Tetrahedron Letters

Editorial board ()
Publication date: 15 February 2017 Source:Tetrahedron Letters, Volume 58, Issue 7
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Acetone promoted 1,4-migration of an alkoxycarbonyl group on a syn-1,2-diamine ()
Publication date: 15 February 2017 Source:Tetrahedron Letters, Volume 58, Issue 7 Author(s): Tanya Napolitano, Shu-Yuan Cheng, Brooke Nielsen, Christopher Choi, William Aguilar, Manuel M. Paz, Anne-Marie Sapse, Elise Champeil A 2-protected cis-amino mitosene undergoes an irreversible acetone promoted isomerization and converts to the 1-isomer. Kinetic studies and DFT calculations of the reaction are reported. An organocatalytic mechanism is proposed, involving a covalent intermediate formed by reaction of the mitosene and acetone. Graphical abstract image
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Diastereoselective synthesis of the 5-hydroxy-pyrrolidinone amino acid of the microsclerodermins and model studies for an end-game strategy for microsclerodermin B ()
Publication date: 15 February 2017 Source:Tetrahedron Letters, Volume 58, Issue 7 Author(s): Christian Winter, Robert D.C. Pullin, Timothy J. Donohoe The first diastereoselective synthesis of the 5-hydroxy-pyrrolidinone amino acid common to eight members of the microsclerodermin family is presented. Our strategy involves formal hydration of an unsaturated precursor via the use of a two-step hydroxybromination-debromination protocol; this procedure provides exclusively the requisite 4,5-cis-pyrrolidinone. Furthermore model studies are presented that indicated the potential viability of this hydration strategy in the context of a synthesis of microsclerodermin B. Graphical abstract image
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Stereoselective synthesis of (−)-3-PPP through palladium-catalysed unactivated C(sp3)–H arylation at the C-3 position of l-pipecolinic acid ()
Publication date: 15 February 2017 Source:Tetrahedron Letters, Volume 58, Issue 7 Author(s): Shi-Jin Zhang, Wen-Wu Sun, Qun-Ying Yu, Pei Cao, Xiao-Ping Dong, Bin Wu An efficient route for the preparation of (−)-3-PPP(preclamol) using the highly stereoselective palladium-catalysed C(sp3)-H arylation and radical decarboxylation reaction as the key steps is described. The chiral center at the C-3 position of l-pipecolinic acid derivative formed in the key reaction was completely induced by the adjacent stereocenter of the substrate, which was confirmed by the data of chiral HPLC analysis. Substitution effect of nitrogen on the efficiency of Pd-catalysed C(sp3)-H arylation reaction was explored with substantial experiments including the X-ray single-crystal diffraction analysis of palladium-complex-2. Graphical abstract image
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Improvement of stability of phenacyloxycarbamidomethyl (Pocam) group, a cysteine protecting group removable with zinc reduction, under acidic conditions ()
Publication date: 15 February 2017 Source:Tetrahedron Letters, Volume 58, Issue 7 Author(s): Hidekazu Katayama, Takuma Goto In order to improve the stability of phenacyloxycarbamidomethyl (Pocam) group, a cysteine protecting group removable with zinc reduction, under acidic conditions, various alkyl substituents on the nitrogen atom of Pocam group were examined. As a result, attachment of an electron-withdrawing group improved the stability, and 2,2,2-trifluoroethyl (Tfe) group was most effective among four substituents tested. Tfe-Pocam group could be used in solid-phase peptide synthesis and peptide condensation reactions, and it was also useful for regioselective disulfide formation reactions. Graphical abstract image
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Palladium-catalyzed acetoxylation of arenes by 1,2,3-triazole-directed CH activation ()
Publication date: 15 February 2017 Source:Tetrahedron Letters, Volume 58, Issue 7 Author(s): Fen Zhao, Zhen Chen, Xinyuan Ma, Shaojun Huang, Yubo Jiang A facile and efficient method for the regioselective acetoxylation of 1,4-disubstituted 1,2,3-triazoles via Pd-catalyzed C H bond activation was developed. The cheap acetic acid was applied as the acetoxyl source to convert aromatic sp 2 C H bonds into C O bonds in high regioselectivity, employing 1,2,3-triazole as an elegant directing group and K2S2O8 as the oxidant. A range of 1,2,3-triazoles bearing acetoxyl group can be synthesized with the reaction facilely. Graphical abstract image
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One-pot syntheses of α,α-dibromoacetophenones from aromatic alkenes with 1,3-dibromo-5,5-dimethylhydantoin ()
Publication date: 15 February 2017 Source:Tetrahedron Letters, Volume 58, Issue 7 Author(s): Ping Wu, Senhan Xu, Hao Xu, Haiyan Hu, Wei Zhang A novel method for the preparation of α,α-dibromoacetophenones from aromatic alkenes was reported. This procedure was mediated by 1,3-dibromo-5,5-dimethylhydantoin, which served as bifunctional reagent, proceeding oxidation and bromination in one-pot. Graphical abstract image
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Cascade synthesis of selective dihydro pyridazino fused acridinone derivatives via MCM-41 catalyzed ring-opening/ring-closure reaction ()
Publication date: 15 February 2017 Source:Tetrahedron Letters, Volume 58, Issue 7 Author(s): Rajiv Karmakar, Asim Bhaumik, Biplab Banerjee, Chhanda Mukhopadhyay An enhanced one-pot synthesis of new functionalized 5,6-dihydro-5,5-dimethyl-2-phenyl-2H-pyridazino[3,4,5-kl]acridin-1(4H)-one derivatives with different substituted patterns by using mesoporous MCM-41 catalyst via a ring opening/ring closure reaction process has been established. This MCM-41 silica catalyst has been synthesized and characterized using an array of sophisticated analytical techniques like BET, XRD, UHRTEM, etc. This reaction could be conducted from inexpensive substrates within short period under neat reflux conditions. Compared with the usual methods, the remarkable advantages of this method are milder reaction conditions, operational simplicity, higher yields, short reaction times and an environmentally friendly procedure. Graphical abstract image
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Copper nanoparticles catalyzed N-H functionalization: An efficient solvent-free N-tert-butyloxycarbonylation strategy ()
Publication date: 15 February 2017 Source:Tetrahedron Letters, Volume 58, Issue 7 Author(s): Barnali Deb, Sudipto Debnath, Anindita Deb, Dilip K. Maiti, Swapan Majumdar A chemoselective transformation of amines to their tert-butyloxycarbonyl (Boc) protected derivatives (NBoc) is described using Cu-NPs under solvent-free conditions. Simple method, rapid reaction rate, mild conditions, tolerance of a wide range of functional groups, excellent yield, ease recovery and high catalytic turnover are the salient features of this approach. tert-Butyloxycarbonylation of chiral amino acid esters and amino alcohols were performed without racemization. Graphical abstract image
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Cereusitin A, a cyclic tetrapeptide from a Bacillus cereus strain isolated from the soft coral Antillogorgia (syn. Pseudopterogorgia) elisabethae ()
Publication date: 15 February 2017 Source:Tetrahedron Letters, Volume 58, Issue 7 Author(s): Angela Pinzón-Espinosa, Diana Martinez-Matamoros, Leonardo Castellanos, Carmenza Duque, Jaime Rodríguez, Carlos Jiménez, Freddy A. Ramos Two new compounds, cereusitin A (1), the tetrapeptide cyclo-(L-phenylalanyl-trans-4-hydroxy-L-prolyl-L-leucyl-trans-4-hydroxy-L-proline and 4-(R)-hydroxysattabacin (2), along with the methyl, isopropyl, and propyl esters of p-hydroxybenzoic acid (3–5) were isolated from the organic extracts of the culture of the B. cereus RKHC-09 strain in two culture media (MOLP and B1), recovered from the sea fan Antillogorgia elisabethae (syn. Pseudopterogorgia elisabethae). Cereusitin A (1) showed mild antifungal activity against Colletotrichum gloeosporoides C26 (yam pathogen) but was inactive against Fusarium oxysporum f.sp. dianthi (carnation pathogen). The methyl and propyl esters of p-hydroxybenzoic acid (4 and 5) showed antimicrobial activity against S. aureus ATCC 33591 and S. cerevisiae, with an MIC of 2μM. Graphical abstract image
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Green synthesis of halogenated thiophenes, selenophenes and benzo[b]selenophenes using sodium halides as a source of electrophilic halogens ()
Publication date: 15 February 2017 Source:Tetrahedron Letters, Volume 58, Issue 7 Author(s): Tanay Kesharwani, Krystal A. Giraudy, Jordan L. Morgan, Cory Kornman, Abayomi D. Olaitan Herein, we report the first synthesis of chlorinated benzo[b]selenophenes via environmentally friendly electrophilic chlorocyclization reaction using “table salt” as a source of “electrophilic chlorine” and ethanol as a solvent. In addition, the synthesis of diverse halogenated heterocycles, including 3-chloro, 3-bromo and 3-iodo thiophenes, selenophenes, and benzo[b]selenophenes was successfully accomplished under the same environmentally benign reaction conditions. This methodology has several advantages over other previously reported reactions as it employs simple starting compounds, an environmentally friendly solvent, ethanol, and non-toxic inorganic reagents under mild reaction conditions, resulting in the high product yields. Graphical abstract image
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Synthesis and antiviral evaluation of 2′,2′,3′,3′-tetrafluoro nucleoside analogs ()
Publication date: 15 February 2017 Source:Tetrahedron Letters, Volume 58, Issue 7 Author(s): Ozkan Sari, Leda Bassit, Christina Gavegnano, Tamara R. McBrayer, Louise McCormick, Bryan Cox, Steven J. Coats, Franck Amblard, Raymond F. Schinazi Herein, we report the synthesis of novel 2′,2′,3′,3′-tetrafluorinated nucleoside analogs along with their phosphoramidate prodrugs. A tetrafluoro ribose moiety was coupled with different Boc/benzoyl-protected nucleobases under Mitsunobu conditions. After deprotection, tetrafluorinated nucleosides 13b, 14b, 20b-22b were reacted with phenyl-(isopropoxy-l-alaninyl)-phosphorochloridate to afford corresponding monophosphate prodrugs 24b–28b. All synthesized compounds were evaluated against several DNA and RNA viruses including HIV, HBV, HCV, Ebola and Zika viruses. Graphical abstract image
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Rapid aerobic iodination of arenes mediated by hypervalent iodine in fluorinated solvents ()
Publication date: 15 February 2017 Source:Tetrahedron Letters, Volume 58, Issue 7 Author(s): Jernej Iskra, S. Shaun Murphree Arenes are rapidly converted to the corresponding iodides by aerobic oxidative iodination at room temperature by treatment with iodine and catalytic quantities of nitrous acid in a fluorinated solvent. Dichloroiodic acid is proposed as the actual iodination reagent. Graphical abstract image
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Piperidine promoted aldol reaction of alkynyl aldehydes and ethyl diazoacetate ()
Publication date: 15 February 2017 Source:Tetrahedron Letters, Volume 58, Issue 7 Author(s): Guifu Zhang, Sheng Sun, Longqiang Jiang, Shaofa Sun, Xing Luo, Zhi Chen, Haibing Guo, Yalan Xing Complex diazo compounds containing propargyl alcohol functional group were prepared by an efficient aldol reaction of alkynyl aldehydes and ethyl diazoacetate in good yields. Piperidine was utilized as a base to catalyze this transformation. The aldol reaction showed broad substrate scopes and good functional group compatibility. Graphical abstract image
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Aerobic oxidation of secondary alcohols in water with ABNO/tert-butyl nitrite/KPF6 catalytic system ()
Publication date: 15 February 2017 Source:Tetrahedron Letters, Volume 58, Issue 7 Author(s): Jiaqi Ma, Chao Hong, Yan Wan, Meichao Li, Xinquan Hu, Weimin Mo, Baoxiang Hu, Nan Sun, Liqun Jin, Zhenlu Shen A green and efficient transition-metal free ABNO/tert-butyl nitrite/KPF6-catalyzed aerobic oxidation of secondary alcohols in water has been achieved. Under the optimal reaction conditions, a number of secondary aliphatic alcohols and secondary benzylic alcohols can be converted to their corresponding ketones in excellent yields (up to 99%). Graphical abstract image
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Visible-light assisted one-pot preparation of aryl glyoxals from acetoarylones via in-situ arylacyl bromides formation: Selenium-free approach to acetoarylones oxidation ()
Publication date: 15 February 2017 Source:Tetrahedron Letters, Volume 58, Issue 7 Author(s): Palani Natarajan, Manjeet, Naveen Kumar, Sapna Devi, Kalyani Mer A novel visible-light (blue LEDs: hν =425±15nm) photocatalyzed one-pot method for the synthesis of electronically diverse aryl glyoxals in good to excellent yields from acetoarylones and green regents such as air, vitamin C and dioxane dibromide has been described. In addition, an application of the current methodology has been demonstrated for the oxidation of monoamine oxidase-B inhibitors, i.e., 1-(4-((4-fluorobenzyl)oxy)phenyl)ethanone and 1-(3-((4-chlorobenzyl)oxy)phenyl)ethanone. This finding may serves as a valuable alternative to the traditional acetoarylones oxidation reactions conducted using selenium dioxide a harmful and unselective reagent known to simultaneously oxidize allylic, benzylic, CH3 and so on. Graphical abstract image
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Nodupetide, a potent insecticide and antimicrobial from Nodulisporium sp. associated with Riptortus pedestris ()
Publication date: 15 February 2017 Source:Tetrahedron Letters, Volume 58, Issue 7 Author(s): Hui Min Wu, Li Ping Lin, Qin Lan Xu, Wen Bo Han, Song Zhang, Ze Wen Liu, Ya Ning Mei, Zhu Jun Yao, Ren Xiang Tan Nodupetide (1), a new cyclodepsipeptide unique in its incorporation of a 3-hydroxy-4-methylhexanoic acid (HMHA) derived motif, was discovered from Nodulisporium sp. IFB-A163, a fungus residing in the insect (Riptortus pedestris) gut. The nodupetide structure was elucidated by its MS/MS and 2D NMR spectra, and its absolute configuration by the X-ray crystallography and modified Marfey’s method. Nodupetide is insecticidal against rice brown planthopper (Nilaparvata lugens) with an LD50 value of 70ng/larva, and inhibitory towards the drug-resistant human pathogenic bacterium Pseudomonas aeruginosa with its MIC value (5.0μM) comparable to that (3.2μM) of ciprofloxacin, a prescribed antibacterial agent co-assayed equally. Graphical abstract image
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Synthesis of 2-arylindoles by Suzuki coupling reaction of 3-bromoindoles with hindered benzoboronic acids ()
Publication date: 15 February 2017 Source:Tetrahedron Letters, Volume 58, Issue 7 Author(s): Guizhou Yue, Yao Wu, Caimei Wu, Zhongqiong Yin, Huabao Chen, Xianxiang Wang, Zuming Zhang A new synthetic method for 2-arylindoles has been developed, the process through Suzuki coupling reaction of 3-bromoindoles with hindered boronic acid catalyzed by Pd(OAc)2/PCy3, and a series of 2-arylindoles have been synthesized in moderate to high yields. Graphical abstract image
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Synergistic copper-TEMPO catalysis of intermolecular vicinal diamination of styrenes ()
Publication date: 15 February 2017 Source:Tetrahedron Letters, Volume 58, Issue 7 Author(s): Shiue-Shien Weng, Kun-Yi Hsieh, Zih-Jian Zeng, Jia-Wei Zhang A copper-catalyzed, 2,2,6,6-tetramethyl piperidine N-oxy radical-assisted intermolecular diamination of styrenes with N-fluorobenzenesulfonimide has been developed. The current protocol proved amenable to a diverse array of styrenes via cascade radical addition to readily afford synthetically useful aromatic vicinal diamines with exclusive diastereoselectivity. Graphical abstract image
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Manganese (III) acetate mediated synthesis of polysubstituted pyrroles under solvent-free ball milling ()
Publication date: 15 February 2017 Source:Tetrahedron Letters, Volume 58, Issue 7 Author(s): Ji-Chao Zeng, Hui Xu, Fei Yu, Ze Zhang Under solvent-free ball milling conditions, a simple and mild method was developed for efficient synthesis of 2,5-dimethyl-3,4-dicarboxylate-pyrroles and N-substituted 3,4-diphenylpyrroles via condensation-annulation of amines with acetoacetate and 2-phenylacetaldehyde, respectively. The use of cheap and safe Mn(OAc)3 as a mediator, no use of commonly employed acetic acid as solvent, short reaction time and readily available starting materials make this protocol a good alternative to traditional synthesis of polysubstituted pyrroles. Graphical abstract image
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Azo-pyrene–based fluorescent sensor of reductive cleavage of isomeric azo functional group ()
Publication date: 15 February 2017 Source:Tetrahedron Letters, Volume 58, Issue 7 Author(s): Han Na Joo, Binh huy Le, Young Jun Seo In this study we investigated the reductive azo cleavage of an azo compound presenting a pyrene fluorophore (Azo-py). Because of dramatic changes in its fluorescence, Azo-py could be used as a monitoring system for the reductive azo cleavage. Electron transfer from the pyrene unit to the azo moiety induced fluorescence quenching; this quenched fluorescence was recovered after the reductive azo cleavage. IR and NMR spectroscopy were used to study the various structural states. The rate of reductive cleavage of the azo compound, determined through fluorescence monitoring, depended on its structural state: the cleavage of trans-Azo-py was much faster than that of the cis-Azo-py. Furthermore, the Azo-py fluorophore was highly sensitive to the presence of zinc, but not other metal compounds, and the pH. Graphical abstract image
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The Beckmann fragmentation of quadricyclanone oxime ()
Publication date: 15 February 2017 Source:Tetrahedron Letters, Volume 58, Issue 7 Author(s): Filip Gracias, Hana Dvořáková, Tomáš Martinů The attempted O-tosylation of tetracyclo[3.2.0.02,7.04,6]heptan-3-one (quadricyclanone) oxime with p-toluenesulfonyl chloride in dichloromethane in the presence of triethylamine/DMAP or pyridine resulted in the Beckmann fragmentation to give a mixture of 4-exo-/4-endo-tosyloxy- and 4-exo-/4-endo-chlorobicyclo[3.1.0]hex-2-ene-6-endo-carbonitriles in 90% overall yield. Solvolysis of all four products in 2,2,2-trifluoroethanol afforded the corresponding 4-exo-trifluoroethoxy derivative as the sole product. Quadricyclanone itself undergoes the fragmentation reaction with hydroxylamine-O-sulfonic acid, selectively affording the 4-exo-hydroxy-6-endo-nitrile in 90% isolated yield. Graphical abstract image
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A novel lutetium(III) acetate phthalocyanine directly substituted with N,N’-dimethylaminophenyl groups via CC bonds and its water-soluble derivative for photodynamic therapy ()
Publication date: 15 February 2017 Source:Tetrahedron Letters, Volume 58, Issue 7 Author(s): Shaya Y. Al-Raqa, Baybars Köksoy, Mahmut Durmuş In this study, the novel 4-(N,N′-dimethylamino)phenyl substituted lutetium(III) acetate phthalocyanine (2) and its quaternized derivative (3) were synthesized via a Suzuki-Miyaura coupling reaction between tetrakis(iodo) lutetium(III)acetate phthalocyanine (1) and 4-(N,N-dimethylamino)phenylboronic acid, and subsequent quaternization using dimethyl sulfate, respectively. The obtained phthalocyanine 3 exhibited excellent solubility in water which is important for photodynamic therapy applications. Photophysical properties such as fluorescence quantum yield and fluorescence lifetime, and photochemical properties such as singlet oxygen generation and photostability were investigated to determine their suitability for photodynamic therapy. The lutetium(III) phthalocyanines, especially quaternized derivative 3, showed promising properties as potential photosensitizers for the treatment of cancer, producing higher singlet oxygen (ΦΔ =0.59) than motexafin lutetium (ΦΔ =0.31) which is a clinically used lutetium texaphyrin photosensitizer. Graphical abstract image
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Generation of trifluoromethyl thiolsulphonate through one-pot reaction of sulfonyl chloride and trifluoromethanesulfanylamides ()
Publication date: 15 February 2017 Source:Tetrahedron Letters, Volume 58, Issue 7 Author(s): Yuewen Li, Guanyinsheng Qiu, Hailong Wang, Jie Sheng A novel and efficient tandem reaction of sulfonyl chloride and trifluoromethylsulfanylamide is described here for the synthesis of various trifluoromethyl thiolsulphonates with a broad functional group tolerance. In the process, it is believed that sulfinate generated from sulfonyl chloride is a critical intermediate and the additive 4-methylbenzenesulfonic acid (p-TsOH) facilitates the formation of “CF3S+”. Electrophilic trifluoromethylthiolation of in situ generated sulfinate and “CF3S+” provides the final products. Graphical abstract image
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Sulfated polyborate catalyzed Kabachnik-Fields reaction: An efficient and eco-friendly protocol for synthesis of α-amino phosphonates ()
Publication date: 15 February 2017 Source:Tetrahedron Letters, Volume 58, Issue 7 Author(s): Chetan K. Khatri, Vardhan B. Satalkar, Ganesh U. Chaturbhuj An efficient, and environmentally benign protocol for a three-component Kabachnik-Fields reaction of aldehydes, amines, and diethyl phosphite catalyzed by sulfated polyborate has been described to afford α-amino phosphonates under solvent-free reaction conditions. The major advantages of the present method are high yields, short reaction time, simple work-up procedure, inexpensive, eco-friendly and reusable catalyst and solvent-free reaction conditions and tolerance towards various functional groups present in the substrates. Graphical abstract image
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Editorial board ()
Publication date: 8 February 2017 Source:Tetrahedron Letters, Volume 58, Issue 6
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Sulfonyl hydrazides as sulfonyl sources in organic synthesis ()
Publication date: 8 February 2017 Source:Tetrahedron Letters, Volume 58, Issue 6 Author(s): Fu-Lai Yang, Shi-Kai Tian While sulfonyl hydrazides are widely utilized in organic synthesis, it is only in recent years that they have emerged as powerful sulfonyl sources. The hydrazinyl group can be readily removed from sulfonyl hydrazides under thermal, basic, oxidative, radical, and/or transition metal-catalyzed conditions, and subsequently, the remaining sulfonyl groups are able to form carbon-sulfur, sulfur-nitrogen, sulfur-halogen, sulfur-sulfur, and sulfur-selenium bonds with a wide variety of organic compounds, providing alternative approaches to the preparation of sulfones, sulfonamides, sulfonyl halides, thiosulfonates, and selenosulfonates. Moreover, some of the carbon-sulfur bond-forming reactions have been successfully applied to the construction of carbocycles, heterocycles, and stereogenic centers. Graphical abstract image
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A highly selective colorimetric and fluorescent chemosensor for Cr2+ in aqueous solutions ()
Publication date: 8 February 2017 Source:Tetrahedron Letters, Volume 58, Issue 6 Author(s): J. Rull-Barrull, M. d'Halluin, E. Le Grognec, F.-X. Felpin A new rhodamine-based chemosensor was synthetized through a modified copper-catalyzed [3+2]-cycloaddition of an azidocoumarin with an alkynyl-rhodamine. Its sensing properties toward various metal cations in aqueous solutions were investigated by colorimetric changes, UV–vis and fluorescence spectroscopies. The sensor exhibited a high selectivity for Cr2+ over Cr3+ and other divalent cations such as Cu2+, Mg2+, Zn2+, Ca2+, Cd2+, Co2+, Hg2+ and Ni2+. The linear range of detection by fluorescence spectroscopy is 0.07–3.5mM, with a detection limit of ca. 64μM. The binding mode of Cr2+ with the sensor was rationalized through experimental evidences. Graphical abstract image
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First stereoselective total synthesis and reconfirmation of absolute structure of nonenolide (−)-stagonolide D ()
Publication date: 8 February 2017 Source:Tetrahedron Letters, Volume 58, Issue 6 Author(s): A. Sravanth Kumar, K. Praneeth, P. Srihari, J.S. Yadav The first stereoselective total synthesis of nonenolide (−)-stagonolide D has been accomplished. Midland Alpine borane reduction to install hydroxyl group at C4, Henbest epoxidation to introduce epoxide stereoselectively between C7 and C8, Yamaguchi esterification and Olefin metathesis reaction are the key steps involved in the total synthesis. Graphical abstract image
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New tetrahedral boron heterobicycles: Cyclocondensation of phenylboronic acid with β-keto butanoic acid N-acyl hydrazones ()
Publication date: 8 February 2017 Source:Tetrahedron Letters, Volume 58, Issue 6 Author(s): Antigoni Kotali, Anna Maniadaki, Elvira Kotali, Philip A. Harris, Ewa Różycka-Sokołowska, Piotr Bałczewski, John A. Joule A series of 4-phenyl-2-aryl-8-methyl-6-oxo-7-phenylhydrazo-2H,4H,6H,7H,8H[1,3,4,2]-oxadiazaborolo[2,3-b][1,3,2]oxazaborines were prepared in high yields via the reaction of phenylboronic acid with various N-acylhydrazones of 3-keto-2-(2′-phenylhydrazono) butanoic acid in the presence of 4Å molecular sieves. These derivatives represent a novel class of zwitterionic, tetrahedral boron heterocycles. Single crystal X-ray analysis of a representative boron containing product is reported. Graphical abstract image
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Microwave assisted synthesis of 2,3-dihydro-4H-benzo[4,5]thiazolo[3,2-a]furo[2,3-d]pyrimidin-4-ones and 6,7-dihydro-5H-furo[2,3-d]thiazolo[3,2-a]pyrimidin-5-ones using Mn(OAc)3 ()
Publication date: 8 February 2017 Source:Tetrahedron Letters, Volume 58, Issue 6 Author(s): Aslı Ustalar, Mehmet Yilmaz 2-Hydroxy-4H-benzo[4,5]thiazolo[3,2-a]pyrimidin-4-one 2a and 7-hydroxy-5H-thiazolo[3,2-a]pyrimidin-5-one 2b, were obtained in high yields under mild conditions from the cyclization reactions of bis-(2,4,6-trichlorophenyl) malonate and 2-aminobenzothiazole or 2-aminothiazole, respectively. A new class of compounds, 2,3-dihydro-4H-benzo[4,5]thiazolo[3,2-a]furo[2,3-d]pyrimidin-4-ones and 6,7-dihydro-5H-furo[2,3-d]thiazolo[3,2-a]pyrimidin-5-ones, were synthesized via the microwave assisted radical addition of compounds 2a and 2b to various alkenes using manganese(III) acetate. A preliminary acetylcholine esterase (AchE) inhibition test of compound 4e showed excellent (92%) inhibitory potential, comparable with the standard drug Donapezil®. Graphical abstract image
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Direct oxidative cascade cyclisation of 2-aminobenzoic acid and arylaldehydes to aryl 4H-3,1-benzoxazin-4-ones with oxone ()
Publication date: 8 February 2017 Source:Tetrahedron Letters, Volume 58, Issue 6 Author(s): Sathishkumar Munusamy, Vivek Panyam Muralidharan, Sathiyanarayanan Kulathu Iyer This paper presents a methodology of oxidative cascade cyclisation of 2-aminobenzoic acids and arylaldehyde using I2 as a catalyst and an environmentally benign oxidant oxone. This method displays facile access to a diverse range of substituted aryl 4H-3,1-benzoxazin-4-ones. This synthetic methodology has many advantages such as: (1) easy availability of starting material, (2) transition metal-free condition (3) use of an environmentally benign oxidant. Graphical abstract image
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Synthesis of 2-phenyl pyridine derivatives from aryl ketones and 1,3-diaminopropane using palladium acetate as a catalyst ()
Publication date: 8 February 2017 Source:Tetrahedron Letters, Volume 58, Issue 6 Author(s): Shrikant M. Ghodse, Vikas N. Telvekar A simple and efficient method for the synthesis of 2-phenyl pyridine via cyclization of aryl ketone with 1,3-diaminopropane using palladium acetate is established. This method is mild, operationally simple, involves short reaction time and involves easy workup procedure to afford the corresponding 2-phenyl pyridines in moderate to good yield. Graphical abstract image
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Solvent free, palladium catalyzed highly facile synthesis of diaryl disulfides from aryl thiols ()
Publication date: 8 February 2017 Source:Tetrahedron Letters, Volume 58, Issue 6 Author(s): Pratip Kumar Dutta, Arpi Majumder, Sanjay Dutta, Basab Bijayi Dhar, Parthapratim Munshi, Subhabrata Sen An efficient solvent free Pd(pCH2S)2dba catalyzed green-chemical strategy for the synthesis of diaryl disulfides from aryl thiols in moderate to excellent yield is reported. Variety of diaryl disulfides were synthesized. The catalyst is recyclable up to four cycles. Graphical abstract image
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Synthesis and properties of a thiophene-substituted diaza[7]helicene for application as a blue emitter in organic light-emitting diodes ()
Publication date: 8 February 2017 Source:Tetrahedron Letters, Volume 58, Issue 6 Author(s): Ting Chen, Baojie Zhang, Zhi Liu, Lian Duan, Guifang Dong, Ying Feng, Xinyu Luo, Deliang Cui Carbazole-based diaza[7]helicene substituted by thiophene groups, 2,12-dithiophene-5,15-dihexyl-5,15-diaza[7]helicene (6), was synthesised successfully and confirmed by 1H NMR, 13C NMR, High Resolution Mass Spectrometry, Time of Flight Mass Spectrometry. Compound 6 exhibited good solubility and excellent thermal stability with no melting point and a high decomposition temperature of 453.64°C. A doped device with a structure of ITO/NPB (50nm)/CBP: 10% 6 (30nm)/Bphen (20nm)/Mg:Ag (150nm)/Ag (50nm) emitted the blue light at 460nm with Commission Internationale de LEclairage (CIE) coordinate of (0.176, 0.26). The maximum brightness and external quantum efficiency (EQE) were 2306cdm−2 and 0.41%, respectively. Graphical abstract image
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Synthesis of substituted benzofurans and indoles by Zn-catalyzed tandem Sonogashira-cyclization strategy ()
Publication date: 8 February 2017 Source:Tetrahedron Letters, Volume 58, Issue 6 Author(s): Amrutha P. Thankachan, Kallikkakam S. Sindhu, Sankuviruthiyil M. Ujwaldev, Gopinathan Anilkumar Transition metal catalyzed cross-coupling reactions are one of the predominant strategies for the construction of heterocyclic structures which possess wide applications in the synthesis of natural products, pharmaceuticals, polymers, etc. Due to the vast importance of substituted benzofurans and indoles, numerous synthetic methodologies have been introduced for their synthesis. Among these methods, transition metal catalyzed cyclization reactions possess a unique position. In this manuscript, we disclose the first and efficient zinc-catalyzed protocol for the cyclization reactions of alkynes with 2-iodophenol and 2-iodoaniline leading to benzofurans and indoles respectively via a tandem Sonogashira coupling-cyclization process. Among the different metal catalysts, zinc has enormous potential due to its great availability, non-toxicity, eco-friendly and inexpensive nature. Zn(II) with N,N′-dimethylethylenediamine represents a suitable and efficient catalytic system for the desired tandem C C coupling-cyclization reactions, and a broad spectrum of functional groups are tolerated during the catalysis. A variety of substituted benzofurans and indoles have been successfully prepared in moderate to good yields under this new protocol. Graphical abstract image
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Base-controlled selective construction of polysubstituted dihydrofuran and furan derivatives through an I2-mediated cyclization ()
Publication date: 8 February 2017 Source:Tetrahedron Letters, Volume 58, Issue 6 Author(s): Chun-Bao Miao, Rui Liu, Yan-Fang Sun, Xiao-Qiang Sun, Hai-Tao Yang A base-controlled formal [3+2] cycloaddition of 1,3-dicarbonyl compounds to enones via an I2-mediated cyclization was reported. Highly functionalized dihydrofurans and furans were selectively obtained under I2/DMAP and I2/DBU conditions in the cyclization step, respectively. Graphical abstract image
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Novel synthesis of tetrahydro-1H-pyrrolo[1,2-a]imidazol-2-ones via decarboxylative cyclization reaction of α-amino acids and α-ketoamides ()
Publication date: 8 February 2017 Source:Tetrahedron Letters, Volume 58, Issue 6 Author(s): Jia-shou Wu, Hua-jiang Jiang, Jian-guo Yang, Zheng-neng Jin, Ding-ben Chen An efficient and practical method was developed for the synthesis of tetrahydro-1H-pyrrolo[1,2-a]imidazol-2-ones based on the decarboxylative cyclization reaction of α-ketoamides and proline. In most cases, tetrahydro-1H-pyrrolo[1,2-a]imidazol-2-ones were obtained with perfect diastereoselectivity to give trans-isomer in excellent yield. Graphical abstract image
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Visible light photoredox catalysis with N-hydroxyphthalimide for [4+2] cyclization between N-methylanilines and maleimides ()
Publication date: 8 February 2017 Source:Tetrahedron Letters, Volume 58, Issue 6 Author(s): Arvind K. Yadav, Lal Dhar S. Yadav An efficient [4+2] cyclization of N-methylanilines with maleimides to afford tetrahydroquinolines using N-hydroxyphthalimide as a metal-free and cheap organophotoredox catalyst is reported. The protocol involves C(sp3)H activation of N-methylanilines for the formation of α-amino radical without an oxidant at room temperature. The present method describes an easy preparation of tricyclic heterocycles in good to excellent yields under mild reaction conditions. Graphical abstract image
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Synthesis of proposed structure of rennellianone B: A study on rearrangement of anthraquinonyl propargyl ether toward 2H-pyranoanthraquinone ()
Publication date: 8 February 2017 Source:Tetrahedron Letters, Volume 58, Issue 6 Author(s): Young Taek Han Rennellianone B was originally reported as a natural 2H-pyranoanthraquinone, isolated from the root of Rennellia elliptica Korth. An efficient synthesis of the proposed structure of rennellianone B was accomplished, starting from alizarin. The key feature of the synthesis involves the Claisen rearrangement of the anthraquinonyl propargyl ether intermediate to provide a 2H-pyranoanthraquinone moiety. In addition, intensive studies on rearrangement reaction conditions of anthraquinonyl propargyl ether toward the 2H-pyranoanthraquinone skeleton were described. Graphical abstract image
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Stereoselective synthesis of N-benzyl conduramine F-1, N-benzyl ent-conduramine E-1, dihydroconduramine F-1 and ent-dihydroconduramine E-1 ()
Publication date: 8 February 2017 Source:Tetrahedron Letters, Volume 58, Issue 6 Author(s): Ramakrishna Katakam, Rajender Anugula, Lingamurthy Macha, Venkateswara Rao Batchu A short and stereoselective synthesis of conduramine F-1 and ent-conduramine E-1 derivatives have been achieved starting from d-mannitol using nucleophilic vinylation on imine. A concise sequence of vinylation at both ends of d-mannitol and followed by RCM allowed us to prepare target compound. Graphical abstract image
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Stereoselective synthesis of peracetylated (−)-gloeosporiol via acid catalysed intramolecular etherification ()
Publication date: 8 February 2017 Source:Tetrahedron Letters, Volume 58, Issue 6 Author(s): Aravind Reddy Dorigundla, Raju Gurrapu, Venkateswara Rao Batchu A simple and an efficient strategy have been developed for the stereoselective synthesis of peracetylated (−)-gloeosporiol by acid catalysed cyclisation from the commercially available starting materials. Graphical abstract image
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A new, convenient and expeditious synthesis of 4-alkyl-5-methyl-1H-pyrazol-3-ols in water through a multicomponent reaction ()
Publication date: 8 February 2017 Source:Tetrahedron Letters, Volume 58, Issue 6 Author(s): Subarna Jyoti Kalita, Rajarshi Bayan, Jutika Devi, Sanfaori Brahma, Hormi Mecadon, Dibakar Chandra Deka A new, simple and efficient synthesis of 4-alkyl-5-methyl-1H-pyrazol-3-ols in water by a two-pot four component reaction of ethyl acetoacetate, hydrazine hydrate, aldehyde and ketone in presence K2CO3 as the catalyst is described. Use of water as the reaction medium, operational simplicity, mild reaction conditions, application of a cost-effective, nontoxic and easily available catalyst with auto-tandem catalysis, wide substrate scope, easy workup and purification process make the protocol highly attractive. Graphical abstract image
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Hypervalent iodine (III)-mediated oxidation of aryl sulfonylhydrazones: A facile synthesis of N-aroyl-N′-acyl arylsulfonylhydrazides ()
Publication date: 8 February 2017 Source:Tetrahedron Letters, Volume 58, Issue 6 Author(s): E. Ramakrishna, Kapil Dev, Saransh Wales Maurya, Ibadur Rahman Siddiqui, Rakesh Maurya We have developed a novel and efficient method for the oxidation of aryl sulfonylhydrazones to N-aroyl-N′-acyl arylsulfonylhydrazides, using hypervalent iodine (III) reagent in good yields at room temperature. Graphical abstract image
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One-pot dichlorinative deamidation of primary β-ketoamides ()
Publication date: 8 February 2017 Source:Tetrahedron Letters, Volume 58, Issue 6 Author(s): Congke Zheng, Xiaohui Zhang, Muhammad Ijaz Hussain, Mingming Huang, Qing Liu, Yan Xiong, Xiangming Zhu An approach to the dichlorinative deamidation of primary β-ketoamides through ketonic cleavage is described, and a series of α,α-dichloroketones were furnished mostly in the presence of TEMPO. Based on control experiments, a mechanism involving tandem dichlorination and deamidation is proposed to interpret the observed reactivity. Graphical abstract image
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Synthesis of spiroindene-1,3-dione isothiazolines via a cascade michael/1,3-dipolar cycloaddition reaction of 1,3,4-oxathiazol-2-one and 2-arylidene-1,3-indandiones ()
Publication date: 8 February 2017 Source:Tetrahedron Letters, Volume 58, Issue 6 Author(s): Anjaiah Aitha, Satyanarayana Yennam, Manoranjan Behera, Jaya Shree Anireddy The reaction of 1,3,4-oxathiazol-2-one derivative with 2-arylidene-1,3-indandione to furnish novel spiroindene-1,3-dione isothiazoline derivatives by Michael/1,3-dipolar [3+2]-cycloaddition reaction was investigated. The key 1,3-dipolar cycloaddition reaction step was examined in toluene solvent at reflux temperature to obtain mixture of two regioisomers (6a and 6b – 14a and 14b) and single isomers (15–20). The scope of this new reaction was demonstrated with many examples with high reactivity and yields. Graphical abstract image
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A safe and selective method for reduction of 2-nitrophenylacetic acid systems to N-aryl hydroxamic acids using continuous flow hydrogenation ()
Publication date: 8 February 2017 Source:Tetrahedron Letters, Volume 58, Issue 6 Author(s): Ogar Ichire, Petra Jans, Galina Parfenov, Amy B. Dounay The cyclic hydroxamic acid functional group is critical to the biological activity of numerous natural products and drug candidates. Efficient, reliable, and green synthetic methods to produce cyclic hydroxamic acids are needed. Herein, flow hydrogenation has been explored as a novel approach toward achieving the selective partial reduction of 2-nitrophenylacetic acid to 1-hydroxyindolin-2-one. The bidentate ligand, 1,10-phenanthroline, has been identified as a unique inhibitor for modulating product selectivity in this Pt/C-catalyzed process. Under the newly optimized reaction conditions, the targeted hydroxamic acid is produced with high selectivity (49:1) over the lactam by-product. The scope of the reaction is demonstrated for a variety of 2-nitrophenylacetic acid derivatives. Graphical abstract image
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Copper-catalyzed chemoselective cross-coupling reaction of thioamides and α-diazocarbonyl compounds: Synthesis of enaminones ()
Publication date: 8 February 2017 Source:Tetrahedron Letters, Volume 58, Issue 6 Author(s): Arpal Pal, Naga D. Koduri, Zhiguo Wang, Erika Lopez Quiroz, Alexandra Chong, Matthew Vuong, Nisha Rajagopal, Michael Nguyen, Kenneth P. Roberts, Syed R. Hussaini The development of operationally simple and cost-effective methods for CC bond formation reactions are highly important in pharmaceutical, agrochemical and material research. In this article we describe the first copper-catalyzed cross-coupling reaction of thioamides with acceptor/acceptor-substituted and acceptor-only substituted α-diazocarbonyl compounds to yield enaminones. The reaction shows broad substrate scope in terms of thioamides and diazocarbonyl compounds. Primary, secondary and tertiary thioamides all give enanminones when reacted with α-diazodiesters, α-diazoketoesters, α-diazodiketones, α-diazoketoamides, α-diazoesteramides, α-diazoketosulfones and α-diazomonoketones. Graphical abstract image
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Cu2O spheres as an efficient source of catalytic Cu(I) species for performing azide-alkyne click reactions ()
Publication date: 8 February 2017 Source:Tetrahedron Letters, Volume 58, Issue 6 Author(s): Thenner S. Rodrigues, Anderson G.M. da Silva, Lucas C. de Oliveira, Adalberto M. da Silva, Róbson R. Teixeira, Pedro H.C. Camargo We report herein the high yield synthesis of Cu2O spheres displaying well-defined shapes and monodisperse sizes that could be employed as the source of highly catalytic active Cu(I) species towards click reactions between several of alkynes and azides to produce a variety of 1,2,3-triazoles under ligand-free and ambient conditions (in an open reactor). The utilization of Cu2O spheres enabled superior performance as compared to a conventional protocol in which CuSO4 is employed in combination with sodium ascorbate as the catalyst system. In addition, the compounds were obtained in synthetically useful yields, and seven of them have not been previously reported. We believe the results reported herein shed new insights into the optimization of activity and versatility of click reactions towards the synthesis of target molecules in environmentally friendly conditions. Graphical abstract image
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Editorial board ()
Publication date: 1 February 2017 Source:Tetrahedron Letters, Volume 58, Issue 5
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