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Tetrahedron
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Published by Elsevier Homepage  [3182 journals]
  • Syntheses of spiro[indazole-3,3′-indolin]-2′-ones and
           spiro[indazole-3,3′-indolin]-2′-imines via 1,3-dipolar cycloadditions
           of arynes and studies on their isomerization reactions
    • Abstract: Publication date: Available online 9 November 2019Source: TetrahedronAuthor(s): Bin Cheng, Yuntong Li, Bing Zu, Taimin Wang, Renqi Wang, Yun Li, Hongbin Zhai A 1,3-dipolar cycloaddition reaction of arynes with 3-diazoindolin-2-ones under mild conditions in excellent yields has been developed, which allows facile access to an library of labile spiro[indazole-3,3′-indolin]-2′-ones. Spiro[indazole-3,3′-indolin]-2′-imines could be obtained as well following the same protocol. The isomerization reaction of spiro[indazole-3,3′-indolin]-2′-ones under thermal or acidic conditions has been efficiently achieved to afford a wide range of indazolo-[2,3-c]quinazolin-6(5H)-ones and the one-pot synthesis of indazolo-[2,3-c]quinazolin-6(5H)-ones from arynes and 3-diazoindolin-2-ones is also described. Whereas, spiro[indazole-3,3′-indolin]-2′-imines could not undergo the same rearrangement.Graphical abstractImage 1
       
  • Syntheses of o-iodobenzyl alcohols‒BODIPY structures as potential
           precursors of bimodal tags for positron emission tomography and optical
           imaging
    • Abstract: Publication date: Available online 8 November 2019Source: TetrahedronAuthor(s): Thifanie Christine, Alexis Tabey, Thomas Cornilleau, Eric Fouquet, Philippe Hermange Aiming the faster development from bench to bedside of new potential tracers, multimodal tracers for positron emission tomography (PET) and optical imaging (OI) have emerged as a very promising tool. Indeed, they combine the simplicity of use of optical techniques for in vitro/in vivo pre-clinical studies with the various clinical possibilities offered by PET imaging using their radioactive versions. In this context, the preparation of new tags detectable by fluorescence imaging and potentially suitable for PET imaging after a last-step 11C-labeling of the corresponding precursor has been investigated. Various designs and syntheses were explored by linking o-iodobenzyl alcohols and tetramethyl-BODIPY moieties together. Among them, the most promising structure was produced in 30% yield over five steps from a commercially available and inexpensive starting material.Graphical abstractImage 1
       
  • Base and catalyst-free synthesis of nitrobenzodiazepines via a cascade
           N-nitroallylation-intramolecular aza-Michael addition involving
           o-phenylenediamines and nitroallylic acetates
    • Abstract: Publication date: Available online 6 November 2019Source: TetrahedronAuthor(s): Divya K. Nair, Sudheesh T. Sivanandan, Pravin Kendrekar, Irishi N.N. Namboothiri A [4+3] annulation of o-phenylenediamines with primary nitroallylic acetates affords nitrobenzodiazepines (NBDZs) in good to excellent yield. The reaction which proceeds in MeOH at room temperature in the absence of any base or catalyst involves a cascade SN2 N-nitroallylation-intramolecular aza-Michael addition sequence. In the case of mono-N-arylated o-phenylenediamines and o-aminobenzamides, the reaction stops at the SN2 stage affording nitroallylic amines. On the other hand, reaction of o-aminobenzamides with secondary nitroallylic acetates delivers SN2′ products. Formation of stable SN2 and SN2′ products provides insights into the reactivity of primary and secondary nitroallylic acetates and also the mechanism of formation of nitrobenzodiazepines.Graphical abstractImage 1
       
  • Hanessian-Hullar reaction in the synthesis of highly substituted
           trans-3,4-dihydroxypyrrolidines: Rhamnulose iminosugar mimics inhibit
           α-glucosidase
    • Abstract: Publication date: Available online 6 November 2019Source: TetrahedronAuthor(s): Zilei Liu, Akihide Yoshihara, Sarah F. Jenkinson, Mark R. Wormald, Ciarán Kelly, John T. Heap, Mikkel H.S. Marqvorsen, Ramón J. Estévez, George W.J. Fleet, Shinpei Nakagawa, Ken Izumori, Robert J. Nash, Atsushi Kato The key step in the syntheses of highly substituted trans-3,4-dihydroxypyrrolidines is introduction of bromide by stereospecific and regiospecific Hanessian-Hullar reactions; benzylidene lactones of l-rhamnonolactone and 6-deoxy-l-gulonolactone allow introduction of N at C2 with inversion or retention of configuration. Initially a protecting group, the benzylidene acetal then provides a bromide at C5 to allow formation of the pyrrolidine ring. With silyl protecting groups, bromide was introduced at C5 with inversion of configuration whereas benzoyl protection gave a mixture of retention and inversion, indicative of neighbouring group participation in a Hanessian-Hullar reaction. Four stereoisomeric pyrrolidines - iminosugar mimics of α- and β-l-rhamnulose and α- and β-6-deoxy-d-sorbose were prepared. Only the α-l-rhamnulose mimic showed moderate inhibition of rhamnosidase but some were good inhibitors of α-glucosidases; none inhibited rhamnose isomerase and they had a small effect as synthetic inducers of the rhamnose catabolic operon in E. coli.Graphical abstractImage 1
       
  • A near-infrared large Stokes shift probe based enhanced ICT strategy for
           F- detection in real samples and cell imaging
    • Abstract: Publication date: Available online 6 November 2019Source: TetrahedronAuthor(s): Qinghua Hu, Qiuxiang Huang, Yu Mao, Xinlin Liu, Fangrong Tan, Yuyuan Wang, Qiang Yin, Xumeng Wu, Hongqing Wang In view of the few reports of the near-infrared emissive probe for fluorine ions, we herein designed and synthesized a new easy-to-get colorimetric and near-infrared emissive fluorescent probe (IS-NR-F) with a large Stokes shift (>127 nm). Based on specific F− triggered desilylation reaction induced enhanced ICT strategy involving the donor phenolate anion and the acceptor malononitrile, the probe exhibited dual colorimetric and fluorescent turn-on responses, and provided excellent selectivity for fluoride ions. The fluorescent response at 665 nm displayed very good linear relationship in the wide concentration range and deduced a low detection limit of 0.09 ppm. The detection mechanism was confirmed by 1H NMR, ESI-MS, and TLC calculation. Moreover, probe IS-NR-F has been successfully employed to detect F− in tap water, toothpaste samples, and fluorescent imaging of F− in HeLa cells.Graphical abstractImage 1
       
  • An expeditious entry to rare
           tetrahydroimidazo[1,5-c]pyrrolo[1,2-a]pyrimidin-7(8H)-ones: A single-step
           gateway synthesis of glochidine congeners
    • Abstract: Publication date: Available online 5 November 2019Source: TetrahedronAuthor(s): Jeong Moo Seo, Ahmed H.E. Hassan, Yong Sup Lee A single-step gateway synthesis of glochidine and its congeners that possess the rare uncommon tetrahydroimidazo[1,5-c]pyrrolo[1,2-a]pyrimidine core was developed employing histamine and readily available γ-ketoesters. Key features of the developed reaction involve tandem three C–N bonds formation and concomitant annulation of two rings in one pot to access this unique and complex tricyclic structure. Exploration of the unknown bioactivity of these compounds revealed that they elicit antiproliferative activity comparable to the anticancer drug imatinib against 6 cancer cell lines.Graphical abstractImage 1
       
  • Increasing the antioxidant capability via the synergistic effect of
           coupling diphenylamine with sterically hindered phenol
    • Abstract: Publication date: Available online 5 November 2019Source: TetrahedronAuthor(s): Clare L. Higgins, Sorin V. Filip, Ashfaq Afsar, Wayne Hayes A series of novel diphenylamine-phenol antioxidants were synthesised that combined the two antioxidant types into a single molecule. These antioxidants were then functionalised with alkyl chains to aid their solubility in hydrocarbon media. As part of a structure-activity study, diphenylamine derivatives were also generated bearing carboxylic acid functionalities in either the ortho, meta or para position with respect to the secondary amine. Methyl or ethyl spacers were also incorporated between the carboxylic acid and the aromatic ring. The antioxidant ability of the diphenylamine-phenols was evaluated using Differential Scanning Calorimetry (DSC) and compared to commercially available antioxidants Irganox L135 and Irganox L57 both as individual components and when blended together. The diphenylamine-phenol antioxidant with an ethyl spacer between the diphenylamine and carboxylic acid in the meta position with respect to the secondary amine functionality showed an impressive oxidation induction time of ca. 24 min in direct comparison with the blend of Irganox L135 and Irganox L57 (ca. 16 min).Graphical abstractImage 1
       
  • Visible-light-mediated selective thiocyanation/ipso-cyclization/oxidation
           cascade for the synthesis of thiocyanato-containing azaspirotrienediones
    • Abstract: Publication date: Available online 5 November 2019Source: TetrahedronAuthor(s): Yuan Chen, Yu-Jue Chen, Zhi Guan, Yan-Hong He A visible-light-mediated metal-free thiocyanate radical addition/ipso-cyclization/oxidation cascade reaction for the synthesis of thiocyanato-containing azaspirotrienediones from N-phenylpropynamides is described. Cheap and readily available ammonium thiocyanate was used as a precursor to the thiocyanate free radical, which undergoes a radical addition reaction with the alkyne, followed by selective ipso-cyclization and oxidation to afford the dearomatized products. No product of ortho-cyclization was detected. The reaction completes the synthesis of C–S, C–C, and C=O bonds in one pot, with abundant and renewable air oxygen as the sole sacrificial reagent and oxygen source.Graphical abstractA visible-light-mediated metal-free thiocyanate radical addition/ipso-cyclization/oxidation cascade reaction for the synthesis of thiocyanato-containing azaspirotrienediones from N-phenylpropynamides is described.Image 1
       
  • Squarate desymmetrisation–ozonolysis as an approach to
           β-substituted-α-ketosuccinates and squalestatin synthesis
    • Abstract: Publication date: Available online 5 November 2019Source: TetrahedronAuthor(s): Herman O. Sintim, Anne Valade, David C. Harling, David M. Hodgson Silylated tertiary alcohols from 1,2-addition of alkyllithiums to dialkyl squarates undergo alkene ozonolysis to give β-substituted-α-keto-β-(silyloxy)succinates. With 3-(triethylsilyloxy)butyllithium the methodology was applied to the 2,8-dioxabicyclo[3.2.1]octane core of the squalestatins. Enantioselective 1,2-addition to di-tert-butyl squarate using butyllithium or diethylzinc/Ti(iPrO)4 in the presence of chiral ligands (such as bisoxazolines or camphorsulfonamides, respectively) gave the corresponding tertiary alcohols in up to 67.5:32.5 er.Graphical abstractImage 1
       
  • Charge-enhanced thiourea catalysts as hydrogen bond donors for
           Friedel‒Crafts Alkylations
    • Abstract: Publication date: Available online 2 November 2019Source: TetrahedronAuthor(s): Ivor Smajlagic, Brenden Carlson, Nicholas Rosano, Hayden Foy, Travis Dudding Charge-enhanced catalysis has emerged as a powerful alternative to the mainstream use of neutral catalysis.With this in mind, we report a catalytic Friedel‒Crafts alkylation method catalyzed by a charged thiourea incorporating a cationic cyclopropenium moiety. Mechanistic studies, including density functional theory computational calculations, variable time normalization analysis, and 1H NMR binding studies, collectively reveal this charged-enhanced reactivity proceeds by a dual hydrogen bond-mediated LUMO-lowering mode of substrate activation. Key to these findings is the observed steady-state concentration of the catalyst with in situ derived monomeric catalytic species predominating under the reaction conditions.Graphical abstractImage 1
       
  • Graphical abstract TOC
    • Abstract: Publication date: 22 November 2019Source: Tetrahedron, Volume 75, Issue 47Author(s):
       
  • Graphical abstract TOC
    • Abstract: Publication date: 22 November 2019Source: Tetrahedron, Volume 75, Issue 47Author(s):
       
  • Phosphinoyl radical-initiated vicinal hydroxy-phosphorylation of alkenes
    • Abstract: Publication date: 22 November 2019Source: Tetrahedron, Volume 75, Issue 47Author(s): Adedamola Shoberu, Shuai-Shuai Li, Guo-Yu Zhang, Da-Peng Li, Jian-Ping Zou A protocol of Mn(OAc)3–mediated α,β-hydroxy-phosphorylation of alkenes with phosphorus-centered radicals generated from diphenylphosphine oxide is described. A combination of steric and electronic factors played an important role in this reaction. The reactions of styrenes bearing ortho-substituent gave the selective β-hydroxyphosphine oxide products.Graphical abstractImage 1
       
  • Unique chemoselective Mukaiyama aldol reaction of silyl enol diazoacetate
           with aldehydes and acetals catalyzed by MgI2 etherate
    • Abstract: Publication date: 22 November 2019Source: Tetrahedron, Volume 75, Issue 47Author(s): Xiangwei Meng, Haokun Pan, Tengjiang Zhong, Xingxian Zhang Functionalized diazo acetoacetates are prepared by an efficient Mukaiyama aldol reaction between 3-TBSO-2-diazo-3-butenoate with aldehydes and acetals under mild reaction conditions. A variety of substituted aldehydes and the corresponding acetals are both accessible in good to excellent yields through this methodology. MgI2 etherate (MgI2·(OEt2)n) is the preferred catalyst and, the addition proceeds without decomposition of the diazo moiety. In addition, this MgI2·(OEt2)n-catalyzed Mukaiyama aldol reaction shows unique chemoselectivity towards aldehydes and acetals.Graphical abstractImage 1
       
  • Convenient synthesis of 2-(het)arylpyrrolidines via stable 1-pyrrolinium
           salts
    • Abstract: Publication date: 22 November 2019Source: Tetrahedron, Volume 75, Issue 47Author(s): Anna S. Melyashova, Andrey V. Smolobochkin, Almir S. Gazizov, Julia K. Voronina, Alexander R. Burilov, Michail A. Pudovik The efficient method for the synthesis of 2-(het)aryl-substituted pyrrolidines possessing exocyclic carbon-carbon double bond via the Mannich-type reaction of stable 3-arylidene-1-pyrrolinium salts with different heterocyclic C-nucleophiles is proposed.Graphical abstractImage 1
       
  • Synthesis and properties of perfluoroalkylated TIPS-pentacenes
    • Abstract: Publication date: 22 November 2019Source: Tetrahedron, Volume 75, Issue 47Author(s): Tomohiro Agou, Seima Suzuki, Yasunori Kanno, Takaaki Hosoya, Hiroki Fukumoto, Yoshiyuki Mizuhata, Norihiro Tokitoh, Yuki Suda, Shunsuke Furukawa, Masaichi Saito, Toshio Kubota The introduction of perfluoroalkyl (Rf) groups into polycyclic aromatic hydrocarbons (PAHs) is a potential strategy for developing air-stable electron-acceptors that are useful for manufacturing novel n-type organic semiconductors. This paper describes a facile synthetic method for 9,13-bis[(triisopropylsilyl)ethynyl]pentacene (“TIPS-pentacene”) derivatives bearing two or four Rf groups at peripheral regions. The molecular structures of newly synthesized TIPS pentacenes bearing four Rf groups were established by single-crystal X-ray analysis. The Rf-substituted TIPS-pentacenes are stable both in solutions and in the solid state under ambient conditions, probably because of the combination of the TIPS-ethynyl and Rf groups. The Rf groups stabilize the π-orbitals of the TIPS-pentacene framework and improve the electron-accepting properties, as evidenced by electrochemical measurements and photoelectron yield spectroscopy (PYS).Graphical abstractImage 1
       
  • Reactions of 3-R-5-nitropyridines with nucleophiles: Nucleophilic
           substitution vs conjugate addition
    • Abstract: Publication date: 22 November 2019Source: Tetrahedron, Volume 75, Issue 47Author(s): Maxim A. Bastrakov, Vladislav V. Nikol’skiy, Alexey M. Starosotnikov, Ivan V. Fedyanin, Svyatoslav A. Shevelev, Daniil A. Knyazev A number of 3-R-5-nitropyridines were synthesized and their reactions with various types of nucleophiles were investigated. The reaction outcome depends on the nature of a nucleophile: in case of anionic O-, N- and S-nucleophiles the previously unreported substitution of non-activated nitro group occurred while carbon nucleophiles underwent dearomatization of the pyridine ring with the formation of products of 1,2- and 1,4-addition.Graphical abstractImage 1
       
  • Ligand-controlled phosphine-free Co(II)-catalysed cross-coupling of
           secondary and primary alcohols
    • Abstract: Publication date: 22 November 2019Source: Tetrahedron, Volume 75, Issue 47Author(s): Shi-Qi Zhang, Bin Guo, Ze Xu, Hong-Xi Li, Hai-Yan Li, Jian-Ping Lang Cobalt(II) complexes (5 mol% Co) bearing phosphine-free N˄N˄N pincer ligands efficiently catalyze C–C coupling of secondary and primary alcohols to selectively form α-alkylated ketones with a good functional group compatibility using NaOH (20 mol%) as a base at 120 °C. The NH group on the N˄N˄N–Co(II) precatalyst controls the activity and selectivity. This simple catalytic system is involved in the synthesis of quinolones via the dehydrogenative annulation of 2-aminobenzyl alcohols with secondary alcohols.Graphical abstractImage 1
       
  • Hydrochlorofluoromethylation of unactivated alkenes with
           chlorofluoroacetic acid
    • Abstract: Publication date: 22 November 2019Source: Tetrahedron, Volume 75, Issue 47Author(s): Claudio F. Meyer, Sandrine M. Hell, Jeroen B.I. Sap, Antonio Misale, Aldo Peschiulli, Daniel Oehlrich, Andrés A. Trabanco, Véronique Gouverneur An operationally simple method enabling hydrochlorofluoromethylation of unactivated alkenes under visible light activation is reported. The procedure has various benefits. It uses commercially available and inexpensive chlorofluoroacetic acid and phenyliodine(III) diacetate for the generation of the required chlorofluoromethyl radical, it converts feedstock olefins into attractive 1-chloro-1-fluoroalkanes, and it tolerates a broad variety of functional groups. The chlorofluoromethyl radical has a reactivity profile towards alkenes similar to the nucleophilic difluoromethyl radical.Graphical abstractImage 1
       
  • Diversity-Oriented Synthesis of Bioactive Azaspirocycles
    • Abstract: Publication date: 22 November 2019Source: Tetrahedron, Volume 75, Issue 47Author(s): Lance T. Lepovitz, Stephen F. Martin A collection of novel azaspirocyclic β-arylethylamines was prepared in good yield and excellent diastereoselectivity by an expedient strategy that features condensation of a cyclic ketone with an amino allylsilane and a tandem aza-Sakurai cyclization to generate several different spirocyclic N-heterocycles. Subsequent elaboration of the spirocyclic scaffold was achieved via Pictet-Spengler cyclizations, Suzuki cross-coupling reactions, N-functionalizations, and olefin refunctionalization reactions to create a diverse library of compounds, several of which have nanomolar affinity for the sigma 1 receptor and transmembrane protein 97 (TMEM97).Graphical abstractImage 1
       
  • Graphical abstract TOC Cont'd
    • Abstract: Publication date: 22 November 2019Source: Tetrahedron, Volume 75, Issue 47Author(s):
       
  • Synthesis of non-natural cyanthiwigin–gagunin hybrids through late-stage
           diversification of the cyanthiwigin natural product core
    • Abstract: Publication date: Available online 1 November 2019Source: TetrahedronAuthor(s): Kelly E. Kim, Yuka Sakazaki, Brian M. Stoltz Derivitization of natural product scaffolds produces diversely functionalized molecules for biological study and offers insight into the reactivities of complex molecular architectures. In the present study, the tricyclic framework of the cyanthiwigin natural product family was employed as a platform for late-stage diversification. The design and synthesis of several non-natural “hybrid” molecules resembling both the cyanthiwigin and gagunin natural products was accomplished, and the results of these investigations are described herein.Graphical abstractImage 1
       
  • I2-promoted tandem cyclization to synthesize polysubstituted
           pyrano[3,2-c]chromene-2,5-diones
    • Abstract: Publication date: Available online 1 November 2019Source: TetrahedronAuthor(s): Qun Cai, Shiyi Zhuang, Mian Yang, Na Peng, Yi Liu, Anxin Wu An efficient and convenient method for the synthesis of various substituted pyrano[3,2-c]chromene-2,5-diones was developed via the I2-promoted tandem cyclization of commercially available aryl methyl ketones and 4-hydroxycoumarins. Preliminary mechanism studies indicated that the reaction involved a consecutive iodination/Kornblum oxidation/annulation process. HI produced in the I2-DMSO system acted as an important promoter, accelerating the annulation protocol.Graphical abstractImage 1
       
  • Structural and synthetic studies on maleic anhydride and related diacid
           natural products
    • Abstract: Publication date: Available online 31 October 2019Source: TetrahedronAuthor(s): David M. Heard, Emyr R. Tayler, Russell J. Cox, Thomas J. Simpson, Christine L. Willis A concise approach has been developed for the total syntheses of tricladic acids A, B and C previously isolated from Tricladium castaneicola confirming the structures of these fungal natural products. The required (E)-1,3-diene scaffolds were generated with complete stereocontrol via coupling of the appropriate nitronate with an unsaturated bromo-diester which was prepared in 2 steps from citraconic anhydride. The reported structures of the anhydride waquafranone B and the parent diacid were synthesised leading to revision of the originally proposed structure of the natural product and, in accord with Sutherland, confirming that anhydrides with exo-dienes are unstable. Biomimetic dimerisations of the proposed monomers of the nonadride scytalidin were investigated.Graphical abstractImage 1
       
  • High diastereoselective synthesis of spiro-barbituratechromans via domino
           oxa-Michael/1,6-addition reactions of ortho-hydroxyphenylsubstituted
           para-quinone methides with barbiturate-based olefins
    • Abstract: Publication date: Available online 31 October 2019Source: TetrahedronAuthor(s): Mingming Huo, Jing Zhou, Lijuan Bai, Qigui Xu, Zhihong Zhou, Hui Zhou, Guojuan Liang A novel Et3N-catalyzed domino oxa-Michael/1,6-addition reaction of ortho-hydroxyphenylsubstituted p-QMs with barbiturate-based olefins is achieved under mild conditions. Various new spiro-barbituratechromans were obtained in excellent yields and diastereoselectivities (90–99% yield,>99:1 dr). The structure of the new compound 3a was determined by single crystal X-ray analysis.Graphical abstractImage 1
       
  • Novel pyrrolo[2,3-d]pyrimidine derivatives: Design, synthesis, structure
           elucidation and in vitro anti-BVDV activity
    • Abstract: Publication date: Available online 31 October 2019Source: TetrahedronAuthor(s): Farid M. Sroor, Wahid M. Basyouni, Wael M. Tohamy, Tawfeek H. Abdelhafez, Mostafa K. El-awady The progression of drug resistance of viral infection justifies the discovering of new anti-viral agents. Thus, a novel series of pyrrolopyrimidine derivatives 5–7 and 9–18 were designed, synthesized and fully characterized by IR, mass spectroscopy, NMR, and elemental analysis. The structure of 4,6-dichloro-pyrrolo[2,3-d]pyrimidine 10 elucidated by single crystal X-ray diffraction. Herein, we reported the first pyrrolo[2,3-d]pyrimidine compounds with trichloromethane at position 2 of the pyrimidine ring. As initial biological activity screening, evaluation of the pyrrolo[2,3-d]pyrimidine compounds as anti-BVDV (Bovine Viral Diarrhea Virus) was examined. The compounds 11, 13, 16 and 17 exhibited excellent activity as a potent inhibitor against BVDV. Structure activity relationship showed that the pyrrolo[2,3-d]pyrimidine molecules presenting hydrogen atom or trichloromethyl group on C2 and chlorine, sulfur, pyrrolidine or methoxy groups on C4 of the pyrimidine ring showed high activity as anti-BVDV in comparison with the compounds which have Cl or CH3 on C2 position.Graphical abstractImage 1
       
  • Bismuth-catalyzed methylation and alkylation of quinone derivatives with
           tert-butyl peroxybenzoate as an oxidant
    • Abstract: Publication date: Available online 31 October 2019Source: TetrahedronAuthor(s): Jian Yang, Yu Dong, Shuai He, Zhi-Chuan Shi, Yu Wang, Ji-Yu Wang A bismuth-catalyzed methylation of quinones in the presence of tert-butyl peroxybenzoate (TBPB) was developed via a radical reaction mechanism. Particularly, TBPB was used not only as an efficient oxidant, but also as a green methyl source in such transformation. Moreover, this method could also be efficiently extended to the alkylation of quinones. This reaction tolerated a series of functional groups and prepared a series of derivatives of vitamin K3 and benzoquinone. Notably, antimalarial parvaquone was synthesized by the reaction.Graphical abstractImage 1
       
  • Visible-light photoredox catalyzed synthesis of polysubstituted furfuryl
           trifluoroacetamide derivatives
    • Abstract: Publication date: Available online 30 October 2019Source: TetrahedronAuthor(s): Taotao Chen, Wei Wu, Zhiqiang Weng A visible-light photoredox catalyzed reaction of enynones with 2,2,2-trifluoroacetamide to access polysubstituted furfuryl trifluoroacetamide derivatives under mild reaction conditions is reported. This transformation proceeds through the furan-substituted carbene intermediate, which subsequently undergoes an intermocular trapping process by 2,2,2-trifluoroacetamide to produce the desired furfuryl trifluoroacetamides.Graphical abstractImage 1
       
  • Air-stable binuclear Titanium(IV) salophen perfluorobutanesulfonate with
           zinc power catalytic system and its application to C–S and C–Se bond
           formation
    • Abstract: Publication date: Available online 30 October 2019Source: TetrahedronAuthor(s): Lingxiao Wang, Jie Qiao, Jiancong Wei, Zhiwu Liang, Xinhua Xu, Ningbo Li An air-stable μ-oxo-bridged binuclear Lewis acid of titanium(IV) salophen perfluorooctanesulfonate [{Ti(salophen)H2O}2O][OSO2C4F9]2 (1) was successfully synthesized by the reaction of TiIV(salophen)Cl2 with AgOSO2C4F9 and characterized by techniques such as IR, NMR and HRMS. This complex was stable open to air over a year, and exhibited good thermal stability and high solubility in polar organic solvents. The complex also had relatively strong acidity with a strength of 0.8 
       
  • 1,5-Stereocontrol in reactions of 2,4-disubstituted alk-2-enylstannanes
           with aldehydes; an approach to the stereoselective synthesis of branched
           triols
    • Abstract: Publication date: Available online 29 October 2019Source: TetrahedronAuthor(s): Eric J. Thomas, Daniel R. Tray 2-(tert-Butyldimethylsilyloxymethyl)-4-(methoxymethoxy)pent-2-enyl(tributyl)stannane is transmetallated by tin(IV) chloride stereoselectively to give a pent-1-en-3-ytin trichloride that reacts with aldehydes with excellent (E)-1,5-syn-stereocontrol, e.g. (3E)-1,5-syn-3-(tert-butyldimethylsilyloxymethyl)-5-(methoxymethoxy)-1-phenylhex-3-en-1-ol was the dominant product with benzaldehyde. The products from these reactions were taken through to more complex 2-substituted alk-2-enyl(tributyl)stannanes but only very low yields of the expected products were obtained from tin(IV) chloride mediated reactions of these stannanes and aldehydes. Nevertheless a stereoselective synthesis of 2-substituted 4-[(E)-2-alkoxypropylidene]tetrahydrofurans was developed.Graphical abstractImage 1
       
  • Evaluation of bifunctional chiral phosphine oxide catalysts for the
           asymmetric hydrosilylation of ketimines
    • Abstract: Publication date: Available online 28 October 2019Source: TetrahedronAuthor(s): Christopher J.A. Warner, Sian S. Berry, Simon Jones A series of bifunctional phosphine oxides have been prepared and evaluated as catalysts for the trichlorosilane mediated asymmetric hydrosilylation of ketimines. bis-Phosphine oxides, hydroxy-phosphine oxides, and biaryl phosphine oxides all demonstrated good catalytic activity, but poor to moderate enantioselectivity. A bis-P-chiral phosphine oxide displayed the highest enantioselectivity of 60%.Graphical abstractImage 1
       
  • Stephen G. Davies Honour Issue
    • Abstract: Publication date: Available online 28 October 2019Source: TetrahedronAuthor(s): Timothy J. Donohoe
       
  • Graphical abstract TOC
    • Abstract: Publication date: 15 November 2019Source: Tetrahedron, Volume 75, Issue 46Author(s):
       
  • Graphical abstract TOC
    • Abstract: Publication date: 15 November 2019Source: Tetrahedron, Volume 75, Issue 46Author(s):
       
  • 1-Methylthio-1-phenyl-1-silacyclohexane: Synthesis, conformational
           preferences in gas and solution by GED, NMR and theoretical calculations
    • Abstract: Publication date: 15 November 2019Source: Tetrahedron, Volume 75, Issue 46Author(s): Bagrat A. Shainyan, Elena N. Suslova, Tran Dinh Phien, Sergey A. Shlykov, Matthias Heydenreich, Erich Kleinpeter 1-Methylthio-1-phenyl-1-silacyclohexane 1, the first silacyclohexane with the sulfur atom at silicon, was synthesized and its molecular structure and conformational preferences studied by gas-phase electron diffraction (GED) and low temperature 13C and 29Si NMR spectroscopy (LT NMR). Quantum-chemical calculations were carried out both for the isolated species and solvate complexes in gas and in polar medium. The predominance of the 1-MeSaxPheq conformer in gas phase (1-Pheq:1-Phax = 55:45, ΔG° = 0.13 kcal/mol) determined from GED is consistent with that measured in the freon solution by LT NMR (1-Pheq:1-Phax = 65:35, ΔG° = 0.12 kcal/mol), the experimentally measured ratios being close to that estimated by quantum chemical calculations at both the DFT and MP2 levels of theory.Graphical abstractImage 1
       
  • Amphiphilic Dendrimer as Reverse Micelle: Synthesis, Characterization and
           Application as Homogeneous Organocatalyst
    • Abstract: Publication date: 15 November 2019Source: Tetrahedron, Volume 75, Issue 46Author(s): P.B. Sherly mole, Smitha George, A.M. Shebitha, V. Kannan, Suseela Mathew, K.K. Asha, K. Sreekumar The core and surface terminal groups are the two main catalytic sites in a dendrimer. In most of the reported examples, the catalytic sites in dendritic catalysis are the surface terminal functional groups. This perspective article concerned with the dendrimer based catalysis, involving these two catalytic sites and the dendrimer cavities. The interior cavities provide the nanoscale reactor sites, by creating reverse micelle like appearance for catalysis. In exploring the significant achievements in this area, a low generation PAMAM dendrimer with amphiphilic nature, having a polymeric core with large number of pendent amino groups was synthesized and concentrated its catalytic activity. The key features with respect to positive and/or negative catalytic activity was highlighted by synthesizing various aryl and heteroaryl 2-substituted benzimidazoles. The synthesized dendritic organocatalyst was proved to be amazingly reactive and gave high yield of products within a few minutes at room temperature with low catalyst loading. Here, a new stable hemiaminal, the species rarely been detected and much less isolated in bulk, was obtained during the synthesis of benzimidazoles. Moreover, this is the first reported method for the synthesis of benzimidazoles, using the homogeneous PAMAM dendrimer as a basic organocatalyst.Graphical abstractImage 1
       
  • A new tridentate fluorescent-colorimetric chemosensor for copper(II) ion
    • Abstract: Publication date: 15 November 2019Source: Tetrahedron, Volume 75, Issue 46Author(s): Zhi-Xiang Zhao, Ze-Liang Hu, Xian-Tao Zhang, Qing-Xiang Liu A new tri-imidazolium salt, tris(4-(3-(2-((8-hydroxy-9,10-dioxo-9′,10′-dihydroanthracen-1-yl)oxy)ethyl)-1H-imidazole-3′-ium-1′-yl)phenyl)amine hexafluorophosphate was prepared and characterized. Particularly, the recognition performance of the tri-imidazolium salt for cations was investigated through fluorescence and ultraviolet titrations, MS, IR spectra and 1H NMR titrations. The results indicated that the tri-imidazolium salt can distinguish effectively copper(II) ion from other cations by the changes of spectroscopy and colour (from yellow to orange under sunlight). Furthermore, the tri-imidazolium salt was also used in detecting Cu2+ through employing smartphone with the computed detection limit down to 0.51 μM.Graphical abstractImage 1
       
  • Diastereoselective heterocyclization of geminal bromo-fluoro
           arylcyclopropanes by nitrosonium tetrafluoroborate: Access to
           4-fluorinated isoxazolines and isoxazoles
    • Abstract: Publication date: 15 November 2019Source: Tetrahedron, Volume 75, Issue 46Author(s): Oksana B. Bondarenko, Arseniy I. Komarov, George L. Karetnikov, Svetlana N. Nikolaeva, Nikolai V. Zyk, Tina Holt, Andrei G. Kutateladze A series of 5-aryl-4-bromo-4-fluoroisoxazolines was synthesized via nitrosation of 2-aryl-1-bromo-1-fluorocyclopropanes with NOBF4. It was shown that the E-isomers of the cyclopropanes react highly regio- and diastereoselectively leading exclusively to the E-isomers of the isoxazolines. The obtained 5-aryl-4-bromo-4-fluoroisoxazolines were transformed selectively into the corresponding 5-aryl-4-fluoro- or 5-aryl-4-bromoisoxazoles in good yields in the reaction with Lewis acids.Graphical abstractImage 1
       
  • Progress towards metal-free radical alkylations of quinones under mild
           conditions
    • Abstract: Publication date: 15 November 2019Source: Tetrahedron, Volume 75, Issue 46Author(s): Jordan D. Galloway, Ryan D. Baxter A new method for the radical alkylation of quinones is reported. Lewis basic nitrogen additives increase the efficacy of quinone alkylations from carboxylic acids using catalytic AgNO3 and Selectfluor as a mild oxidant. Electrochemical data suggests that certain Lewis basic additives are capable of directly reducing Selectfluor through a single-electron transfer, presumably via a charge-transfer complex. This process yields intermediates capable of promoting oxidative decarboxylation of alkyl carboxylic acids without an added metal initiator. Using this strategy, we have demonstrated progress towards a metal-free C–H quinone alkylation reaction that proceeds at room temperature under mild conditions.Graphical abstractImage 1
       
  • NH4I/1,10-phenanthroline catalyzed direct sulfenylation of N-heteroarenes
           with ethyl arylsulfinates
    • Abstract: Publication date: 15 November 2019Source: Tetrahedron, Volume 75, Issue 46Author(s): Lingjuan Chen, Jun Zhang, Yueting Wei, Zhen Yang, Ping Liu, Jie Zhang, Bin Dai An efficient synthesis of N-heterocyclic aryl sulfides via NH4I/1,10-phenanthroline-catalyzed direct sulfenylation reactions was reported. In this reaction, heteroarenes such as indoles, and pyrroles serve as nucleophiles by installing a arylthio group at the C3 and C2 position of heterocycles, respectively. With readily accessible and free of unpleasant odor ethyl arylsulfinates as sulfur reagents, the metal-free-catalyzed direct sulfenylation of N-heteroarenes has been developed. 3-Arylthio-indoles and 2-arylthio-pyrroles derivatives were obtained in moderate to excellent yields, even on gram scale. The reaction was general for a broad scope of substrates and demonstrated good tolerance to a variety of functional groups.Graphical abstractImage 1
       
  • Syntheses and properties of linear π-conjugated molecules composed of
           1-azaazulene and azulene
    • Abstract: Publication date: 15 November 2019Source: Tetrahedron, Volume 75, Issue 46Author(s): Keito Ohtsu, Ryohei Hayami, Takuya Sagawa, Satoru Tsukada, Kazuki Yamamoto, Takahiro Gunji Two compounds, 6-(1-azaazulen-2-yl)ethynylazulene (8) and 6-(2-azulenyl)ethynylazulene (10), were synthesized using the Sonogashira-Hagihara cross-coupling reaction followed by decarboxylation with concentrated phosphoric acid. Compounds 8 and 10 were characterized by 1H and 13C nuclear magnetic resonance (NMR) spectroscopy, mass spectrometry, ultraviolet–visible (UV–Vis) spectroscopy, cyclic voltammetry, and density functional theory (DFT) calculations. Based on the results, both compounds were confirmed to have π-conjugation throughout their molecular structures. The acidic responsivity of compounds 8 and 10 was evaluated using UV–Vis and 1H NMR spectroscopy. Compound 8 was found to be highly sensitive to trifluoroacetic acid, with its 1-azaazulenyl moiety acting as a base. Compound 10 generated azulenium cations when mixed with excess amounts of trifluoroacetic acid.Graphical abstractSynthesized compounds 6-(1-azaazulen-2-yl)ethynylazulene (8) and 6-(2-azulenyl)ethynylazulene (10) had the simplest structures of the ethynylene-bridged linear π-conjugated compounds composed of 1-azaazulene-azulene and azulene-azulene, respectively. Expansion of their conjugated systems was confirmed by UV–Vis spectroscopy and density functional theory (DFT) calculations.Image 1
       
  • Concise design and synthesis of pyridine-fused heterocycles via
           6π-Azaelectrocyclization process of iminoalkyne derivatives
    • Abstract: Publication date: 15 November 2019Source: Tetrahedron, Volume 75, Issue 46Author(s): Kıvılcım Şendil, Selbi Keskin, Metin Balci A concise and regioselective approach to the synthesis of pyridine-fused heterocycles and benzoxazepine derivatives was developed. Propargyl imines derived from aromatic aldehydes and propargyl amine underwent 6π-electrocyclization reactions at high temperatures in high yields to form pyridine-fused heterocycles. Application of the same methodology to aromatic imines having a hydroxyl group in the ortho position resulted in the formation of (benz)oxazepine derivatives. The formation mechanism of the products was discussed.Graphical abstractImage 1
       
  • Investigations of an annulation-fragmentation-spirocyclisation approach to
           fawcettimine-type Lycopodium alkaloids
    • Abstract: Publication date: 15 November 2019Source: Tetrahedron, Volume 75, Issue 46Author(s): Kang Yee Seah, Jeremy Robertson This paper reports progress in the development of a furan oxidative N-spirocyclisation approach to the fawcettimine alkaloids huperzine Q and lycopladine D. A short synthesis is described of a key intermediate cyclopentaindolizidine that subsequently fragments by N-acylation and β-elimination. The stereochemistry of 1,4-addition of cyanide to the resulting enone is discussed with supporting molecular modelling calculations. N-Deprotection is shown to be accompanied by cyclisation onto the nitrile group, resulting in a tricyclic lactam with a twisted amide functionality. Elaboration of this lactam afforded four of the five rings present in lycopladine D with just the C(8) carbon lacking.Graphical abstractImage 1
       
  • Graphical abstract TOC cont'd
    • Abstract: Publication date: 15 November 2019Source: Tetrahedron, Volume 75, Issue 46Author(s):
       
  • Visible-light mediated regioselective approach towards synthesis of
           7-aroyl-6-methyl-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazines
    • Abstract: Publication date: Available online 25 October 2019Source: TetrahedronAuthor(s): Ranjana Aggarwal, Shilpa Sharma, Mona Hooda, Dionisia Sanz, Rosa M. Claramunt, Brendan Twamley, Isabel Rozas The first visible-light mediated, simple, efficient and ecofriendly protocol for the regioselective synthesis of novel [1,2,4]triazolo[3,4-b][1,3,4]thiadiazines has been developed by the reaction of α-bromodiketones, generated in situ by the bromination of a diverse array of β-diketones with N-bromosuccinimide, with 4-amino-[1,2,4]triazole-3-thiols. The methodology does not require the presence of any additives and this reaction proceeded in the presence of EDG (OMe), EWG (Cl) and heteroarenes (thiophenyl) giving the expected products in good to excellent yields. A solvent free protocol was also established to accomplish the synthesis of target compounds but it required PTSA as a catalyst and yields are comparatively poor. The structure of the regioisomer has been confirmed unambiguously by heteronuclear 2D-NMR [(1H-13C) HMBC, (1H-15N) HMBC, (1H-13C) HMQC] spectroscopic and X-ray crystallographic studies.Graphical abstractImage 1
       
  • Inunicosides A−K, rare polyacylated ent-kaurane diterpenoid glycosides
           from the flowers of Inula japonica
    • Abstract: Publication date: Available online 25 October 2019Source: TetrahedronAuthor(s): Zhi-Pu Yu, Jin-Hai Yu, Jun-Sheng Zhang, Shu-Juan Yu, Hua Zhang Inunicosides A−K (1–11), eleven unusual polyacylated ent-kaurane diterpenoid glycosides, were isolated from the flowers of a traditional Chinese herbal plant Inula japonica. Their structures with absolute configurations were determined on the basis of comprehensive spectroscopic analyses, chemical degradation, enzymatic hydrolysis and ECD experiments. Among these isolates, inunicoside K (11) showed mild antibacterial activity against Staphylococcus aureus ATCC 25923. Diterpene constituents have been rarely reported in the Inula species, and thus the discovery of this panel of compounds greatly enriches the chemical diversity of metabolites from the genus Inula.Graphical abstractImage 1
       
  • Oxidative synthesis of Benzo[1,4]oxazines from α-branched primary amines
           and ortho-benzoquinones
    • Abstract: Publication date: Available online 24 October 2019Source: TetrahedronAuthor(s): Dhananjayan Vasu, Jamie A. Leitch, Darren J. Dixon The efficient oxidative construction of benzo[1,4]oxazines from simple α-branched amines and ortho-benzoquinones is reported. The procedure pivots on a triethylamine and iodine mediated oxidative ring closure from the ketimine intermediate formed upon their condensation. This reaction was shown to tolerate a variety of α-branched benzylamines and downstream derivatization to substituted benzomorpholine structures was also demonstrated.Graphical abstractImage 1
       
  • Asymmetric syntheses of fagomine and its stereoisomers
    • Abstract: Publication date: Available online 23 October 2019Source: TetrahedronAuthor(s): Stephen G. Davies, Ai M. Fletcher, Paul M. Roberts, James E. Thomson d-fagomine (1,2,5-trideoxy-1,5-imino-D-arabino-hexitol), a naturally occurring polyhydroxylated piperidine (iminosugar), and its stereoisomers display important biological activities such as glycosidase inhibition. This review delineates both de novo asymmetric and enantiospecific syntheses of fagomine and its stereoisomers.Graphical abstractImage 1
       
  • Transition Metal-free Strategies for the Stereoselective Construction of
           Spirocyclopropyl Oxindoles
    • Abstract: Publication date: Available online 23 October 2019Source: TetrahedronAuthor(s): Emily P. Bacher, Brandon L. Ashfeld The spirocyclopropyl oxindole motif is an important architectural subunit as a well-established pharmacophore that is present in many biologically active natural products and small molecules with applications across a wide array of therapeutic areas. As a result, efforts toward the stereoselective assembly of this core framework has played a role in the recent resurgence of metal-free cycloaddition strategies. This review covers those recent transition metal-free approaches to the spirocyclopropyl oxindole framework proceeding with high levels of diastereoselectivity as classified into three reagent-based classifications: 1) cyclopropanations employing diazo compounds, 2) PL3-mediated cyclopropanations, and 3) organocatalyzed formal [2+1]-cycloadditions.Graphical abstractImage 1
       
  • Hot-spot guided design of macrocyclic inhibitors of the LSD1-CoREST1
           interaction
    • Abstract: Publication date: Available online 23 October 2019Source: TetrahedronAuthor(s): Peter ‘t Hart, Joseph Openy, Adrian Krzyzanowski, Hélène Adihou, Herbert Waldmann New modalities such as cyclic peptides are attractive structures to inhibit challenging targets. The interaction between LSD1 and CoREST1 is required for histone demethylation and represents an attractive therapeutic target. The large interaction surface between these two proteins was analyzed by virtual alanine scanning using DrugScore PPI and a cluster of hot-spot residues was identified on CoREST1. The cluster was converted into a series of cyclic peptides and the inhibitory potency was optimized by stereochemical inversion at one of the amino acids alpha carbons combined with modification of amino acid side chains. Active peptides were further studied by variable temperature 1H-NMR and docking to evaluate the effect of conformation on binding. Potent inhibitors of the challenging PPI were obtained and will allow future optimization into more druglike structures.Graphical abstractImage 1
       
  • Bifunctional probe for Cu2+/Al3+ based on a diarylethene with a 4,
           5-[bis-(5-ethylacetate-yl)-2-thienyl]-1H-imidazole unit
    • Abstract: Publication date: Available online 22 October 2019Source: TetrahedronAuthor(s): Lu Diao, Renjie Wang, Yunfei Liang, Yaming Xue, Gang Liu, Shouzhi Pu A new asymmetric perfluordiarylethene (1O) was synthesized using 4, 5-[bis-(5-ethylacetate-yl)-2-thienyl]-1H-imidazole as a functional group. 1O exhibited favorable reversible cyclization and cycloreversion reactions upon alternating irradiation with UV and visible light. Both of its open- and closed-ring isomers were found to be highly selective towards Cu2+ with significant absorption and color changes, which could be used as a ‘naked-eye’ colorimetric sensor for Cu2+ detection. Upon exposure to acid, its fluorescence dramatically enhanced by 14-fold with a color change from dark to bright cyan due to the formation of the protonated compound. Moreover, 1O showed obvious fluorescence “turn-on” signal response towards Al3+, and the detection limit for Al3+ was determined to be 4.8 × 10−9 mol L−1. Based on the fluorescence signals of 1O, a combinational stimuli logic circuit were designed by using the fluorescence intensity as the output signal with the inputs of lights, Al3+ and EDTA. Finally, 1O could be used as a biological probe for detecting intracellular Al3+ in a physiological environmental.Graphical abstractImage 1
       
  • Redox-neutral photocatalytic cyanomethylation/cyclization cascade of
           olefinic amides: Access to cyanomethylated benzoxazines
    • Abstract: Publication date: Available online 22 October 2019Source: TetrahedronAuthor(s): Liang Liu, Yan-Hong He, Zhi Guan A visible-light-induced photocatalytic cyanomethyl radical addition/intramolecular cyclization cascade reaction of olefinic amides has been developed under mild conditions. This reaction provides a novel method for the synthesis of various cyanomethyl-containing benzoxazines, which are useful pharmaceutical framework. The method exhibits good functional group tolerance and a wide range of substrate scope.Graphical abstractImage 1
       
  • Palladium-catalyzed one-pot construction of difluorinated 1,3-enynes from
           α,α-iododifluoroacetones and alkynes
    • Abstract: Publication date: Available online 22 October 2019Source: TetrahedronAuthor(s): Xing Wang, Jian Hu, Jie Ren, Tianci Wu, Jingjing Wu, Fanhong Wu A palladium-catalyzed one-pot difunctionalization of alkynes with α,α-iododifluoroacetones is introduced for the synthesis of difluorinated 1,3-enynes. The reaction proceeds through the radical addition of RCOCF2 radical to alkynes and subsequent Sonogashira coupling with the same alkynes to give the 1,3-enyne products with high regio and stereoselectivity.Graphical abstractImage 1
       
  • Effects of fluorine substituent on properties of cyclometalated
           iridium(III) complexes with a 2,2′-bipyridine ancillary ligand
    • Abstract: Publication date: Available online 16 October 2019Source: TetrahedronAuthor(s): Yan Chen, Chun Liu, Lei Wang Cationic cyclometalated Ir(III) complexes (Ir1-Ir5) with fluorine-substituted 2-phenylpyridine (ppy) derivatives as CˆN cyclometalating ligands and 2,2′-bipyridine (bpy) as the ancillary ligand, have been synthesized and fully characterized. The influences of the number and the position of fluorine atoms at the cyclometalating ligands on the photophysical, electrochemical and oxygen sensing properties of the Ir(III) complexes have been investigated systematically. The introduction of fluorine on the CˆN cyclometalating ligands of the complexes results in blue-shifts of the maximum emission wavelengths, and increases in the photoluminescence quantum yields (ΦPL), phosphorescence lifetimes and energy gaps, compared to the non-fluorinated [Ir(ppy)2(bpy)]+PF6− (Ir0). Among them, 2-(2,4-difluorophenyl)pyridine-derived Ir4 shows the maximum blue-shift (514 nm vs. 575 nm for Ir0) and the highest ΦPL (50.8% vs. 6.5% for Ir0). The complex Ir3 with 2-(4-fluorophenyl)-5-fluoropyridine as CˆN ligand exhibits the highest oxygen sensitivity and excellent operational stability in 10 cycles within 4000 s.Graphical abstractImage 1
       
  • Synthesis and studies of crowned dipyrromethenes based macrocycles
    • Abstract: Publication date: Available online 13 October 2019Source: TetrahedronAuthor(s): Belarani Ojha, Ankit Kumar, Kishor G. Thorat, Mangalampalli Ravikanth Three different meso-substituted new type of crowned dipyrromethene macrocycles were synthesized in decent yields over a sequence of four simple reaction steps using readily available precursors. The macrocycles were thoroughly characterized by HRMS as well as 1D and 2D NMR spectroscopic techniques and the structures of one of the macrocyles in its neutral form and protonated form were determined by X-ray crystallography. The crystal analysis indicated that the macrocycle was distorted in both neutral and protonated forms owing to the presence of flexible aliphatic ether chain. Absorption and electrochemical studies indicated that the properties of macrocycles were dependent on type of aryl group present at the meso-position of dipyrrin moiety of crowned dipyrromethene macrocycle. The preliminary studies indicated that the crowned dipyrromethene macrocycles can act as specific colorimetric optical sensor for Cu2+ ion.Graphical abstractImage 1
       
  • Synthesis of α,β-dibromo ketones by photolysis of α-bromo ketones with
           N-bromosuccinimide: Photoinduced β-bromination of α-bromo ketones
    • Abstract: Publication date: Available online 13 October 2019Source: TetrahedronAuthor(s): Da Yoon Moon, Sejin An, Bong Ser Park Irradiation of α-bromopropiophenones in the presence of NBS results in the formation of α,β-dibromopropiophenones, which can be viewed as β-bromination of α-bromopropiophenones. The reaction is believed to go through a series of reactions; photoinduced C–Br bond cleavage, elimination of HBr to give α,β-unsaturated ketone intermediates, and addition of Br2, which are formed by the reaction between HBr and NBS. From mechanistic studies of the reaction, we have also found a very convenient method for α-debromination of the α,β-dibromopropiophenones which is by simple irradiation of the dibromo ketones in acetone or 2-propanol without the use of any additives. Our results demonstrate that bromine can be added into or eliminated from the alpha, beta, or both positions to the carbonyl group by photochemical methods, which make synthetic options of bromine containing carbonyl compounds versatile.Graphical abstractImage 1
       
 
 
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