the trick in addition to catalyst
    • Abstract: Publication date: 1 August 2018Source: Tetrahedron Letters, Volume 59, Issue 31Author(s): Debasree Chanda, Nanishankar V. Harohally Amadori and Heyns reaction are landmark reactions of carbohydrate chemistry. Synthesis of simple Amadori and Heyns compounds are complicated by various factors and require tedious column chromatographic or ion chromatographic separations. Herein, we report an improved catalytic method based on classical synthetic method of Amadori and Heyns compounds in light of new understanding of a factor governing the reaction. By utilizing the improved catalytic method, we have accomplished several Amadori compounds of d-tagatose and also numerous other Amadori and Heyns compounds.Graphical abstractGraphical abstract for this article
       
  • Synthesis of quinolines from anilines, acetophenones and DMSO under air
    • Abstract: Publication date: 1 August 2018Source: Tetrahedron Letters, Volume 59, Issue 31Author(s): Tao-Shan Jiang, Xi Wang, Xiuli Zhang An efficient CH3SO3H-promoted synthesis of quinolines from readily available anilines, acetophenones and DMSO under air is reported. This protocol gives diverse substituted 4-arylquinolines in moderate to high yields with broad substrate/functional group tolerance. Preliminary mechanistic studies demonstrate that DMSO may be transformed to HCHO in this process and used as a one carbon source.Graphical abstractGraphical abstract for this article
       
  • Cage-like monoterpenoid indole alkaloids with antimicrobial activity from
           Alstonia scholaris
    • Abstract: Publication date: 1 August 2018Source: Tetrahedron Letters, Volume 59, Issue 31Author(s): Hao-Fei Yu, Wan-Yi Huang, Cai-Feng Ding, Xin Wei, Lan-Chun Zhang, Xu-Jie Qin, Hong-Xia Ma, Zi-Feng Yang, Ya-Ping Liu, Rong-Ping Zhang, Xin-Hua Wang, Xiao-Dong Luo Three new cage-like monoterpenoid indole alkaloids, scholarisines T–V (1–3), together with three known analogues 4–6 were isolated from the leaves of Alstonia scholaris. Among them, 2 represents a unique degraded derivative, whereas 3 shares a rare 5,16-seco lactone scaffold. The structures were mainly established by extensive spectroscopic data analyses, and their plausible biosynthesis pathway from picrinine were proposed. Compared with positive control cefotaxime, alkaloid 2 showed remarkable antibacterial activity against Bacillus subtilis with an MIC value of 3.12 μg/mL, whereas 1–3 exhibited significant antibacterial effects on Escherichia coli with an MIC value of 0.78 μg/mL.Graphical abstractGraphical abstract for this article
       
  • Synthesis of new indolylpyrrole derivatives via a four-component domino
           reaction between arylglyoxals, acetylacetone, indole and aliphatic amines
           in aqueous media
    • Abstract: Publication date: 1 August 2018Source: Tetrahedron Letters, Volume 59, Issue 31Author(s): Fereshteh Mousavizadeh, Mahdiyeh Talebizadeh, Mohammad Anary-Abbasinejad A novel synthesis of indolylpyrrole derivatives is described by a four-component domino reaction between arylglyoxals, acetylacetone, indole and aliphatic amines in water as solvent at 60 °C without using any catalyst or promoter. The FT-IR, 1H NMR, 13C NMR spectral and elemental analysis confirm the structures of the products.Graphical abstractGraphical abstract for this article
       
  • Direct, oxidative halogenation of diaryl- or dialkylphosphine oxides with
           (dihaloiodo)arenes
    • Abstract: Publication date: 1 August 2018Source: Tetrahedron Letters, Volume 59, Issue 31Author(s): Jasmin Eljo, Graham K. Murphy The oxidative halogenation of diaryl- or dialkylphosphine oxides with the hypervalent iodine reagents (difluoroiodo)toluene (p-TolIF2, 1) and (dichloroiodo)benzene (PhICl2, 2) is reported. Phosphoric fluorides could be recovered in 32–75% yield, or they could be trapped with EtOH to give the corresponding phosphinate in typically good yield. Phosphoric chlorides were not readily isolable, and were trapped with alcohol and amine nucleophiles, giving diaryl- or dialkylphos-phinates and phosphinamides in up to 90% yield.Graphical abstractGraphical abstract for this article
       
  • Synthesis of electron-deficient (Sa,R,R)-(CF3)2-C3-TunePhos and its
           applications in asymmetric hydrogenation of α-iminophosphonates
    • Abstract: Publication date: 1 August 2018Source: Tetrahedron Letters, Volume 59, Issue 31Author(s): Huan-Ping Xie, Zhong Yan, Bo Wu, Shu-Bo Hu, Yong-Gui Zhou A novel electron-deficient chiral diphosphine ligand bearing trifluoromethyl groups at the 6- and 6′-positions of the biphenyl backbone, (Sa,R,R)-(CF3)2-C3-TunePhos, has been synthesized from the commercially available chiral 2,4-pentanediol. The above ligand was successfully applied to palladium-catalyzed asymmetric hydrogenation of linear and cyclic α-iminophosphonates with up to 99% ee.Graphical abstractGraphical abstract for this article
       
  • Recent development of ortho-C–H functionalization of aryl sulfoxides
           through [3,3] sigmatropic rearrangement
    • Abstract: Publication date: 1 August 2018Source: Tetrahedron Letters, Volume 59, Issue 31Author(s): Tomoyuki Yanagi, Keisuke Nogi, Hideki Yorimitsu Sulfoxide-promoted ortho-C–H functionalization reactions of aromatic compounds have emerged as powerful tools for organic synthesis. Among them, [3,3] sigmatropic rearrangement induced by interrupted Pummerer reaction or electrophilic activation of sulfoxides has proved to be a fruitful strategy due to its versatility and high reaction efficiency. This digest paper mainly focuses on recent progress on C–H functionalization reactions of aryl sulfoxides via [3,3] sigmatropic rearrangement of sulfonium-tethered intermediates.Graphical abstractGraphical abstract for this article
       
  • Graphical abstract TOC cont’d
    • Abstract: Publication date: 1 August 2018Source: Tetrahedron Letters, Volume 59, Issue 31Author(s):
       
  • Corrigendum to “A multicomponent access to
           1,3-thiazine-6-phenylimino-5-carboxylates” [Tetrahedron Lett. 57 (2016)
           3256–3259]
    • Abstract: Publication date: Available online 11 July 2018Source: Tetrahedron LettersAuthor(s): Trieu N. Trinh, Adam McCluskey
       
  • Total Synthesis and Biological Evaluation of Nannocystin Analogues
           Modified at the Polyketide Phenyl Moiety
    • Abstract: Publication date: Available online 10 July 2018Source: Tetrahedron LettersAuthor(s): Yunfeng Tian, Yahui Ding, Xiaolong Xu, Yanju Bai, Yang Tang, Xin Hao, Weicheng Zhang, Yue Chen Total synthesis of a focused set of 10 nannocystin analogues 3a-3j modified at the polyketide phenyl moiety was reported. These compounds were evaluated against three cancer cell lines. Compared with the naturally occurring congener 3a, the other synthetic variants either preserved or lose antiproliferative activity at varying degrees. Moreover, the potent analogues also displayed comparable levels of cytotoxicity toward two normal cell lines.Graphical abstractGraphical abstract for this article
       
  • Reaction-based fluorescent probe for detecting of sulfur dioxide
           derivatives and hydrazine via distinct emission signals
    • Abstract: Publication date: Available online 10 July 2018Source: Tetrahedron LettersAuthor(s): Yang Zhou, Fanwei Zeng, Yang Liu, Meng Li, Shuzhang Xiao, Jiaying Yan, Nuonuo Zhang, Kaibo Zheng Recently, the construction of multiple analytes responsive fluorescent probes with distinct emission signals has attracted widely attention. Thus, we have designed and synthesized a new fluorescent probe, 2-(2-hydroxyphenyl)benzothiazole dye skeleton (HBT-1), for the detection of sulfur dioxide and hydrazine. Significant fluorescence enhancements in two distinct emission bands (λem= 464 nm and 498 nm) were generated when HBT-1 reacted with sulfur dioxide derivatives or hydrazine, respectively. Furthermore, the probe HBT-1 response can be saturated surpurisingly at the low concentration (100 μM), shorter reaction time for sulfur dioxide derivatives, while a longer reaction time and greater concentration (400 μM) for hydrazine. In other words, the probe HBT-1 can detect sulfur dioxide derivatives without hydrazine interference at low analyte concentrations.Graphical abstractGraphical abstract for this article
       
  • Synthesis and Cytotoxicity Screening of derivatives of the simplified
           ecteinascidin pentacyclic skeleton as Anticancer Agents
    • Abstract: Publication date: Available online 10 July 2018Source: Tetrahedron LettersAuthor(s): Ju Guo, Yang yang, Nan Wang, Zhanzhu Liu A series of new ecteinascidin pentacyclic-derived compounds bearing aryl carboxylic amide side chains at C-22 have been designed and synthesized. The cytotoxicity evaluation confirmed their potent antitumor activity by use of eight different cell lines. Studies on the structure-activity relationship of them showed that the chemical structure of C-22 pendants have great effects on the tumor-killing activity. Notably, Compounds 6, 7 and 8 with benzo[b]thiophene-2-carboxamide pendants exhibited excellent broad-spectrum antitumor activity with the low IC50 values of 10-7 M.Graphical abstractGraphical abstract for this article
       
  • Redox-neutral C−H cyanation of tetrahydroisoquinolines under photoredox
           catalysis
    • Abstract: Publication date: Available online 10 July 2018Source: Tetrahedron LettersAuthor(s): Takafumi Ide, Kazunori Shimizu, Hiromichi Egami, Yoshitaka Hamashima Redox-neutral cyanation of C−H bond adjacent to a nitrogen atom was achieved by using the combination of a photoredox catalyst and p-toluenesulfonyl cyanide. The reaction of tetrahydroisoquinolines porceeded smoothly, affording the corresponding cyanated products selectively in good to high yield. Although the reaction rate became slower in the case of the substrates having electron-withdrawing groups, high yields were achieved by elongating the reaction time. Although the yields were only moderate, the reaction conditions were also applicable to N,N-dialkylanilines.Graphical abstractGraphical abstract for this article
       
  • Dual probing of redox species, NAD(P)H and HOCl, with a
           benzo[a]phenoxazine-based far red-emitting dye
    • Abstract: Publication date: Available online 10 July 2018Source: Tetrahedron LettersAuthor(s): Mithun Santra, Sourav Sarkar, Yong Woong Jun, Ye Jin Reo, Kyo Han Ahn We report a benzo[a]phenoxazine-based far red-emitting probe which selectively senses reduced nicotinamide adenine dinucleotide (NADH) and its phosphate ester NADPH, the most indispensable coenzymes found in all living cells, with “turn-off” fluorescence response at 650 nm. The original probe can be regenerated quantitatively through oxidation using hypochlorous acid, a reactive oxygen species, which was accompanied by restored fluorescence at 650 nm. This probe was also applied for fluorescence imaging of NADH in HeLa cells.Graphical abstractGraphical abstract for this article
       
  • Spiropyran-azobenzene-DBU System as Solvent Indicator
    • Abstract: Publication date: Available online 10 July 2018Source: Tetrahedron LettersAuthor(s): Zhiping Xu, Shen Li, Yujun Shen, Meijun Chen, Xusheng Shao A dyad bearing azobenzene and spiropyran units was synthesized and its applications in indicating the polarity and protic or aprotic properties of a solvent were explored. The spiropyran-azobenzene derivative (SPAB) can be induced to different forms in different miscellaneous solvents accompanied with different color changes and spectral characteristics at the presence of organic base DBU. In a nonpolar or low-polar solvent, SPAB exists in thermostable spiropyran form with yellow color output. While in an aprotic polar solvent, the spiropyran part isomerized to merocyanine form giving a blue color. When SPAB is subjected to a protic solvent, the alkylation reaction occurs at the oxygen generating the alkylated-SPAB with red color. This solvent-dependent property can be used for discriminating solvent type.Graphical abstractGraphical abstract for this article
       
  • Direct synthesis of 6-sulfonylated phenanthridines via silver-catalyzed
           radical sulfonylation-cyclization of 2-isocyanobiphenyls
    • Abstract: Publication date: Available online 9 July 2018Source: Tetrahedron LettersAuthor(s): Manjula Singh, Arvind K. Yadav, Lal Dhar S. Yadav, Rana Krishna Pal Singh A convenient and straightforward synthesis of 6-sulfonylated phenanthridines via silver-catalyzed sequential radical insertion, cyclization and aromatization of 2-isocyanobiphenyls is reported. The protocol does not require a phenanthridine scaffold as a substrate and presents a highly regioselective synthesis of 6-alkyl/arylsulfonyl phenanthridines. The protocol utilizes readily available and easy to handle sodium sulfinates as sulfonating agents and potassium persulfate as an oxidant to afford good to excellent yields of the desired products in a one-pot operation at room temperature.Graphical abstractGraphical abstract for this article
       
  • TfOH Catalyzed Synthesis of 1-Substituted Tetrahydrocarbazoles
    • Abstract: Publication date: Available online 9 July 2018Source: Tetrahedron LettersAuthor(s): Laxmi Narayan Nanda, Vipin Rangari Synthesis of 1-substituted tetrahydrocarbazole is accomplished by TfOH catalyzed reaction of 3-substituted indoles tethered with secondary and tertiary alcohols. The reaction was generalized for a variety of substrates and was extended to the synthesis of 2,3,3a,6-tetrahydro-1H-pyrido[3,2,1-jk]carbazole and carbazoles.Graphical abstractGraphical abstract for this article
       
  • Metal-free, PTSA catalyzed facile synthesis of β-ketoacetal from
           β-chlorocinnamaldehyde
    • Abstract: Publication date: Available online 7 July 2018Source: Tetrahedron LettersAuthor(s): Avinash K. Srivastava, Munsaf Ali, Kamal Nayan Sharma, Raj K. Joshi A toluene solution of β-chlorocinnamaldehyde and dihydroxy alcohols in the catalytic presence of para-toluenesulphonic acid (PTSA) yield the β-ketoacetal in good to outstanding amount. The catalyst (PTSA), first selectively protect the aldehydic group to form the β-chloroacetal and the subsequent dechlorination by H2O result the β-ketoacetal. A significant transformation was achieved with electron donating substituent attached at the β-position of cinnamaldehyde. The selective formation of β-keto-1,3-acetal was also obtained with a mixture of 1, 2- and 1, 3- diol. The present reaction consists a metal-free, economical, robustly feasible, sizeable functional group tolerance and high yield properties. Moreover, the use of different dihydroxy alcohols made this process more benign and valuable towards the metal-free development of ketones. First of its kind, a rare and unusual multitasking nature of PTSA is observed.Graphical abstractGraphical abstract for this article
       
  • One-pot synthesis of 2,3-disubstituted benzofurans from 2-chlorophenols
           using palladium–dihydroxyterphenylphosphine catalyst
    • Abstract: Publication date: Available online 6 July 2018Source: Tetrahedron LettersAuthor(s): Miyuki Yamaguchi, Hayato Ozawa, Haruka Katsumata, Tomoyo Akiyama, Kei Manabe 2,3-Disubstituted benzofurans possessing 2-hydroxyphenyl moiety at the C-3 position were synthesized from readily available 2-chlorophenols and terminal alkynes by hydroxy-directed ortho-Sonogashira coupling and subsequent oxypalladation/reductive elimination, using Pd-dihydroxyterphenylphosphine catalyst. The catalyst accelerates not only the Sonogashira coupling but also the introduction of 2-hydroxyphenyl group at the C-3 position of benzofuran.Graphical abstractGraphical abstract for this article
       
  • Decarboxylative difluoromethylation of aldehydes with PhSO2CF2COOK: A
           facile and efficient access to difluoromethylated carbinols
    • Abstract: Publication date: Available online 6 July 2018Source: Tetrahedron LettersAuthor(s): Yu-Jun Zhu, Zhong-Liang Lei, Da-Kang Huang, Bo Lian, Zhen-Jiang Liu, Xiao-Jun Hu, Jin-Tao Liu A novel decarboxylative difluoromethylation reaction of PhSO2CF2COOK with aldehydes under metal- and ligand-free conditions has been developed. The reaction is very mild and tolerates a wide range of aldehydes (both enolizable and non-enolizable aldehydes), providing a facile and efficient method for the synthesis of structurally diverse difluoromethylated carbinols in moderate to excellent yields.Graphical abstractGraphical abstract for this article
       
  • Asymmetric Synthesis and Antiviral Activity of Novel Chiral
           Amino-Pyrimidine Derivatives
    • Abstract: Publication date: Available online 6 July 2018Source: Tetrahedron LettersAuthor(s): Song Bai, Shan Liu, Yunying Zhu, Qin Wu By using a chiral cinchona alkaloid-squaramide catalyst, a series of both enantiomers of novel amino-pyrimidine derivatives can be obtained in an enantioselective three-component one-pot Mannich reaction with high yields and excellent enantioselectivities. In addition, these chiral derivatives were found to exhibit higher antiviral activities against tobacco mosaic virus (TMV) in vivo than the commercial agent ningnanmycin. In particular, chiral compounds (R)-4b and (R)-4e showed excellent antiviral activity against TMV at a concentration of 500 μg/mL, with a curative activity of 56.8% and 55.2%, respectively, a protection activity of 69.1% and 67.1%, respectively, and an inactivation activity of 91.5% and 94.3%, respectively. These values are superior to those of the agent ningnanmycin (which has curative, protective, and inactivation activities of 52.9%, 62.8%, and 90.4%, respectively). The antiviral mechanisms and enhanced antiviral activities of these chiral derivatives are interesting subjects for future investigation.Graphical abstractGraphical abstract for this article
       
  • Palladium/copper-catalyzed tandem Sonogashira coupling/lactonization of
           methyl 2-(2′,2′-dibromovinyl)benzoate with terminal alkynes: Facile
           access to 3-alkynyl isocoumarins
    • Abstract: Publication date: Available online 6 July 2018Source: Tetrahedron LettersAuthor(s): Xiaozu Liu, Guojun Chen, Yuxiang Zhou, Peijun Liu An efficient palladium/copper-catalyzed tandem Sonogashira reaction/lactonization of methyl 2-(2′,2′-dibromovinyl)benzoate with terminal alkynes has been developed. This facile and direct approach furnishes a variety of 3-alkynyl isocoumarins in moderate to good yields under mild reaction conditions. Furthermore, this method enables concise total synthesis of natural products 3′-hydroxycorfin and gymnopalynes A.Graphical abstractGraphical abstract for this article
       
  • Facile synthesis of S-arylisothioureas via the S-arylation of
           arylthioureas with aryl iodides in water
    • Abstract: Publication date: Available online 5 July 2018Source: Tetrahedron LettersAuthor(s): Xing Liu, Hui Zhu, Shi-Bo Zhang, Yu Cheng, Han-Ying Peng, Zhi-Bing Dong An environmentally benign, simple and highly efficient protocol for the synthesis of S-arylisothiourea derivatives has been achieved in good to excellent yields by reacting a series of aryl iodides with arylthioureas, using inexpensive CuSO4·5H2O as catalyst in water without PTC (phase transfer catalyst). The protocol features easy performance, good to excellent yields, good tolerance towards a variety of functional groups, which could be useful for the preparation of some biologically active compounds.Graphical abstractGraphical abstract for this article
       
  • Heterogeneous catalytic 1,4-addition of arylmagnesium compounds to
           chalcones
    • Abstract: Publication date: Available online 4 July 2018Source: Tetrahedron LettersAuthor(s): Kinga Juhász, Zoltán Hell Copper(II) on a 4 Å molecular sieve support catalyses the chemoselective addition of alkyl- and arylmagnesium halides to chalcones. Only the 1,4-addition products were obtained in high yields.Graphical abstractGraphical abstract for this article
       
  • Release of small molecules from aggregates consisting of an amphiphilic
           oligonucleotide functionalized by a photochromic azobenzene unit
    • Abstract: Publication date: Available online 4 July 2018Source: Tetrahedron LettersAuthor(s): Takuma Itagaki, Ryohsuke Kurihara, Kazuhito Tanabe Stimuli-responsive nanocarriers offer favorable properties for the target-specific delivery of drugs. Herein, we employed photoirradiation as an external stimulus for the construction of a molecular system that encapsulated small molecules, which were released upon photoirradiation. These nanocarriers consisted of DNA amphiphiles (ODAz 1), in which an oligodeoxynucleotide and an alkyl chain were employed as the hydrophilic and hydrophobic parts, respectively, and these two parts were linked by a photochromic azobenzene unit. In aqueous solutions, ODAz 1 formed nanosized aggregates that encapsulated hydrophobic molecules in their hydrophobic core. Photoirradiation induced isomerization of the azobenzene unit led to changes in aggregate size and the immediate release of the molecules. The aggregate smoothly penetrated the cell membrane, and the photochemical release and delivery of small molecules into living cells were achieved. Thus, ODAz 1 aggregates represent promising photosensitive nanocarriers that may be applicable to drug delivery and targeting.Graphical abstractGraphical abstract for this article
       
  • Room temperature dehalogenation of (hetero)aryl halides with
           magnesium/methanol
    • Abstract: Publication date: Available online 4 July 2018Source: Tetrahedron LettersAuthor(s): Jabrane Jouha, Mostafa Khouili, Marie-Aude Hiebel, Gérald Guillaumet, Franck Suzenet Magnesium in methanol was found to be an effective and inexpensive reagent for the dehalogenation of (hetero)aryl chlorides, bromides and iodides under mild conditions. The halogen/hydrogen exchange proceeded at room temperature and tolerated functional groups such as esters, nitriles, alcohols, and alkenes.Graphical abstractGraphical abstract for this article
       
  • [1,2,5]Oxadiazolo[3,4-d]pyridazine 1,5,6-trioxides: efficient synthesis
           via the reaction of 3,4-bis(hydroxyimino)methyl)-1,2,5-oxadiazole 2-oxides
           with a mixture of concentrated nitric and trifluoroacetic acids and
           structural characterization
    • Abstract: Publication date: Available online 4 July 2018Source: Tetrahedron LettersAuthor(s): Vladimir A. Ogurtsov, Pavel V. Dorovatovskii, Yan V. Zubavichus, Victor N. Khrustalev, Artem N. Fakhrutdinov, Sergei G. Zlotin, Oleg A. Rakitin An efficient synthesis of [1,2,5]oxadiazolo[3,4-d]pyridazine 1,5,6-trioxides (1) from 3,4-bis(hydroxyimino)methyl)-1,2,5-oxadiazole 2-oxides using a mixture of concentrated nitric and trifluoroacetic acids has been developed. The scope of the unconventional reaction was established. The 4,7-dinitro[1,2,5]oxadiazolo[3,4-d]pyridazine 1,5,6-trioxide 1f represents a new high energy compound, unfortunately with low thermal stability. The parent [1,2,5]oxadiazolo[3,4-d]pyridazine 1,5,6-trioxide 1c was studied by single-crystal X-ray diffraction analysis which revealed a planar molecule with an unusually long intracyclic NN bond of 1.668(5) Å and unexpected exo-cyclic bond angles at the nitroxyl nitrogen atoms. In the crystal, the molecules of 1c are bound to each other by strong π-π stacking and CH⋯O hydrogen bonding interactions into a three-dimensional framework that results in a high crystal density of 1.833 gcm−3.Graphical abstractGraphical abstract for this article
       
  • Palladium-catalyzed C-H formylation of electron-rich heteroarenes through
           radical dichloromethylation
    • Abstract: Publication date: Available online 4 July 2018Source: Tetrahedron LettersAuthor(s): Yan Bao, Jian-Yong Wang, Ya-Xuan Zhang, Yan Li, Xi-Sheng Wang A novel palladium-catalyzed C-H formylation of electron-rich N-, O-, and S-containing heteroarenes has been developed. The key to success is that the commercially available BrCHCl2 was used as a stoichiometric carbonyl source. Mechanistic investigations indicated that different from the known Reimer-Tiemann reaction, this net C-H formylation proceeded through an electrophilc radical-type path.Graphical abstractGraphical abstract for this article
       
  • Direct synthesis of N-arylamides via the coupling of aryl diazonium
           tetrafluoroborates and nitriles under transition-metal-free conditions
    • Abstract: Publication date: Available online 4 July 2018Source: Tetrahedron LettersAuthor(s): Biquan Xiong, Gang Wang, Tao Xiong, Liming Wan, Congshan Zhou, Yu Liu, Panliang Zhang, Changan Yang, Kewen Tang The direct synthesis of N-arylamides via the coupling of aryl diazonium tetrafluoroborates and nitriles under transition-metal-free conditions has been developed. The reported protocol is practical and represents an efficient method to produce functionalized amides in moderate to good yields.Graphical abstractGraphical abstract for this article
       
  • An improved Pfitzinger reaction for the direct synthesis of
           quinoline-4-carboxylic esters/acids mediated by TMSCl
    • Abstract: Publication date: Available online 3 July 2018Source: Tetrahedron LettersAuthor(s): Pan Zhou, Biao Hu, Siyuan Zhao, Qiaohe Zhang, Yanqin Wang, Xiang Li, Fuchao Yu An efficient and facile synthesis of quinoline-4-carboxylic esters/acids by TMSCl-promoted reaction of easily available N,N-dimethylenaminones and isatins in alcohols/water has been developed. The improved Pfitzinger reaction involves esterification and cyclization in one-step process, and in situ formed a carboxylic ester/acid group (CO2R or COOH) at the 4-position of quinoline ring. Moreover, the key features of this protocol are readily available starting materials, good functional group tolerance, mild reaction conditions, operational simplicity, and feasibility of scale up.Graphical abstractAn improved Pfitzinger reaction for the synthesis of quinoline-4-carboxylic esters/acids promoted by TMSCl through esterification and cyclization in one-step cascade process under mild conditions has been developed.Graphical abstract for this article
       
  • Highly diastereo- and enantioselective construction of phthalide-oxindole
           hybrids bearing vicinal quaternary chiral centers via an organocatalytic
           allylic alkylation
    • Abstract: Publication date: Available online 3 July 2018Source: Tetrahedron LettersAuthor(s): Wei Liu, Zhi-Peng Hu, Yan Yan, Wei-Wei Liao A diastereo- and enantioselective synthesis of phthalide-oxindole hybrids including congested adjacent quaternary chiral centers was demonstrated through a Lewis base catalyzed asymmetric allylic alkylation reaction of Morita–Baylis–Hillman carbonates of isatins and 3-cyanophthalides. The various hybrid molecules with two valuable pharmacophores-combined frameworks can be obtained in good to high diastereo- and enantioselectivities.Graphical abstractGraphical abstract for this article
       
  • Stability of twisted diarylnitroxides: Photochemical tests
    • Abstract: Publication date: Available online 3 July 2018Source: Tetrahedron LettersAuthor(s): Alexey Bogdanov, Oleg Levitskiy, Andrey Vorobiev, Tatiana Magdesieva Photochemical stability and possible routes for photodegradation of twisted diarylnitroxides were determined. It was shown that quantum yields for twisted diarylnitroxides fall in the range typical for the best representatives of alkylnitroxides providing an additional support that twisting of the phenyl ring from the N-O conjugation plane constitutes an efficient route for increasing thermo and photo stability of the nitroxides.Graphical abstractGraphical abstract for this article
       
  • Synthesis of N-Aryl-hexaoxazadispiroalkanes using Lanthanide
           Catalysts
    • Abstract: Publication date: Available online 3 July 2018Source: Tetrahedron LettersAuthor(s): Nataliya N. Makhmudiyarova, Irina R. Ishmukhametova, Tatyana V. Tyumkina, Askhat G. Ibragimov, Usein M. Dzhemilev An efficient method was developed for the synthesis of N-arylhexaoxazadispiroalkanes by the ring transformation of heptaoxadispiroalkanes with arylamines in the presence of lanthanide salts as catalysts.Graphical abstractGraphical abstract for this article
       
  • Synthesis of unsaturated silyl nitronates via the silylation of
           conjugated nitroalkenes
    • Abstract: Publication date: Available online 3 July 2018Source: Tetrahedron LettersAuthor(s): Elizaveta A. Khotyantseva, Andrey A. Tabolin, Roman A. Novikov, Yulia V. Nelyubina, Sema L. Ioffe A new method for the synthesis of conjugated silyl nitronates from nitroalkenes is described. The procedure has wide substrate scope and is compatible with in situ generation of the substrates from 2-nitroalcohols or 2-chloro-nitroalkanes. A cascade transformation to give 3,4,5,6-tetrahydropyridine N-oxide derivatives was disclosed.Graphical abstractGraphical abstract for this article
       
  • A novel catalytic system poly(1-vinyl-3-dodecylimidazolium tribromide)/TBN
           for the oxidation of sulfides to sulfoxides with air as oxidant
    • Abstract: Publication date: Available online 2 July 2018Source: Tetrahedron LettersAuthor(s): Hua Zhang, Linlin Qi A novel and recoverable polymeric ionic liquid, poly(1-vinyl-3-dodecylimidazolium tribromide) (Poly[VDIM]Br3), was successfully prepared and fully characterized. And a highly efficient metal-free catalytic system Poly[VDIM]Br3/tert-butyl nitrite was developed for the oxidation of sulfides. With air as oxidant, we have successfully achieved 19 kinds of sulfides selectively and efficiently oxidized to corresponding sulfoxides using this catalytic system at room temperature.Graphical abstractGraphical abstract for this article
       
  • An efficient metal catalyst free approach to synthesize 5-(4-(1,2,4,5
           tetrazin-3-yl)benzylamino)-5-oxopentanoic acid
    • Abstract: Publication date: Available online 2 July 2018Source: Tetrahedron LettersAuthor(s): Berhanu Zewde, Olufolasade Atoyebi, Dharmaraj Raghavan Despite the wide use of 1,2,4,5- tetrazines in biomaterials and materials science, currently there does not exist synthetic method(s) that can yield significant amount of 1,2,4,5- tetrazines without the use of potentially toxic metal catalysts. Here, we report a less energy intensive and more efficient metal catalyst free approach for the synthesis of an asymmetric tetrazine. A range of operating parameters such as extraction pH and temperature were regulated to achieve a practical yield nearly 1.5 times greater than the yields reported in the literature for similar synthetic procedures.Graphical abstractGraphical abstract for this article
       
  • Preparation of new halogenated diphenyl pyrazine analogs in Escherichia
           coli by a mono-module fungal nonribosomal peptide synthetase from
           Penicillium herquei
    • Abstract: Publication date: Available online 2 July 2018Source: Tetrahedron LettersAuthor(s): Can Yang, Yuanyuan Xu, Kangping Xu, Guishan Tan, Xia Yu Pyrazines are important structures widely found in many known drugs. The biological approaches for their synthesis were poorly applied. Herein, microbial production of several halogenated diphenyl pyrazines is reported. These compounds are accumulated via feeding corresponding precursor analogs to Escherichia coli expressing a fungal non-ribosomal peptide synthetase HqlA. Substrate specificity of HqlA was also determined by comparing substrate incorporation efficiencies. HqlA requires a C4-hydroxyl in the substrate and can tolerate certain degrees of size change on the substitution at the carbon next to the hydroxyl group.Graphical abstractGraphical abstract for this article
       
  • Covalently linked dimer of chlorophyll-a derivative with an amide bond and
           its folded conformer
    • Abstract: Publication date: Available online 2 July 2018Source: Tetrahedron LettersAuthor(s): Hitoshi Tamiaki, Tomohiro Tatebe, Yuichi Kitagawa A chlorophyll-a derivative homo-dimer covalently linked with a flexible methylene-amino-methylene group at the 3-position was benzoylated to give the dyad bearing a CH2N(COPh)CH2 linker. The synthetic dyad with the relatively rigid spacer showed red-shifted visible absorption bands and was oxidized more readily, in comparison with the corresponding monomer. The optical and electrochemical properties of the dimer are ascribable to the partial π-stacking of chlorin moieties in the benzoylated dyad, mimicking the special dimeric species in reaction centers of photochemical systems in natural phototrophs.Graphical abstractGraphical abstract for this article
       
  • H+bond+functionalizations+of+benzoyl+acetonitriles/methylsulfones+with+cyclic+2-diazo-1,3-dicarbonyl+compounds:+An+efficient+access+to+diversely+functionalized+naphtho[1,8-bc]pyrans&rft.title=Tetrahedron+Letters&rft.issn=0040-4039&rft.date=&rft.volume=">Cascade CH bond functionalizations of benzoyl acetonitriles/methylsulfones
           with cyclic 2-diazo-1,3-dicarbonyl compounds: An efficient access to
           diversely functionalized naphtho[1,8-bc]pyrans
    • Abstract: Publication date: Available online 2 July 2018Source: Tetrahedron LettersAuthor(s): Beibei Zhang, Bin Li, Chenhao Guo, Xinying Zhang, Xuesen Fan In this paper, a Rh(III)-catalyzed cascade reaction of benzoyl acetonitriles/methylsulfones (1) with cyclic 2-diazo-1,3-dicarbonyl compounds (2) leading to a convenient and efficient preparation of diversely functionalized naphtho[1,8-bc]pyrans is presented. Mechanistically, the formation of the title compounds involves a cascade process including: 1) C(sp2)H/C(sp3)H bonds cleavage, metalation and carbeniod insertion of 1 with 2 followed by an intramolecular annulation to afford substituted 1-naphthol as a key intermediate; 2) C(sp2)H/OH bonds cleavage, metalation and carbeniod insertion of the in situ formed 1-naphthol intermediate with 2 followed by an intramolecular cyclization to give the naphtho[1,8-bc]pyran product. Compared with literature methods for the synthesis of naphtho[1,8-bc]pyran derivatives, this new protocol has advantages such as simple operational procedure, easily obtainable substrates, high efficiency and excellent atom-economy.Graphical abstractGraphical abstract for this article
       
  • Transition-metal-free phenylselenylation of arenes with triflic anhydride
           activated methyl phenyl selenoxide
    • Abstract: Publication date: Available online 2 July 2018Source: Tetrahedron LettersAuthor(s): Yuyao Shi, Pingfan LiGraphical abstractPhenylselenylation of arenes were achieved in a one-pot procedure by treating arene substrates with triflic anhydride activated methyl phenyl selenoxide, and then demethylation with diisopropylamine. This reaction provide a convenient method to prepare diarylselenide products under transition-metal-free conditions.Graphical abstract for this article
       
  • Synthesis of puleganic amides via a catalytically efficient two-step
           approach
    • Abstract: Publication date: Available online 30 June 2018Source: Tetrahedron LettersAuthor(s): Ignacio Pérez, José Gustavo Ávila-Zárraga Puleganic amides display interesting insect-repellent properties. A new synthetic route to this type of amide was developed involving an organocatalytic cyclization and metal-catalyzed hydrogenation in a one-pot protocol. An eco-friendly oxidative amination provided the puleganic amides with only one purification step and acceptable yields.Graphical abstractGraphical abstract for this article
       
  • Chalcone and cinnamate synthesis via one-pot enol silane
           formation-Mukaiyama aldol reactions of ketones and acetate esters
    • Abstract: Publication date: Available online 30 June 2018Source: Tetrahedron LettersAuthor(s): C. Wade Downey, Hadleigh M. Glist, Anna Takashima, Samuel R. Bottum, Grant J. Dixon Aryl alkyl ketones, acetate esters, and acetamides undergo facile one-pot enol silane formation, Mukaiyama aldol addition, and dehydrosilyloxylation in the presence of an amine base and excess trimethylsilyl trifluoromethanesulfonate. The chalcone and cinnamate products are generally recovered in high yield. The relative stoichiometry of the trimethylsilyl trifluoromethanesulfonate and amine base reagents determines whether the reaction yields the β-silyloxy carbonyl product or the α,β-unsaturated carbonyl.Graphical abstractGraphical abstract for this article
       
  • Stereoselective synthesis of spiro[pyrrolidin-3,3′-oxindoles] via
           organocatalyzed asymmetric Mannich-type reaction
    • Abstract: Publication date: Available online 30 June 2018Source: Tetrahedron LettersAuthor(s): Hui Shao, Xiu-Wu Huang, Lei Song, Wen-Ting Zhou, Guan-Ping Tang, Long Ye The organocatalyzed asymmetric Mannich-type spirocyclization was employed to access the spiro[pyrrolidin-3,3′-oxindoles], a biologically privileged ring structure, from readily available 2-oxotryptaphan methyl ester and aromatic aldehydes. The stereoselectivity of this cyclization are closely correlated with the organocatalyst and solvent used for the reaction. The best diastereoselectivity (d.r. ≥99%) was achieved using only 5% loading of the bifunctional organocatalyst, Takemoto’s thiourea, and dioxane as solvent, resulting in the formation of the the spirocycle with the (2′R, 3R) configuration. The yield could be increased up to 97% when excess of benzaldehyde was used to overcome its trimerization.Graphical abstractGraphical abstract for this article
       
  • Cu catalyzed cross-dehydrogenative coupling reaction for the synthesis of
           3-hydroxy-2-pyrrolidinones
    • Abstract: Publication date: Available online 30 June 2018Source: Tetrahedron LettersAuthor(s): Rajib Sarkar, Chhanda Mukhopadhyay A new convenient strategy for the synthesis of 3-hydroxy-2-pyrrolidinone derivatives featuring regioselective CC coupling has been developed. This is a Cu (II) catalyzed cross dehydrogenative coupling (CDC) involving enamino-ketones of benzyl amines and di-alkyl acetylenedicarboxylate, followed by cyclization by primary amines. TBHP (tert-butyl hydroperoxide) has been used as the oxidant to promote the coupling protocol. This synthetic route principally demonstrates the scope of CDC reaction and also applicable to gram-scale synthesis.Graphical abstractGraphical abstract for this article
       
  • Recent advances in Garratt-Braverman cyclization: Mechanistic and
           synthetic explorations
    • Abstract: Publication date: Available online 28 June 2018Source: Tetrahedron LettersAuthor(s): Prabuddha Bhattacharya, Monisha Singha, Eshani Das, Arundhoti Mandal, Manasi Maji, Amit Basak Garratt-Braverman cyclization has emerged as one of the simplest synthetic tool to construct two consecutive CC bonds leading to the formation of various important structural scaffolds having significance in the field of therapeutics and material science. The strategic design of suitable precursor for this cycloaromatization reaction involves the deep understanding of reaction pathways involving diradicals and ions. On the other hand, the reaction offers an unprecedented mechanistic paradox for the chemists to solve. This report aims at outlining the recent mechanistic and synthetic developments with special emphasis on the research outcomes from our laboratory.Graphical abstractGraphical abstract for this article
       
  • Synthetic application of water-soluble hypervalent iodine reagents in
           aqueous media
    • Abstract: Publication date: Available online 26 June 2018Source: Tetrahedron LettersAuthor(s): Yong-Chao Han, Chi Zhang Along with the vigorous development of hypervalent iodine chemistry, water-soluble hypervalent iodine reagents have received considerable attentions in recent years. In order to obtain water-soluble hypervalent iodine reagents, two strategies have been employed including introduction of hydrophilic functional groups onto the phenyl ring and formation of complex of iodosylbenzene with crown ether. And, it is observed that four kinds of hypervalent iodine reagents exhibit more or less solubility in water including hypervalent iodine reagents containing hydrophilic ligands, diaryliodonium salts, oligomeric iodosylbenzene sulfate, and iodylbenzene and its derivatives. In this review, we summarize these water-soluble hypervalent iodine reagents and their broad synthetic applications in aqueous media.Graphical abstractGraphical abstract for this article
       
  • Azaphilone and Isocoumarin Derivatives from the Sponge-Derived Fungus
           Eupenicillium sp. 6A-9
    • Abstract: Publication date: Available online 25 June 2018Source: Tetrahedron LettersAuthor(s): Bin-Bin Gu, Ying wu, Jie Tang, Wei-hua Jiao, Lei Li, Fan Sun, Shu-Ping Wang, Fan Yang, Hou-Wen Lin Three new azaphilones, eupenicilazaphilones A–C (1–3), and one new isocoumarin, eupenicillin A (4), as well as five known azaphilones were isolated from the sponge-derived fungus Eupenicillium sp. 6A-9. Their structures were elucidated by detailed spectroscopic analysis, comparison with literature data, and 13C NMR chemical shifts and TDDFT/ECD calculations. The antibacterial activity against Staphylococcus aureus ATCC25923, methicillin-resistant Staphylococcus aureus ATCC4330, and Acinetobacter baumanii ATCC19606 as well as the cytotoxic activity towards human cancer lines MCF-7 and A549 were examined.Graphical abstractGraphical abstract for this article
       
  • NH4I/EtOCS2K promoted synthesis of substituted benzils from
           diphenylacetylene derivatives
    • Abstract: Publication date: Available online 22 June 2018Source: Tetrahedron LettersAuthor(s): Shaohua Jiang, Yibiao Li, Xianglin Luo, Guoling Huang, Yan Shao, Dongli Li, Bin Li A facile protocol is described for the synthesis of benzil derivatives from readily accessible diarylacetylene derivatives using the NH4I/EtOCS2K system. This novel protocol results in excellent chemoselectivity and provided good to excellent yields. A control experiment indicated that the reaction proceeds via NH4I promoted EtOCS2K dimerization to give the corresponding dixanthogen and subsequent dixanthogen assisted oxidation.Graphical abstractGraphical abstract for this article
       
  • Access to 3-aminobenzothiophenes and 3-aminothiophenes fused to 5-membered
           heteroaromatic rings through 6π-electrocyclization reaction of
           keteniminium salts
    • Abstract: Publication date: Available online 21 June 2018Source: Tetrahedron LettersAuthor(s): Amandine Kolleth, Simona Müller, Alexandre Lumbroso, Gamze Tanriver, Saron Catak, Sarah Sulzer-Mossé, Alain De Mesmaeker We described a general approach to 3-aminobenzothiophenes and 3-aminothiophenes fused to 5-membered heteroaromatic rings as thiophenes, furans and pyrroles through a 6π-elctrocyclization reaction of keteniminium salts. We investigated various substituents not only on the aromatic rings, but also at C-2 and on the nitrogen atom of the keteniminium salt. In particular, we have determined the electronic requirements of the nitrogen substitution to secure the efficient formation of the corresponding keteniminium salt. A clear relation between the pKa of the amine leading to the formation of the keteniminium salt and the yield obtained for benzothiophene is established and should find broad application to other reactions involving these intermediates. Additional insight on the ease of this 6π-electrocyclization reaction was gained through competition reactions and DFT calculations.Graphical abstractGraphical abstract for this article
       
  • Pd-catalyzed oxidative homo-coupling of acrylates and aromatic alkenes for
           the conjugated diene synthesis
    • Abstract: Publication date: Available online 11 June 2018Source: Tetrahedron LettersAuthor(s): Ting Zhu, Zhen Li, Fanhua Xiao, Wei-Liang Duan We developed a bidentate monoanionic nitrogen ligand that was effective in the Pd-catalyzed oxidative homo-coupling reaction of acrylates and aromatic alkenes. In the presence of Pd(OAc)2/ligand several conjugated dienes were obtained in good yields with high stereoselectivities.Graphical abstractGraphical abstract for this article
       
  • Salvifarinin A, a neo-clerodane diterpenoid with a 6/5/7 tricyclic
           skeleton from Salvia farinacea
    • Abstract: Publication date: Available online 7 June 2018Source: Tetrahedron LettersAuthor(s): Min Fan, Xue-Jiao Chen, Xing-De Wu, Li-Dong Shao, Xu Ji, Qin-Shi Zhao Salvifarinin A (1), a rearrangement product of Languidulane-type clerodane diterpenoids with a 6/5/7 tricyclic ring skeleton fused with γ-lactone ring and furan ring, and two new biogenetically related diterpernoids, salvifarinins B (2) and C (3), were isolated from the aerial parts of Salvia farinacea. The absolute configuration of 1 was elucidated by extensive spectroscopic methods, and confirmed by single crystal X-ray diffraction and bio-inspired semisynthesis. The plausible biogenetic pathway was also proposed. Compound 2 displayed a potent effect on reducing hepatic steatosis.Graphical abstractGraphical abstract for this article
       
  • Violaceimides A–E, sulfur-containing metabolites from a
           sponge-associated fungus Aspergillus violaceus
    • Abstract: Publication date: Available online 30 May 2018Source: Tetrahedron LettersAuthor(s): Jiaoding Yin, Chanjuan Zhang, Jiguo Huang, Jianping Zhang, Dong Liu, Jian Huang, Peter Proksch, Wenhan Lin Five new methylsuccinimide-based sulfur-bearing compounds, namely violaceimides A–E (1–5), were isolated from the sponge-associated fungal strain Aspergillus violaceus WZXY-m64-17. Their structures were determined by analyses of the HRESIMS, 1D and 2D NMR data, along with the Mosher’s and Snatzke’s methods, experimental and calculated ECD data, as well as chemical conversion for the configurational assignment. The structures of 1–5 featured the fusion of methylsuccinimide with a modified cysteine to incorporate sulfur element, which was found from nature for the first time. The biogenetic relationship of the sulfur-containing compounds was postulated. Violaceimides A and B exerted selective inhibition against the growth of human leukemia U937 and human colorectal cancer cell HCT-8 with low cytotoxicity toward Vero cells, whereas violaceimide E showed moderate activity to inhibit U937 cells. The preliminary structure-activity relationship was discussed.Graphical abstractGraphical abstract for this article
       
  • A convenient synthesis of (E)-conjugated polyene sulfonyl derivatives with
           excellent stereospecificity
    • Abstract: Publication date: Available online 24 May 2018Source: Tetrahedron LettersAuthor(s): Chunyan Yu, Zhongwen Lv, Sheng Xu, Jun Zhang A highly selective synthesis of conjugated polyene sulfonyl derivatives is described via the elimination of disulfonyl chloride with readily accessible raw material dihaloalkane. The protocol offers a convenient way to form sulfonamides, sulfonates and even sulfones. Furthermore, this method was manipulated under mild condition with simple operation in high yield to afford only trans products.Graphical abstractGraphical abstract for this article
       
 
 
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