Tetrahedron Letters

Editorial board ()
Publication date: 15 April 2015 Source:Tetrahedron Letters, Volume 56, Issue 16
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Graphical Contents List ()
Publication date: 15 April 2015 Source:Tetrahedron Letters, Volume 56, Issue 16
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Design of supramolecular chiral ligands for asymmetric metal catalysis ()
Publication date: 15 April 2015 Source:Tetrahedron Letters, Volume 56, Issue 16 Author(s): Kohsuke Ohmatsu , Takashi Ooi Three strategies for the development of supramolecular chiral ligands for asymmetric metal catalysis are outlined. The basic ideas, advantages, and examples of each strategy are described. Graphical abstract image
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Synthesis and spectral properties of phthalocyanine–BODIPY conjugates ()
Publication date: 15 April 2015 Source:Tetrahedron Letters, Volume 56, Issue 16 Author(s): Samira Osati , Hasrat Ali , Johan E. van Lier Various zinc phthalocyanines were substituted at ortho or meta positions with 1,3,5,7-tetramethyl-8-phenyl-4,4-difluoroboradiazaindacene (BODIPY) moieties via Pd catalyzed Sonogashira-coupling reactions, at either meso or β positions of the BODIPY. UV–Vis and fluorescence emission spectra of the conjugates exhibit panchromatic behavior due to their absorption over a broad spectral region from ultraviolet to visible and energy transfer from the excited BODIPY substituent to the phthalocyanine core. Some conjugates show red-shifted Q-bands that correlate to the planarity and dihedral angle between the subunits, as well as the position and number of attached BODIPY and phthalocyanine moieties. Graphical abstract image
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Intramolecular sulfonylamidomethylation of 2-(2-naphthyl) and 2-(1-naphthyl)ethanesulfonamides: synthesis of new class of naphthosultams ()
Publication date: 15 April 2015 Source:Tetrahedron Letters, Volume 56, Issue 16 Author(s): Leandro D. Sasiambarrena , Alicia S. Cánepa , Constanza N. Luna , Rodolfo D. Bravo New 1,2,4,5-tetrahydronaphtho[1,2-d]3,2-thiazepine 3,3-dioxides and 1,2,4,5-tetrahydronaphtho[2,1-d]3,4-thiazepine 3,3-dioxides were synthesized by aromatic intramolecular sulfonylamidomethylation of 2-(2-naphthyl) and 2-(1-naphthyl)ethanesulfonamides with s-trioxane using Amberlyst XN-1010 as catalyst in excellent yields and with high regioselectivity. Graphical abstract image
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Synthesis of N-alkylsulfonamides by borane–dimethyl sulfide reduction of N-acylsulfonamides ()
Publication date: 15 April 2015 Source:Tetrahedron Letters, Volume 56, Issue 16 Author(s): Samantha N. James , Mark J. Coster A convenient synthesis of N-alkylsulfonamides in good to excellent yields by reduction of N-acylsulfonamides using BH3·SMe2 is described. This methodology presents an attractive alternative for sulfonamide formation. Graphical abstract image
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Reduction of amide carbonyl group and formation of modified amino acids and dipeptides ()
Publication date: 15 April 2015 Source:Tetrahedron Letters, Volume 56, Issue 16 Author(s): M.L. Di Gioia , E.L. Belsito , A. Leggio , V. Leotta , E. Romio , C. Siciliano , A. Liguori An expeditious, practical, and mild method for the reduction of amides to amines is reported. The procedure is based on the activation of amides with titanium tetrachloride followed by reduction with lithium aluminum hydride. The reducing system can be applied to the reduction of tertiary and secondary amides giving the corresponding amines in good yields. The protocol was also extended to the reduction of amides of Nα-protected amino acid and dipeptides. The corresponding 1,2 diamines and diaminoalcohols were produced in high yields and with retention of configuration at the chiral centers. Graphical abstract image
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A convenient protocol for the deprotection of N-benzyloxycarbonyl (Cbz) and benzyl ester groups ()
Publication date: 15 April 2015 Source:Tetrahedron Letters, Volume 56, Issue 16 Author(s): Prakash R. Sultane , Trimbak B. Mete , Ramakrishna G. Bhat We describe a convenient and practical method for the deprotection of N-benzyloxycarbonyl (Cbz) and benzyl ester groups using NaBH4 and catalytic Pd–C in methanol. Deprotection was very facile and rapid. In situ generation of hydrogen is certainly user friendly and avoids the use of a hydrogen cylinder. In order to establish the wider applicability of this approach, deprotection has also been demonstrated in gram scale reactions. Graphical abstract image
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Investigation on the asymmetric addition reactions between varied nonaromatic aldehydes and diethylzinc catalyzed by chiral phosphoramide and thiophosphorodiamide ligands ()
Publication date: 15 April 2015 Source:Tetrahedron Letters, Volume 56, Issue 16 Author(s): Fangling Li , Huayin Huang , Hua Zong , Guangling Bian , Ling Song The asymmetric addition reactions between varied nonaromatic aldehydes and diethylzinc catalyzed by chiral phosphoramide L1 and thiophosphorodiamide L4 were thoroughly investigated. Both ligands worked very well for α-branched aliphatic and α-branched α,β-unsaturated aldehydes. For α-nonbranched aliphatic aldehydes, L4 behaved much better than L1 . For α-nonbranched α,β-unsaturated aldehydes, L4 showed high enantioselectivities and L1 only gave racemic alcohol products. Graphical abstract image
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Direct synthesis of 2-arylbenzothiazoles from benzothiazoles with phenylglycine derivatives mediated by Cu(OTf)2/K2S2O8 ()
Publication date: 15 April 2015 Source:Tetrahedron Letters, Volume 56, Issue 16 Author(s): Rui Wang , Chun-hong An , Yang Li , Yue Zhao , Tao Wang , Ao Li A new approach to the construction of 2-arylbenzothiazole through the direct oxidative coupling from benzothiazoles and phenylglycine derivatives is disclosed. The method which mediated by Cu(OTf)2/K2S2O8 system affords a variety of useful substituted 2-arylbenzothiazole derivatives in an efficient and practical manner. Graphical abstract image
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Facile synthesis of 3-aldehyde-2-substituted thiophenes through Lewis base catalyzed [3+2] cycloaddition of 1,4-dithiane-2,5-diols with ynals ()
Publication date: 15 April 2015 Source:Tetrahedron Letters, Volume 56, Issue 16 Author(s): Wenjuan Shi , Li Wan , Yimin Hu , Shaofa Sun , Wenjun Li , Yanhong Peng , Minghu Wu , Haibing Guo , Jian Wang Et3N-catalyzed [3+2] cycloaddition of 1,4-dithiane-2,5-diol with ynal has been developed. This strategy provides a rapid way to synthesize 3-aldehyde-2-substituted thiophene in one portion and the desired products could be obtained in high yields, which contain various functional groups. Graphical abstract image
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Synthesis of hexabenzocoronene-layered compounds ()
Publication date: 15 April 2015 Source:Tetrahedron Letters, Volume 56, Issue 16 Author(s): Tatsuya Nakano , Yasuhiro Morisaki , Yoshiki Chujo We report herein the synthesis and properties of π-stacked dimeric and polymeric compounds that consisted of hexabenzocoronene (HBC) and xanthene as the stacked π-electron system and the scaffold, respectively; the compounds were obtained by Sonogashira–Hagihara coupling. The obtained polymer was separated into three fractions, and the through-space conjugation effect was estimated. HBC units were layered in proximity (approximately 3.4Å), leading to π–π stacking in the ground and excited states. Graphical abstract image
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An Ag2O-responsive [2]pseudorotaxane based on the pillar[5]arene/bis(imidazolium) dication molecular recognition motif ()
Publication date: 15 April 2015 Source:Tetrahedron Letters, Volume 56, Issue 16 Author(s): Yujuan Zhou , Kecheng Jie , Connor Thompson , Ning Li , Yong Yao A pillar[5]arene-based [2]pseudorotaxane was successfully synthesized. The damage and re-formation of it could be controlled by adding Ag2O and CF3COOH, respectively. The special metalloresponsiveness makes this novel host–guest recognition motif have broad potential applications in a number of areas. Graphical abstract image
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α-Monoarylation and tandem arylation–insertion of malonates with arynes ()
Publication date: 15 April 2015 Source:Tetrahedron Letters, Volume 56, Issue 16 Author(s): Qian Chen , Changyuan Zhang , Lili Chen , Chunxiao Wen , Zhiyun Du , Huixiong Chen , Kun Zhang The efficient α-monoarylation and tandem arylation–insertion of malonates with arynes, generated by fluoride-induced elimination of Kobayashi’s silylaryl triflates, are described. The reactions led to the formation of α-arylmalonates in up to 88% yield with high chemoselectivities and diarylmethane derivatives in good yields under mild conditions. Graphical abstract image
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Tetrabutylammonium-assisted diastereoselective [6π]-photocyclization of acrylanilides ()
Publication date: 15 April 2015 Source:Tetrahedron Letters, Volume 56, Issue 16 Author(s): Shinji Yamada , Mai Okuda , Natsuo Yamamoto Tetrabutylammonium salts are remarkably effective for increasing diastereoselectivities in [6π]-photocyclization reactions of acrylanilides. This TBA+-assisted photocyclization is applicable to a variety of acrylanilides to afford trans-dihydroquinolones. Using a d 5-labeled substrate, it was elucidated that a tetrabutylammonium ion shields a zwitterionic intermediate from an intermolecular H-transfer, which enables preferential occurrence of the [1,5] H-shift to give trans products stereoselectively. Graphical abstract image
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Formal [3+3]-cycloaddition of 3-methyl-5,6-dihydro-4H-1,2-oxazine-N-oxides with cyclopropane dicarboxylates under hyperbaric conditions ()
Publication date: 15 April 2015 Source:Tetrahedron Letters, Volume 56, Issue 16 Author(s): Andrey A. Tabolin , Roman A. Novikov , Yulia A. Khomutova , Alexey A. Zharov , Galina A. Stashina , Yulia V. Nelyubina , Yury V. Tomilov , Sema L. Ioffe The [3+3]-cycloaddition of cyclopropane dicarboxylates with 3-methyl-5,6-dihydro-4H-1,2-oxazine-N-oxides promoted by Yb(OTf)3 under hyperbaric conditions is described. The substrates scope and reaction mechanism are discussed. Graphical abstract image
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A facile synthesis of steroidal and nonsteroidal pyrimidines under microwave irradiation ()
Publication date: 15 April 2015 Source:Tetrahedron Letters, Volume 56, Issue 16 Author(s): Pallabi Saikia , Sanjib Gogoi , Romesh C. Boruah The synthesis of steroid/nonsteroid fused pyrimidines is described by the base mediated reaction of steroidal/nonsteroidal α,β-unsaturated ketones with amidine derivatives in good yields under microwave irradiation. Graphical abstract image
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Total synthesis of (±)-γ-indomycinone ()
Publication date: 15 April 2015 Source:Tetrahedron Letters, Volume 56, Issue 16 Author(s): Mathilde Pantin , Doumadé Zon , Romy Vomiandry , Laura Foulgoc , Drissa Sissouma , André Guingant , Sylvain Collet The total synthesis of racemic γ-indomycinone has been achieved following an innovating convergent approach. The key step in the construction of the tetracyclic core corresponds to a Diels–Alder reaction between a substituted 5-isoprenyl-3,4-dihydro-2H-pyran and juglone as the dienophile. The used strategy can easily be transposed to the synthesis of (R)-γ-indomycinone starting from optically pure (2R)-2-benzyloxy-2-methylbutanal. Graphical abstract image
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Editorial board ()
Publication date: 8 April 2015 Source:Tetrahedron Letters, Volume 56, Issue 15
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Graphical Contents List ()
Publication date: 8 April 2015 Source:Tetrahedron Letters, Volume 56, Issue 15
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A new modification of the Passerini reaction: a one-pot synthesis of α-acyloxyamides via sequential Kornblum oxidation/Passerini reaction ()
Publication date: 8 April 2015 Source:Tetrahedron Letters, Volume 56, Issue 15 Author(s): Mehdi Adib , Ehsan Sheikhi , Marjan Azimzadeh A novel approach for the synthesis of α-acyloxyamides is described. Benzylic substrates (halides or tosylates), under mild Kornblum conditions, are oxidized to give the corresponding aldehydes, which undergo a Passerini reaction with carboxylic acids and isocyanides to produce the corresponding α-acyloxyamides in excellent yields. Graphical abstract image
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Novel ether and thioether macrocycles from phthalaldehyde ()
Publication date: 8 April 2015 Source:Tetrahedron Letters, Volume 56, Issue 15 Author(s): R. Alan Aitken , Clémence Hauduc , Ross S. McLennan , Alexandra M.Z. Slawin , Heather S. Wilson By reaction of phthalaldehyde (benzene-1,2-dicarbaldehyde) with ethane-1,2-diol or 2-mercaptoethanol, macrocycles containing respectively 14- and 12-membered polyether/thioether rings were obtained in low but reproducible yields, and their structures confirmed by X-ray diffraction. The simple compounds (2-vinylphenyl)oxirane and 2-oxiranylbenzaldehyde have also been prepared and characterised for the first time. Graphical abstract image
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Ritter reactions of isoflavanols: a facile route to 4-amidoisoflavans ()
Publication date: 8 April 2015 Source:Tetrahedron Letters, Volume 56, Issue 15 Author(s): George Iskander , Kasey Wood , Eleanor Eiffe , Eugene M.H. Yee , David StC. Black , Naresh Kumar A one-step procedure for the synthesis of 4-amidoisoflavans from isoflavanols is described. The synthetic protocol allows for the introduction of a variety of substituents to the isoflavan scaffold via an amide linker. Graphical abstract image
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Conversion of α,β-unsaturated ketones to 1,5-diones via tandem retro-Aldol and Michael addition using Co(acac)2 covalently anchored onto amine functionalized silica ()
Publication date: 8 April 2015 Source:Tetrahedron Letters, Volume 56, Issue 15 Author(s): Ravinderpal Kour Sodhi , Satya Paul , Vivek K. Gupta , Rajni Kant A new and efficient method has been developed for the conversion of α,β-unsaturated ketones to 1,5-diketones via tandem retro-Aldol and Michael addition in the presence of Co(acac)2 covalently anchored amine functionalized silica [AS-Co(acac)2]. The single crystal X-ray crystallography confirms the formation of 1,5-diketones. This method has been proved to be an attractive alternative to existing methodologies under conventional homogeneous catalysis with the frequent troublesome manipulation and work-up. The AS-Co(acac)2 was found to be highly active and could be recycled for four consecutive runs with slight decrease in activity. Graphical abstract image
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Preparation of tetrasubstituted pyrimido[4,5-d]pyrimidine diones ()
Publication date: 8 April 2015 Source:Tetrahedron Letters, Volume 56, Issue 15 Author(s): Hui Wang , Chao Wang , Thomas D. Bannister A novel synthetic route to 1,3,5,7-tetrasubstituted pyrimido[4,5-d]pyrimidine-2,4-diones, of interest for potential antitumor activity, is reported. The route uses 1,3-disubstituted 6-amino uracils as starting materials. The key step is a hydrazine-induced cyclization reaction to form the fused pyrimidine ring. By choosing different uracils, acylation reagents, and alkylation reagents, substituents at N-1, N-3, C-5, and C-7 may be selectively varied to provide a structurally diverse set of compounds for biological evaluation. Graphical abstract image
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Two new adamantyl-like polyprenylated acylphloroglucinols from Hypericum attenuatum choisy ()
Publication date: 8 April 2015 Source:Tetrahedron Letters, Volume 56, Issue 15 Author(s): Dongyan Li , Hucheng Zhu , Changxing Qi , Yongbo Xue , Guangmin Yao , Zengwei Luo , Jianping Wang , Jinwen Zhang , Guang Du , Yonghui Zhang Two new adamantyl-like polyprenylated acylphloroglucinols, hyperattenins J (1) and K (2), were isolated from the aerial parts of Hypericum attenuatum choisy. Their structures and absolute configurations were elucidated by rigorous spectroscopic analyses including NMR, HRESIMS, and electronic circular dichroism (ECD). Hyperattenin J (1) features by a unique furan-fused adamantyl core structure with an unusual hemiacetal group. Hyperattenin K (2) exhibited inhibitory effects on HIV-1 replication in C8166 cells and moderate cytotoxicity against the HL-60 and A-549 cell lines. The possible biogenetic pathway of 1 is also discussed. Graphical abstract image
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Hydroxy group directed stereochemistry in oxypalladation of chiral allylic alcohol ()
Publication date: 8 April 2015 Source:Tetrahedron Letters, Volume 56, Issue 15 Author(s): Akiko Ida , Kazuyuki Kitao , Naoyuki Hoshiya , Jun’ichi Uenishi Stereochemistry of oxypalladation for ε-hydroxy chiral allylic alcohol is described. anti- and syn-face selective syn-oxypalladation to a chiral allyl alcohol takes place and provides enantiomerically opposite 2-(Z)-alkenyl and 2-(E)-alkenyl substituted oxacyclic rings in a ratio of 2:3. Graphical abstract image
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s-Triazene based fluorous coupling reagent for direct amide synthesis ()
Publication date: 8 April 2015 Source:Tetrahedron Letters, Volume 56, Issue 15 Author(s): Shrawan Kumar Mangawa , Sangram Keshari Bagh , Kumkum Sharma , Satish K. Awasthi A new simple and efficient fluorous coupling reagent TriTFET (2,4,6-tris-(2,2,2-trifluoro-ethoxy)-[1,3,5] triazene) has been designed and synthesized for the direct amidation. The use of 5mol% of TriTFET is good for the amide synthesis from carboxylic acids with amines in moderate to excellent yields (72–96%). Graphical abstract image
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Sonogashira coupling and Garratt–Braverman cyclization in tandem: formation of four C–C bonds leading to the synthesis of aryl dihydro isofurans and isoindoles ()
Publication date: 8 April 2015 Source:Tetrahedron Letters, Volume 56, Issue 15 Author(s): Debaki Ghosh , Paramita Pal , Amit Basak In this Letter we report an interesting one pot synthesis of aryl dihydro isofurans and isoindoles, naturally occurring privileged skeletons, in excellent yields from easily accessible starting materials. The process involved carrying out three reactions in a tandem manner leading to 4 C–C bond formations, namely two Sonogashira couplings (2×1 C–C bond) followed by Garratt–Braverman Cyclization (2 C–C bond). Graphical abstract image
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Copper on chitosan: an efficient and easily recoverable heterogeneous catalyst for one pot synthesis of 1,2,3-triazoles from aryl boronic acids in water at room temperature ()
Publication date: 8 April 2015 Source:Tetrahedron Letters, Volume 56, Issue 15 Author(s): B.S.P. Anil Kumar , K. Harsha Vardhan Reddy , K. Karnakar , G. Satish , Y.V.D. Nageswar A facile, efficient, and environmentally-friendly one pot protocol has been developed for the synthesis of 1,4-diaryl-1,2,3-triazoles from boronic acids, sodium azide, and acetylenes using copper sulfate immobilized on chitosan as a recyclable heterogeneous catalyst. This green synthetic three component protocol avoids handling of hazardous and toxic azides involving its in situ generation. The use of aqueous medium at room temperature and the easy recovery of the catalyst are other remarkable features of this procedure. Graphical abstract image
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Facile and efficient synthesis of hydroxyalkyl esters from cyclic acetals through aerobic photo-oxidation using anthraquinone-2-carboxylic acid ()
Publication date: 8 April 2015 Source:Tetrahedron Letters, Volume 56, Issue 15 Author(s): Tomoaki Yamaguchi , Yasuhisa Kudo , Shin-ichi Hirashima , Eiji Yamaguchi , Norihiro Tada , Tsuyoshi Miura , Akichika Itoh A convenient metal-free oxidation protocol of various cyclic acetals with molecular oxygen and anthraquinone-2-carboxylic acid under visible light irradiation by a fluorescent lamp afforded their corresponding hydroxyalkyl esters. Graphical abstract image
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Urea treated subtilisin as a biocatalyst for transformations in organic solvents ()
Publication date: 8 April 2015 Source:Tetrahedron Letters, Volume 56, Issue 15 Author(s): Joyeeta Mukherjee , Prasant Mishra , Munishwar N. Gupta Subtilisin lyophilized from its solution in aqueous buffer in the presence of 6M urea showed up to 50-fold increase (as compared to lyophilized subtilisin not subjected to urea treatment) in its initial rate of a transesterification reaction in anhydrous n-hexane. The lyophilization time controlling the extent of ‘drying’ was an important parameter. The urea treated subtilisin had five times shorter half life during heating at 100°C in hexane. The change in conformation was also reflected in its 92-fold higher activity at 15°C as compared to merely 28-fold higher activity at 45°C. The comparative enantioselectivity of urea treated subtilisin during kinetic resolution of 1-phenylethanol was expectedly lower. Its enantioselectivity during kinetic resolution of a natural substrate N-acetyl-(R,S)-phenylalanine ethyl ester in hexane was higher. Urea treated subtilisin also showed higher catalytic promiscuity during an aldol condensation. CD studies in both far UV and near UV region were also carried out to compare the two structures. Graphical abstract image
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Oxidative dearomatization and unusual intramolecular Diels–Alder reaction of cyclohexa-2,4-dienone: synthesis and photoreaction of oxa-tricyclo[5.2.2.01,5]undec-10-ene-8-ones ()
Publication date: 8 April 2015 Source:Tetrahedron Letters, Volume 56, Issue 15 Author(s): Vishwakarma Singh , Beauty Das An efficient synthesis of annulated bicyclo[2.2.2]octane having β,γ-enone chromophoric system and triplet sensitized 1,2-acyl shift rearrangement leading to the formation of angular oxa-triquinane is described. Oxidative dearomatization, intramolecular Diels–Alder reaction of 6,6-spiroepoxycyclohexa-2,4-dienone and oxa-di-π-methane reaction are the key features of our approach. Graphical abstract image
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Synthesis and antiviral activity of anthracene derivatives of isoxazolino-carbocyclic nucleoside analogues ()
Publication date: 8 April 2015 Source:Tetrahedron Letters, Volume 56, Issue 15 Author(s): Misal Giuseppe Memeo , Francesco Lapolla , Giovanni Maga , Paolo Quadrelli Isoxazolino-carbocyclic anthracene nor-nucleosides were prepared through nitrosocarbonyl chemistry and tested for their inhibitory activity against some viruses, such as Herpes simplex viruses of type 1 and 2, Zoster virus and Hepatitis B and C. The activities were almost negligible in most of the cases. A remarkable antiviral activity was found for a specific regioisomer with no cellular toxicity at 1–100μM dose concentration in the case of Human Papilloma virus. Graphical abstract image
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Visible light sensitized isomerization of rhodopsin-based molecular switches ()
Publication date: 8 April 2015 Source:Tetrahedron Letters, Volume 56, Issue 15 Author(s): David Martínez-López , Marina Blanco-Lomas , Pedro J. Campos , Diego Sampedro Neutral rhodopsin-based molecular photoswitches can be activated by using low-energy visible light through sensitized irradiation. The triplet state of the neutral and protonated forms are studied and compared by the use of different experimental conditions, laser flash photolysis, and theoretical calculations. The use of common, visible light absorbing sensitizers allows for the photoisomerization without the requirement of acidic water solutions. Graphical abstract image
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Synthesis of phosphonic analogues of AAZTA†AAZTA=6-Amino-6-methylperhydro-1,4-diazepine-N,N′,N″,N″-tetraacetic acid.† and relaxometric evaluation of the corresponding Gd(III) complexes as potential MRI contrast agents ()
Publication date: 8 April 2015 Source:Tetrahedron Letters, Volume 56, Issue 15 Author(s): Claudia Guanci , Roberta Pinalli , Silvio Aime , Eliana Gianolio , Luciano Lattuada , Giovanni B. Giovenzana AAZTA was developed in the last decade as an efficient chelating agent for lanthanides and other metal ions of diagnostic and therapeutic interest. Different derivatives of AAZTA were designed and synthesized in order to modulate the physico-chemical properties of the corresponding chelates or to conjugate them to carrier molecules for molecular imaging applications. In this work, three different analogues of AAZTA bearing one or two phosphonic acid residues were synthesized in three step procedures and moderate to good yields. The effects of this isofunctional substitution on the structure and properties of the corresponding Gd(III) complexes were preliminarily investigated by relaxometric techniques. The presence of phosphonic groups progressively reduces the number of coordinated water molecules on the metal center and increases the second-sphere contribution to the relaxivity. Graphical abstract image
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One-pot fluorination and Mannich reactions of 1,3-dicarbonyl compounds ()
Publication date: 8 April 2015 Source:Tetrahedron Letters, Volume 56, Issue 15 Author(s): Kenny Pham , Xin Huang , Wei Zhang One-pot fluorination of 1,3-dicarbonyl compounds with Selectfluor™ followed by the Mannich reaction with anilines and benzaldehydes is developed for the synthesis of α-fluoro and aminomethylated 1,3-dicarbonyl compounds. Graphical abstract image
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Synthesis of pyridinium salts from N-substituted dihydropyridines with BF3OEt2 in the absence of added oxidants ()
Publication date: 8 April 2015 Source:Tetrahedron Letters, Volume 56, Issue 15 Author(s): Lais D. Guanaes , Diogo R.B. Ducatti , M. Eugênia R. Duarte , Sandra M.W. Barreira , Miguel D. Noseda , Alan G. Gonçalves N-Substituted dihydropyridines were converted into pyridinium salts with BF3OEt2 as aromatization promoter in reactions that could be conducted without the need of the usually added oxidizing agents, such as quinones, nitrates, peroxides, and chromates. An optimization study employing an N-phenyl Hantzsch ester dihydropyridine (1a) to obtain the corresponding N-phenylpyridinium-containing ammonium quaternary salt (2a) was conducted to define the best conditions for the aromatization reaction: 3equiv of BF3OEt2 at 0°C, in the dark, under atmospheric air in CH2Cl2 to give yields up to 80%. These conditions could also be applied to additional examples of both N-substituted dihydropyridines and 1,4-dihydropyridines. Graphical abstract image
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Cobalt(I)-сatalyzed [6π+2π]-сycloadditions of 1,2-dienes to 1,3,5,7-cyclooctatetraene ()
Publication date: 8 April 2015 Source:Tetrahedron Letters, Volume 56, Issue 15 Author(s): Vladimir A. D’yakonov , Gulnara N. Kadikova , Guzel F. Gazizullina , Leonard M. Khalilov , Usein M. Dzhemilev The reaction between 1,2-dienes and 1,3,5,7-cyclooctatetraene in the presence of the multicomponent catalyst, CoI2/dppe/Zn/ZnI2 leads to the selective formation of (E)-bicyclo[4.2.2]deca-2,4,7-triene derivatives in yields of 65–85%. Graphical abstract image
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A highly regio- and stereoselective Pd-catalyzed tandem allylic rearrangement/intramolecular decarboxylative coupling of aryl propiolates derived from Baylis–Hillman adducts ()
Publication date: 8 April 2015 Source:Tetrahedron Letters, Volume 56, Issue 15 Author(s): Tummanapalli Satyanarayana , Dhanunjaya Naidu Vangapandu , Parthasarathy Muthuraman , Shashidhar Nizalapur A highly regio- and stereoselective Pd-catalyzed tandem allylic rearrangement/intramolecular decarboxylative coupling of aryl propiolates derived from Baylis–Hillman alcohols leading to the formation of an important class of 1,5-diarylpent-1-en-4-ynes has been developed. The aryl propiolates of Baylis–Hillman alcohols derived from methyl acrylate provided exclusively (E)-1,5-diarylpent-1-en-4-ynes while the aryl propiolates of Baylis–Hillman alcohols derived from acrylonitrile provided exclusively (Z)-1,5-diarylpent-1-en-4-ynes. Graphical abstract image
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An optimized and scalable synthesis of propylphosphonic anhydride for general use ()
Publication date: 8 April 2015 Source:Tetrahedron Letters, Volume 56, Issue 15 Author(s): Hana Pizova , Pavel Bobal Propylphosphonic anhydride (T3P®) is an effective coupling and dehydrating agent, which has been used for a large number of chemical transformations. An efficient and versatile synthetic method is described to synthesize propylphosphonic anhydride (T3P®) in pure form, in an overall yield of 51% in four steps from commercially available diethyl phosphonate. Graphical abstract image
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Approaches towards the total synthesis of carolacton: synthesis of C1–C16 fragment ()
Publication date: 8 April 2015 Source:Tetrahedron Letters, Volume 56, Issue 15 Author(s): Sheri Venkata Reddy , K. Prasanna Kumar , Kallaganti V.S. Ramakrishna , Gangavaram V.M. Sharma A stereoselective synthesis of the C1–C16 segment of biofilm inhibitor carolacton has been achieved. The synthetic strategy involves Sharpless asymmetric epoxidation, Roush crotylation, Steglich esterification, RCM reaction and selective reduction of a disubstituted olefin in the presence of a trisubstituted olefin using in situ generated diimide. Graphical abstract image
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Proline catalyzed, one-pot three component Mannich reaction and sequential cyclization toward the synthesis of 2-substituted piperidine and pyrrolidine alkaloids ()
Publication date: 8 April 2015 Source:Tetrahedron Letters, Volume 56, Issue 15 Author(s): Shibin Chacko , Ramesh Ramapanicker A very effective one-pot three component reaction of 4-bromobutanal or 5-bromopentanal, acetone, and p-anisidine catalyzed by proline is reported. A three component Mannich reaction followed by cyclization leading to the synthesis of 2-substituted pyrrolidine and piperidine derivatives through simultaneous formation of two C–N and one C–C bond is reported. The usefulness of the reaction is demonstrated by the synthesis of (±)coniine, (±)pelletrine, (±)sedridine, and (±)allosedridine. Graphical abstract image
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A novel approach to ortho-carborane by decarboranylation of 1-(isopropyl benzoate)-1,2-dicarba-closo-dodecaborane ()
Publication date: 8 April 2015 Source:Tetrahedron Letters, Volume 56, Issue 15 Author(s): Chen Feng , Haicheng Zhang , Jiping Yang , Gong Chen A novel approach was successfully developed for the synthesis of ortho-carborane [1,2-dicarba-closo-dodecaborane(12)] by reaction of 1-(isopropyl benzoate)-1,2-dicarba-closo-dodecaborane with KOH in methanol at 20°C. A decarboranylation in base of the first formed alcoholysis intermediate product 1-(2-propanol)-1,2-dicarba-closo-dodecaborane was suggested for this process. Graphical abstract image
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Rapid structural diversification of pseudopterosins: sulfuric acid promoted dehydro-aromatization yielding 14,15-dihydro-elisabatin B ()
Publication date: 8 April 2015 Source:Tetrahedron Letters, Volume 56, Issue 15 Author(s): Malcolm W.B. McCulloch , Russell G. Kerr Herein, we report a one-pot, sulfuric acid promoted, dehydro-aromatization reaction to rapidly convert pseudopterosins into 14,15-dihydro-elisabatin B. We propose a mechanism invoking redox cycling between the substrate catechol and ortho-quinone moieties. We also provide full spectroscopic characterization of two novel 5,6-dihydro-1H-phenalen-2(4H)-one derivatives, which are minor products of the reaction. This work opens up a unique route to rapidly provide libraries of novel marine natural product derivatives for drug discovery. Graphical abstract image
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Corrigendum to “Synthesis of unnatural 2- and 3-deoxyfuranose analogues” [Tetrahedron Lett. 55 (2014) 3706–3708] ()
Publication date: 8 April 2015 Source:Tetrahedron Letters, Volume 56, Issue 15 Author(s): Bénédicte Dayde , Claire Pierra , Gilles Gosselin , Dominique Surleraux , Daniel Da Costa , Amadou Tidjani Ilagouma , Arie Van der Lee , Jean-Noël Volle , David Virieux , Jean-Luc Pirat
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Corrigendum to “Synthesis of unnatural 3′-phospha-2′-deoxyfuranose nucleoside analogues” [Tetrahedron Lett. 55 (2014) 6328–6330] ()
Publication date: 8 April 2015 Source:Tetrahedron Letters, Volume 56, Issue 15 Author(s): Bénédicte Dayde , Claire Pierra , Gilles Gosselin , Dominique Surleraux , Daniel Da Costa , Amadou Tidjani Ilagouma , Jean-Noël Volle , David Virieux , Jean-Luc Pirat
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Editorial board ()
Publication date: 1 April 2015 Source:Tetrahedron Letters, Volume 56, Issue 14
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Graphical Contents List ()
Publication date: 1 April 2015 Source:Tetrahedron Letters, Volume 56, Issue 14
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Catalytic asymmetric synthesis of planar-chiral transition-metal complexes ()
Publication date: 1 April 2015 Source:Tetrahedron Letters, Volume 56, Issue 14 Author(s): Sachie Arae , Masamichi Ogasawara Planar-chiral transition-metal complexes are important chiral scaffolds in organic and organometallic chemistry and have been utilized as chiral ligands, chiral catalysts, or chiral building blocks. In spite of the usefulness of planar-chiral transition-metal complexes in asymmetric synthesis, enantiomerically enriched forms of these compounds are primarily obtained by rather classical methods. Examples of catalytic controlling planar-chirality in transition-metal species have been extremely rare, and this has been still a developing area in this field. In this review article, various methods of preparing enantiomerically enriched planar-chiral transition-metal complexes using substoichiometric chiral sources are surveyed. Most of the asymmetric reactions in these categories are transition-metal-catalyzed reactions, and there are a few examples of organocatalytic reactions. Graphical abstract image
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