Tetrahedron Letters

Editorial board ()
Publication date: 26 August 2015 Source:Tetrahedron Letters, Volume 56, Issue 35
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Graphical Contents List ()
Publication date: 26 August 2015 Source:Tetrahedron Letters, Volume 56, Issue 35
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Synthesis of carbohydrate-conjugated azaphthalocyanine complexes for PDT ()
Publication date: 26 August 2015 Source:Tetrahedron Letters, Volume 56, Issue 35 Author(s): Jong Min Park, Cheol Jun Song, Wang Yao, Chang Young Jung, In Ho Hyun, Dong Hoon Seong, Jae Yun Jaung A series of azaphthalocyanine (AzaPc) complexes conjugated with one or two carbohydrate groups for photodynamic therapy (PDT) were synthesized by the alkyne–azide click chemistry reaction with previously-developed AzaPc complexes incorporating the bornane group. Graphical abstract image
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Synthesis of 3,3-dichloro-2-oxindoles from isatin-3-p-tosylhydrazones and (dichloroiodo)benzene ()
Publication date: 26 August 2015 Source:Tetrahedron Letters, Volume 56, Issue 35 Author(s): Charlotte Hepples, Graham K. Murphy A series of aryl- and N-substituted isatin derivatives were converted to the corresponding isatin-3-p-tosylhydrazones, and these were subjected to a Lewis base-catalyzed chlorination reaction that employs the hypervalent chlorinating agent PhICl2. The discovery of p-tosylhydrazones as chlorination precursors has expanded the functional group tolerance of the chlorination reaction to now include carbamates, acetamides, and sulfonates. Additionally, this allowed us to circumvent the use of the diazo group in our chlorination reaction, and offers a new avenue for exploring our two-step deoxygenative dihalogenation reaction. We also disclose the use of PhICl2 for the oxidative chlorination of sulfinates to the corresponding sulfonyl chlorides. Graphical abstract image
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Turn-on fluorescent probe designed for fluoride ion sensing in aqueous media ()
Publication date: 26 August 2015 Source:Tetrahedron Letters, Volume 56, Issue 35 Author(s): Arundhati Roy, Tanmoy Saha, Pinaki Talukdar A NBD-based probe for selective detection of fluoride ion in aqueous media is reported. The probe was designed by applying rules for water solubility and membrane permeability. The probe functions through the fluoride mediated cascade reaction which was studied by 1H NMR, HPLC analysis, UV–vis, and fluorescence spectroscopy. The sensing process was marked by a colour change from colourless to yellow, and an intriguing 120-fold turn-on green fluorescence. Application of the probe for selective detection of fluoride was demonstrated by live-cell imaging. Graphical abstract image
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Synthesis of benzoxepinopyrrolidines/spiropyrrolidines via oxa-Pictet–Spengler and [3+2] cycloaddition reactions ()
Publication date: 26 August 2015 Source:Tetrahedron Letters, Volume 56, Issue 35 Author(s): Manickam Bakthadoss, Nagappan Sivakumar, Anthonisamy Devaraj A convenient one-pot synthesis of 2-benzoxepines generated from (E)-2-nitro-3-arylprop-2-en-1-ols with paraformaldehyde via oxa-Pictet–Spengler cyclization is described. Furthermore, the 1,3-dipolar cycloaddition of 2-benzoxepines with azomethine ylides using isatin/paraformaldehyde led to the formation of tricyclic benzoxepinopyrrolidine and pentacyclic benzoxepinospiropyrrolidine oxindole architectures for the first time. Graphical abstract image
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Chitosan: highly efficient, green, and reusable biopolymer catalyst for the synthesis of alkylaminophenols via Petasis borono–Mannich reaction ()
Publication date: 26 August 2015 Source:Tetrahedron Letters, Volume 56, Issue 35 Author(s): Sirigi Reddy Sudharsan Reddy, Bhoomireddy Rajendra Prasad Reddy, Peddiahgari Vasu Govardhana Reddy We screened the catalytic efficacy of different functionalized polymeric catalysts such as nafion® 117, PEG-OSO3H, tween® 80, poly styrene –SO3H and chitosan for the preparation of alkylaminophenols through Petasis borono–Mannich reaction by one-pot three component condensation of o-hydroxy aldehydes, secondary amines, and various boronic acids. It was observed that the reaction was completed in a short period of time and the yield was optimum by virtue of chitosan heterogeneous catalyst. Furthermore, the catalyst can be recovered by simple filtration and reused up to ten cycles. Smooth loss of catalytic activity was observed from the 6th cycle of reuse. Graphical abstract image
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Using N-substituted-2-amino-4,6-dimethoxypyrimidines in the synthesis of aliphatic guanidines ()
Publication date: 26 August 2015 Source:Tetrahedron Letters, Volume 56, Issue 35 Author(s): Julian W. Shaw, Laure Barbance, David H. Grayson, Isabel Rozas The use of 2-chloro-4,6-dimethoxypyrimdine as a tool for the syntheses of substituted guanidines is presented. This method, that we had previously shown to be very useful for aromatic amines, introduces an atom economical, cost effective and environmentally safe method for the installation of the guanidine functionality in aliphatic primary and secondary amines. Graphical abstract image
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Reactions of O,O-dialkyldithiophosphoric acids with N-tert-butyl-2-bromo-2-methylpropanimine and its salts ()
Publication date: 26 August 2015 Source:Tetrahedron Letters, Volume 56, Issue 35 Author(s): Mukattis B. Gazizov, Rafail A. Khairullin, Nikita G. Aksenov, Oleg G. Sinyashin The reactions of O,O-dialkyldithiophosphoric acids with N-tert-butyl-2-bromo-2-methylpropanimine and its salts resulted in reduction of the carbon–bromine bond in the iminium salt giving bis(dialkoxythiophosphoryl)disulfide and N-tert-butyl-2-methylpropaniminium bromide. This represents the first example of C–Br bond reduction by O,O-dialkyldithiophosphoric acids. Graphical abstract image
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Catalytic role of PPh3 and its polymer bound analog in the amidation of carboxylic acids mediated by 2,4,6-trichloro-1,3,5-triazine ()
Publication date: 26 August 2015 Source:Tetrahedron Letters, Volume 56, Issue 35 Author(s): Chuthamat Duangkamol, Subin Jaita, Sirilak Wangngae, Wong Phakhodee, Mookda Pattarawarapan The catalytic role of PPh3 and its polymer bound analog was investigated in the 2,4,6-trichloro-1,3,5-triazine (TCT) mediated amidation of carboxylic acids. In the presence of inorganic bases which were inert toward TCT, carboxylic acids rapidly reacted with amines to afford amides in good to excellent yields. The described method also enabled the synthesis of optically active protected dipeptides without racemization. Formation of triazinylphosphonium chloride during the PPh3 catalyzed acid activation was confirmed based on 31P NMR studies. Graphical abstract image
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CuO nanoparticles: synthesis and application as an efficient reusable catalyst for the preparation of xanthene substituted 1,2,3-triazoles via click chemistry ()
Publication date: 26 August 2015 Source:Tetrahedron Letters, Volume 56, Issue 35 Author(s): P. Iniyavan, G.L. Balaji, S. Sarveswari, V. Vijayakumar Copper(II) oxide (CuO) nanoparticles have been found to be an efficient catalyst for 1,3-dipolar cycloaddition (CuAAC) of aromatic azides and acetylenic xanthenes furnishing the corresponding xanthene substituted triazoles in excellent yields. CuO nanoparticles have been synthesized from copper acetate by simple co-precipitation method and characterized by scanning electron microscope, energy dispersive X-ray analysis, transmission electron microscope, and X-ray diffraction analysis. The salient features of the present protocol are mild reaction conditions, shorter reaction time, reusability of the catalyst, and applicability to a wide range of substrates. Graphical abstract image
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A new set of orthogonal protecting groups on a monosaccharide scaffold ()
Publication date: 26 August 2015 Source:Tetrahedron Letters, Volume 56, Issue 35 Author(s): Károly Ágoston, Gregory M. Watt, Péter Fügedi A monosaccharide unit was synthesized bearing four different temporary protecting groups. The protecting groups used (Fmoc carbonate, NAP ether, levulinoyl and chloroacetyl esters) and the anomeric thio-glycoside form a new set of orthogonal protecting groups. The orthogonality of these groups has been demonstrated on the monosaccharide scaffold. Graphical abstract image
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Penioxalicin, a novel 3-nor-2,3-seco-labdane type diterpene from the fungus Penicillium oxalicum TW01-1 ()
Publication date: 26 August 2015 Source:Tetrahedron Letters, Volume 56, Issue 35 Author(s): Xiqing Bian, Jiao Bai, Xiaolan Hu, Xin Wu, Chunmei Xue, Aihong Han, Guangyue Su, Huiming Hua, Yuehu Pei Penioxalicin (1), the first 3-nor-2,3-seco-labdane type diterpene featuring the fission between C-2 and C-3 in the ring A and the decarboxylation at C-3, was isolated from the fungus Penicillium oxalicum TW01-1. Its planar structure and absolute configuration were elucidated mainly by analysis of 1D and 2D-NMR, ECD spectroscopic data, and single-crystal X-ray diffraction. Compound 1 showed moderate cytotoxicity against HL-60 cell line. The possible biosynthetic pathway of 1 was also proposed. Graphical abstract image
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An improved and scalable synthesis of N-(5-(4-cyanophenyl)-3-hydroxypicolinoyl)glycine, a promising PHD2 inhibitor for the treatment of anemia ()
Publication date: 26 August 2015 Source:Tetrahedron Letters, Volume 56, Issue 35 Author(s): Yonghua Lei, Tianhan Hu, Mingyang Hu, Li Yang, Yue Wu, Hua Xiang, Lianshan Zhang, Lingjia Shen, Qidong You, Xiaojin Zhang An improved and scalable synthetic method of N-(5-(4-cyanophenyl)-3-hydroxypicolinoyl)glycine, a promising inhibitor of PHD2, is described. The optimized route staring from commercially available 5-bromo-3-nitropicolinonitrile takes only five chemical steps and has a dramatically increased total yield of 37.6% without chromatographic purifications. Graphical abstract image
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Isolation and structure elucidation of a novel resveratrol tetramer, vaticanol K, with a fused 2,7-dihydrooxepine–quinone methide from Vatica chinensis ()
Publication date: 26 August 2015 Source:Tetrahedron Letters, Volume 56, Issue 35 Author(s): Tetsuro Ito, Munekazu Iinuma A new resveratrol tetramer, vaticanol K (1) was isolated from the stem of Vatica chinensis. On the basis of combined spectroscopic analyses, the compound was structurally elucidated. Compound 1 possesses an unprecedented fused 2,7-dihydrooxepine–quinone methide skeleton presumably derived from the concerted intramolecular cyclization of two resveratrol dimers followed by desaturation extending conjugation. Graphical abstract image
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FRET-based rhodamine–coumarin conjugate as a Fe3+ selective ratiometric fluorescent sensor in aqueous media ()
Publication date: 26 August 2015 Source:Tetrahedron Letters, Volume 56, Issue 35 Author(s): Jing-can Qin, Zheng-yin Yang, Guan-qun Wang, Chao-rui Li In this study, a novel ratiometric fluorescent sensor (HL) for Fe3+ based on the conjugation of rhodamine and coumarin has been designed and synthesized. The free sensor displays fluorescence emission at 475nm, on the addition of Fe3+ to an aqueous solution of HL, the sensor shows significant fluorescence enhancement at 550nm which should be attributed to an intramolecular fluorescence resonance energy transfer (FRET) mechanism from coumarin to Rhodamine 6G. Graphical abstract image
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Development of a highly selective colorimetric pyrophosphate probe based on a metal complex and gold nanoparticles: change in selectivity induced by metal ion tuning of the metal complex ()
Publication date: 26 August 2015 Source:Tetrahedron Letters, Volume 56, Issue 35 Author(s): Sudeok Kim, Min Sik Eom, Soyeon Yoo, Min Su Han In this study, we developed a colorimetric sensing system for pyrophosphate (PPi) with a probe composed of phosphate functionalized-gold nanoparticles as the reporter unit and [Cu3(1,3,5-tris[bis(pyridine-2-ylmethyl)aminomethyl]-2,4,6-triethylbenzene)]6+ (2) as the receptor unit. The proposed probe allows easy detection of PPi with the naked eye, and selectively recognizes PPi with a detection limit of 320nM. Unlike previous AuNP based-PPi sensing systems, this probe exhibits high selectivity for PPi over various other phosphate derivatives including adenosine triphosphate (ATP) and adenosine diphosphate (ADP). Graphical abstract image
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1,8-Naphthyridine-based boron complexes: visible colorimetric probes for highly selective sensing of phosphoric ion ()
Publication date: 26 August 2015 Source:Tetrahedron Letters, Volume 56, Issue 35 Author(s): Gao Fen Wu, Qiu Lin Xu, Lin E. Guo, Tie Nan Zang, Rui Tan, Si Ting Tao, Jian Fei Ji, Rui Ting Hao, Jun Feng Zhang, Ying Zhou Two 1,8-naphthyridine-based N,O-chelated boron complexes (1 and 2) were designed as novel phosphate ion (Pi) probes, which are based on a methoxy oxalyl group reaction site. These two probes showed high selectivity for Pi detection without interference from ATP, PPi, or other anions. Dramatic color changes from colorless to light yellow were observed by addition of Pi to solutions of 1 and 2 in DMSO/HEPES buffer (0.02M, pH 7.4) (V/V=8:2). This qualitative color shift was accompanied by red-shifts in the UV–vis absorbance spectrum of approximately 43nm for 1 and 46nm for 2. Fluorescence quenching was observed in solutions of 1 (Φ =0.31) and 2 (Φ =0.23) upon addition of Pi. Probes 1 and 2 are the first two 1,8-naphthyridine-based boron complexes developed which serve as colorimetric probes capable of highly selective detection of Pi over other phosphate-based chemical species including P2O7 4−, ATP, ADP, AMP, GTP, GDP, GMP, TTP, TDP, TMP, UTP, UDP, and UMP. The in vivo imaging results demonstrate that 1 and 2 are able to permeate into the HeLa cells and Caenorhabditis elegans to detect Pi via a strong fluorescence intensity change. Graphical abstract image
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A novel Friedel–Crafts alkylation of naphthols without Lewis acid ()
Publication date: 26 August 2015 Source:Tetrahedron Letters, Volume 56, Issue 35 Author(s): Yijun Zhu, Kuaile Lin, Deyong Ye, Weicheng Zhou A novel Friedel–Crafts alkylation of α- or β-naphthols with a variety of β-haloketones is described. The reaction was environmentally-friendly performed under mild conditions without any Lewis acid and in good to excellent yields. Graphical abstract image
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Can hydrogen-bonding donors abstract chloride from LAu(I)Cl complexes: a computational study ()
Publication date: 26 August 2015 Source:Tetrahedron Letters, Volume 56, Issue 35 Author(s): Benjamin W. Gung, Steven C. Schlitzer Computational study has shown that it is possible to abstract the chloride anion from LAu(I)Cl complexes by well-designed effective chloride receptors. A new receptor with two squaramides and an anthracene spacer was found to be a stronger chloride abstractor than the corresponding receptor with a decalin scaffold. Graphical abstract image
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Dithiocarbamate-substituted gem-difluorinated silicon reagent: generation and addition to aldehydes ()
Publication date: 26 August 2015 Source:Tetrahedron Letters, Volume 56, Issue 35 Author(s): Anton S. Maslov, Vladimir O. Smirnov, Marina I. Struchkova, Dmitry E. Arkhipov, Alexander D. Dilman A new gem-difluorinated silicon reagent bearing a pyrrolidine dithiocarbamate substituent was prepared by the reaction of (bromodifluoromethyl)trimethylsilane with the corresponding potassium dithiocarbamate. The obtained reagent was employed in the nucleophilic addition to aldehydes and ketones. Graphical abstract image
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Synthesis and use of new C-glycosyl bicyclic lactones ()
Publication date: 26 August 2015 Source:Tetrahedron Letters, Volume 56, Issue 35 Author(s): Arkadiusz Listkowski, Otman Otman, Stéphane Chambert, Yves Queneau New C-glycosyl bicyclic lactones have been synthesized in three steps from glycosyl bromides and used as synthons towards C-glycosyl derivatives which can readily be elaborated to 1,2-bisfunctionalized carbohydrate systems. The method was illustrated with several examples of pseudo conjugates prepared from the new C-glycosyl 1,2-fused pyrano-δ-lactonic building blocks, either with groups such as allyl or propargyl with wide subsequent reactivity, or with more elaborated moieties leading to model glycoaminoacids or pseudo nucleotide sugars. Graphical abstract image
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Straightforward and one-pot synthesis of bifunctional phosphorus Betti bases under solvent-free conditions via phosphine oxide component ()
Publication date: 26 August 2015 Source:Tetrahedron Letters, Volume 56, Issue 35 Author(s): Fengjiao Liu, Guozhu Li, Jie Jiang, Fangying Zheng, Mingshu Wu Straightforward and one-pot strategy to synthesize the bifunctional phosphorus Betti bases under solvent-free conditions via the condensation of 2-naphthol, aryl aldehydes and the diphenylphosphine oxide has been developed in the presence of p-toluenesulfonic acid for the first time. The entitled compounds are obtained in good yields and fully characterized by NMR, MS, IR and elemental analysis. Graphical abstract image
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Editorial board ()
Publication date: 19 August 2015 Source:Tetrahedron Letters, Volume 56, Issue 34
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Graphical Contents List ()
Publication date: 19 August 2015 Source:Tetrahedron Letters, Volume 56, Issue 34
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An example of a stepwise mechanism for the catalyst-free 1,3-dipolar cycloaddition between a nitrile oxide and an electron rich alkene ()
Publication date: 19 August 2015 Source:Tetrahedron Letters, Volume 56, Issue 34 Author(s): Seyyed Amir Siadati The present Letter studies possible pathways for the non-catalyzed 1,3-dipolar cycloaddition (1,3-DC) reaction between a nitrile oxide derivative and a highly electron-rich alkene. A diagram of the free energy surface during the reaction coordinate was prepared by considering all routes of the 1,3-DC reaction between methyl nitrile oxide and tetraamino ethylene and by detecting any possible species which could form in the course of the predicted pathways. The results indicated that the stepwise pathway was preferable in comparison with the concerted route. Therefore, it was concluded that a switching of the mechanism from concerted to stepwise was the outcome when using strong electron donor functional groups on the dipolarophile. Graphical abstract image
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Synthesis of primary amides by aminocarbonylation of aryl/hetero halides using non-gaseous NH3 and CO sources ()
Publication date: 19 August 2015 Source:Tetrahedron Letters, Volume 56, Issue 34 Author(s): A.S. Suresh, Poongavanam Baburajan, Mansur Ahmed A practically simple method for the synthesis of primary amides via the palladium-catalysed aminocarbonylation of aromatic halides by using solid sources of gaseous ammonia and carbon monoxide is described. The system tolerated a wide variety of hindered and functionalized aryl/hetero halides and afforded good to excellent yields (69–94%) of the amide. Pharmacologically active Exalamide and Pyrazinecarboxamide were synthesised in high yields to demonstrate the effectiveness of this method. Graphical abstract image
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Synthesis of a pyrene-fused aza-BODIPY as a near-infrared dye having the absorption maximum at 746nm ()
Publication date: 19 August 2015 Source:Tetrahedron Letters, Volume 56, Issue 34 Author(s): Xin-Dong Jiang, Dongmei Xi, Chang-liang Sun, Jian Guan, Mingrui He, Lin-Jiu Xiao A novel pyrene-fused pyrrole was developed by the reaction of 9,10-dihydrobenzo[pqr]tetraphen-7(8H)-one with 3-phenyl-2H-azirine in the presence of NaH. Utilizing this pyrrole, the symmetric pyrene-containing aza-BODIPY has been prepared in the NIR region (λ abs =746nm, λ em =762nm) as a result of the combined effect of the rigidization and the extension of the π-conjugation. The decrease in the HOMO–LUMO band gap for the lowest energy absorption bands was observed in the pyrene-fused aza-BODIPY. Graphical abstract image
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Synthesis of gold nanoparticles using electron-donating dithiafulvene units ()
Publication date: 19 August 2015 Source:Tetrahedron Letters, Volume 56, Issue 34 Author(s): Anabel E. Lanterna, Eduardo A. Coronado, Alejandro M. Granados Dithiafulvene (DTF) derivative compounds were used as reducing agents to synthesize capped gold nanoparticles (AuNPs). DTF derivatives had shown good capability to reduce Au(III) to Au(0) without further addition of common reducing agents, and at the same time they were able to act as good capping agents. Because of their spectroscopic characteristics we were able to follow the AuNP formation by UV–Vis spectroscopy. Raman and NMR experiments were also performed in order to estimate the composition of the final capped AuNP species. Graphical abstract image
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A practical process for the preparation of bis(2,2,2-trifluoroethyl) 2-oxoalkylphosphonates by acylation with carboxylic esters ()
Publication date: 19 August 2015 Source:Tetrahedron Letters, Volume 56, Issue 34 Author(s): Katalin Molnár, László Takács, Mihály Kádár, Ferenc Faigl, Zsuzsanna Kardos The preparation of bis(2,2,2-trifluoroethyl) 2-oxoalkylphosphonates by the acylation of bis(2,2,2-trifluoroethyl) methylphosphonate was re-investigated using esters rather than the sensitive acyl chlorides. Based on our optimization, the best results were achieved when the base (LiHMDS) was added to a solution of the phosphonate and the acylating agent at −90°C. Graphical abstract image
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Synthesis of tetrafunctionalized pentiptycenequinones for construction of cyclic dimers with a cylindrical shape by boronate ester formation ()
Publication date: 19 August 2015 Source:Tetrahedron Letters, Volume 56, Issue 34 Author(s): Shigehisa Akine, Daisuke Kusama, Yuri Takatsuki, Tatsuya Nabeshima New tetrasubstituted pentiptycenequinone derivatives 1 and 2 having two sets of diol moieties in a syn orientation were synthesized from the corresponding 2,3-disubstituted anthracene derivatives. The semicircular scaffold of these molecules is expected to be useful to create a belt-like structure having an aromatic π-wall. Indeed, the reaction of 1 with 1,4-phenylenediboronic acid or 4,4′-biphenyldiboronic acid quantitatively gave a 2:2 macrocyclic product via boronate ester formation. The efficient formation of these cyclic structures can be explained by favorable intramolecular cyclization at the final step. Graphical abstract image
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Acceptorless dehydrogenative synthesis of benzothiazoles and benzimidazoles from alcohols or aldehydes by heterogeneous Pt catalysts under neutral conditions ()
Publication date: 19 August 2015 Source:Tetrahedron Letters, Volume 56, Issue 34 Author(s): Chandan Chaudhari, S.M.A. Hakim Siddiki, Ken-ichi Shimizu Pt/Al2O3 and Pt/TiO2 were effective catalysts for the synthesis of 2-substituted benzothiazoles and benzimidazoles from 2-aminothiophenol and 1,2-phenylenediamine with alcohols or aldehydes under acceptor-free and additive-free conditions. Graphical abstract image
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Atropisomerism in azadipeptides: evaluation of N1-methylation and thioamide introduction ()
Publication date: 19 August 2015 Source:Tetrahedron Letters, Volume 56, Issue 34 Author(s): Philipp A. Ottersbach, Gregor Schnakenburg, Michael Gütschow Cbz-protected azadipeptides, designed as structurally reduced model compounds, were synthesized and investigated with respect to the occurrence of atropisomerism. Methylation at the carbamate nitrogen caused mixtures of E and Z isomers in Cbz-sarcosyl-azaglycine-amide (9) and Cbz-sarcosyl-methylazaalanine-amide (10). A formal O/S exchange led to Cbz-glycyl-azaglycine-thioamide (11) and Cbz-glycyl-methylazaalanine-thioamide (12), respectively. The (MeN)2 fragment, present in 10 and 12 (but not 9 and 11), serves as a chirality-inducing element owing to a restricted rotation around the N–N axis. Graphical abstract image
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A convenient entry to indolizidine alkaloids using Kharasch type reactions ()
Publication date: 19 August 2015 Source:Tetrahedron Letters, Volume 56, Issue 34 Author(s): Maricela Morales-Chamorro, Jorge Meza-González, Alejandro Cordero-Vargas A convenient entry to indolizidine alkaloids based on a free-radical atom transfer reaction (ATRA or Kharasch reaction) as the key step is reported. The strategy is based on the free radical reaction between ethyl iodoacetate and an l-proline derivative serving as a radical acceptor. The key intermediate obtained after the radical reaction is used for the synthesis of indolizidine (−)-167B and of an advanced intermediate for the synthesis of (+)-dendroprimine. Graphical abstract image
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Preparation of 2,3-unsaturated pseudoglycosides with Ferrier Rearrangement promoted by Tm(OTf)3 as a highly efficient catalyst ()
Publication date: 19 August 2015 Source:Tetrahedron Letters, Volume 56, Issue 34 Author(s): Peiran Chen, Bin Bi By using Tm(OTf)3 as the catalyst, an efficient Ferrier Rearrangement reaction system has been established. A series of O-, S-, N-, and C-2, 3-unsaturated-glucosides were obtained in good yields and high anomeric selectivities by the glycosidation of 3,4,6-tri-O-acetyl-d-glucal or 3,4-di-O-acetyl-l-rhamnal with the corresponding nucleophiles, including azaglycosylation with N-nucleophiles. Graphical abstract image
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Computationally driven reassignment of the structures of aldingenins A and B ()
Publication date: 19 August 2015 Source:Tetrahedron Letters, Volume 56, Issue 34 Author(s): Olga A. Mukhina, Hiroyuki Koshino, Michael T. Crimmins, Andrei G. Kutateladze Earlier four brominated sesquiterpenes, aldingenins A–D, were isolated from the red algae Laurencia aldingensis, and their structure elucidated by spectroscopic methods including NMR. Total syntheses of the proposed structures of aldingenin B (Org. Lett. 2012, 14, 2168) and aldingenin C (J. Org. Chem. 2014, 79, 9373) have demonstrated that the structures are misassigned. Koshino has proposed aldingenins C and D to be caespitol and 5-(S)-acetoxycaespitol. Computational evidence presented in this Letter and based primarily on the computed proton spin–spin coupling constants (but also including 13C NMR chemical shifts) leads to the conclusion that the remaining two aldingenins A and B are also halogenated sesquiterpenes of the same caespitol family. Aldingenin A is assigned the structure of 5-(S)-hydroxycaespitol 1, and aldingenin B—hemiacetal 2 of a related 8-oxo compound. Graphical abstract image
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A safe and scalable synthesis of 2-hydroxy-3-alkoxypropionates by epoxide ring opening ()
Publication date: 19 August 2015 Source:Tetrahedron Letters, Volume 56, Issue 34 Author(s): Michael J. Waring, Stuart N.L. Bennett, Leonie Campbell, Stephen Hallam, Nathaniel G. Martin, Christopher Tickner Epoxides are useful precursors for the synthesis of hydroxyl-bearing building blocks via Lewis acid catalyzed, nucleophilic ring opening. However, the reaction of glycidate esters with alcohol nucleophiles can be quite challenging with many of the classical paradigms for epoxide opening failing to give efficient reaction. In our hands, the most efficient catalyst described in the literature for effecting this transformation was magnesium perchlorate. However, ring opening of methyl glycidate with this catalyst revealed the potential for rapid and uncontrollable decomposition with onset at a relatively low temperature. Herein, the development of an alternative process, which is safe and scalable, is described. This allowed the synthesis of a series of novel 2-hydroxy-3-alkoxypropionates. Graphical abstract image
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Binding studies of diorganochalcogenides with Hg(II) in solution ()
Publication date: 19 August 2015 Source:Tetrahedron Letters, Volume 56, Issue 34 Author(s): Prakul Rakesh, Harkesh B. Singh, Jerry P. Jasinski, James A. Golen A series of organochalcogen tridentate ligands containing N, Se/Te, N donor atoms has been synthesized. Three fluorophore ligands show that Hg2+ ions can be selectively detected in the presence of different interfering cations, that is, Zn2+, Cd2+, Cu2+, Co2+, Ni2+, Ca2+, Na+, K+ and Ag+. Graphical abstract image
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What is the absolute configuration of (+)-crispatanolide isolated from Makinoa crispata (liverwort)? ()
Publication date: 19 August 2015 Source:Tetrahedron Letters, Volume 56, Issue 34 Author(s): Katsuyuki Nakashima, Hiroyuki Kawano, Minako Kumano, Hikari Kodama, Masayo Kameoka, Akiyo Yamamoto, Reiko Mizutani, Masakazu Sono, Motoo Tori Crispatanolide, which was isolated from Makinoa crispata (liverwort) in 1980, was synthesized in its chiral form starting from 3-substituted-2-bromocyclohex-2-en-1-one using CBS reduction. The absolute configuration was established using the modified Mosher method on the CBS reduction product. This synthesis established the absolute configuration of the natural product, which is presumably derived from a 10β-methyl-7-βH-eudesmane type precursor. Graphical abstract image
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Chemoenzymatic total synthesis of four stereoisomers of centrolobine ()
Publication date: 19 August 2015 Source:Tetrahedron Letters, Volume 56, Issue 34 Author(s): Bollipalli Nagarjuna, Barla Thirupathi, Chunduri Venkata Rao, Debendra K. Mohapatra Four stereoisomers of centrolobine, (3R,7S)-(−)-centrolobine (1), (3S,7S)-(−)-epi-centrolobine (2), (3S,7R)-(+)-centrolobine (3), and (3R,7R)-(+)-epi-centrolobine (4) have been achieved in an efficient manner in 24–28% overall yield over 9–10 linear steps starting from cheap and commercially available 4-methoxybenzaldehyde following chemoenzymatic protocol. The key features of this synthetic protocol are enzymatic resolution, cross-metathesis (CM), and our own developed tandem isomerization followed by C–O and C–C bond formation reaction. Graphical abstract image
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Hg2+-selective dual signaling probe based on a thio-functionalized rhodamine B hydroxamic acid ()
Publication date: 19 August 2015 Source:Tetrahedron Letters, Volume 56, Issue 34 Author(s): Yong Ae Jeong, Jiyoung Choi, Suk-Kyu Chang A new Hg2+-selective signaling system based on a thio-functionalized rhodamine B hydroxamic acid was investigated. A thio-analogue of rhodamine B hydroxamic acid had a distinct Hg2+-selective signaling behavior in aqueous solution, whereas its parent hydroxamic acid was completely unreactive toward any metal ions. Selective chromogenic and fluorogenic signaling of Hg2+ by the thio-functionalized rhodamine B hydroxamic acid in aqueous solution was possible with a detection limit of 1.0×10−6 M. Hg2+ determination based on paper test strips was conducted as a practical application. Graphical abstract image
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An efficient iron-catalyzed S-arylation of aryl and alkylthiols with aryl halides in the presence of water under aerobic conditions ()
Publication date: 19 August 2015 Source:Tetrahedron Letters, Volume 56, Issue 34 Author(s): K.S. Sindhu, Amrutha P. Thankachan, Anns Maria Thomas, Gopinathan Anilkumar In this study, an environmentally benign FeCl3·6H2O/l-proline catalytic system in the presence of TBAB was employed as a catalyst for the coupling reactions of aryl halides with aryl and alkyl thiols in water under aerobic conditions. The versatility, low cost, and environmental friendliness, in combination with high yields, makes the procedure noteworthy. This protocol offers a simple and efficient thioetherification method for aryl halides. Graphical abstract image
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Nitronium salts as novel reagents for the heterocyclization of gem-bromofluorocyclopropanes into pyrimidine derivatives ()
Publication date: 19 August 2015 Source:Tetrahedron Letters, Volume 56, Issue 34 Author(s): Kseniya N. Sedenkova, Elena B. Averina, Yuri K. Grishin, Aleksandr B. Bacunov, Sergey I. Troyanov, Igor V. Morozov, Evgeniya B. Deeva, Anna V. Merkulova, Tamara S. Kuznetsova, Nikolay S. Zefirov A number of nitrosonium and nitronium salts were probed as reagents for the heterocyclization of 1-bromo-1-fluorocyclopropanes in the presence of organic nitriles to give pyrimidine N-oxides. Nitronium triflate, either preformed or generated in situ from nitric and triflic acids, was shown to be the most efficient reagent for this reaction, affording a mild and convenient procedure for the synthesis of 4-halogenopyrimidine derivatives. X-ray crystallography was used to confirm the ionic structure of nitronium triflate (NO2 +)(CF3SO3 −). Graphical abstract image
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Total synthesis of heliespirone B ()
Publication date: 19 August 2015 Source:Tetrahedron Letters, Volume 56, Issue 34 Author(s): Li Yang, Jing Feng, Jinpeng Li, Bo Liu The highly diastereoselective total synthesis of heliespirone B, an oxaspirocyclic compound isolated from the leaves of Helianthus annuus, has been accomplished from (R)-curcuphenol. Key transformations include the formation of an oxaspirocyclic structure via a highly diastereoselective oxa-Michael reaction. Graphical abstract image
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Noncovalent catalysis of glucose-containing imidazolium salt in solvent-free one-pot synthesis of Ortho-aminocarbonitriles ()
Publication date: 19 August 2015 Source:Tetrahedron Letters, Volume 56, Issue 34 Author(s): Li-zhuo Zhang, Yu Wan, Xiao-xiao Zhang, Hao Cui, Huan Zou, Qiu-ju Zhou, Hui Wu A glucose-containing imidazolium salt β-1-imidazole-2,3,4,6-tetraacetyl-D-glucopyranosyl bromide was firstly used as efficient noncovalent organocatalyst to promote the solvent-free preparation of ortho-aminocarbonitriles via a four-component condensation of aromatic aldehyde, cyclohexanone, and 2equiv of malononitrile at room temperature. Seven bonds were cleaved while four new bonds were formed and a six-membered ring was constructed in one-pot. Graphical abstract image
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Cationic rhodium(I)/BIPHEP complex-catalyzed cross-cyclotrimerization of silylacetylenes and unsymmetrical electron-deficient internal alkynes ()
Publication date: 19 August 2015 Source:Tetrahedron Letters, Volume 56, Issue 34 Author(s): Arisa Heya, Tomoya Namba, Jun Hara, Yu Shibata, Ken Tanaka It has been established that a cationic rhodium(I)/BIPHEP complex catalyzes the chemo- and regioselective intermolecular cross-cyclotrimerization of silylacetylenes with unsymmetrical electron-deficient internal alkynes. Chemoselectivity was highly dependent on steric bulk of the unsymmetrical electron-deficient internal alkynes used. Two molecules of sterically less demanding alkynoates and alkynone reacted with one molecule of the silylacetylene, on the contrary, one molecule of a sterically demanding alkynoate reacted with two molecules of the silylacetylene. Graphical abstract image
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Iron-catalyzed oxidative dehydrogenative coupling of ethers with aryl tetrazoles ()
Publication date: 19 August 2015 Source:Tetrahedron Letters, Volume 56, Issue 34 Author(s): Kai-qiang Zhu, Liang Wang, Qun Chen, Ming-yang He An iron-catalyzed oxidative dehydrogenative coupling of ethers with aryl tetrazoles has been developed. A wide variety of tetrazoles and ethers survived the reaction conditions to deliver the corresponding hemiaminal derivatives in moderate to good yields. Graphical abstract image
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Total synthesis and stereochemical reassignment of maedamide ()
Publication date: 19 August 2015 Source:Tetrahedron Letters, Volume 56, Issue 34 Author(s): Ayano Takayanagi, Arihiro Iwasaki, Kiyotake Suenaga The first total synthesis of maedamide, an acyclic peptide isolated from a marine cyanobacterial assemblage of Lyngbya sp., was achieved. This synthesis led to reassignment of the allo-d-Ile of maedamide to be l-Ile, which was supported by 1H and 13C NMR data. Graphical abstract image
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Direct C–H arylation of benzothiazoles by magnetically separable nano copper ferrite, a recyclable catalyst ()
Publication date: 19 August 2015 Source:Tetrahedron Letters, Volume 56, Issue 34 Author(s): G. Satish, K. Harsha Vardhan Reddy, B.S.P. Anil, K. Ramesh, R. Uday Kumar, Y.V.D. Nageswar A simple and highly practical method for the direct C–H arylation of benzothiazoles has been developed by using nano copper ferrite as a recyclable catalyst. The CuFe2O4 nano could be recovered and reused without significant loss of catalytic activity. Graphical abstract image
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A facile synthesis of 2-(2-phenyl-4H-chromen-4-ylidene)-2H-indene-1,3-diones and related compounds involving an interesting aerial oxidation ()
Publication date: 19 August 2015 Source:Tetrahedron Letters, Volume 56, Issue 34 Author(s): Chayan Guha, Swati Samanta, Nayim Sepay, Asok K. Mallik 2-(2-Phenyl-4H-chromen-4-ylidene)-2H-indene-1,3-diones were obtained in good to excellent yields by treatment of 2-hydroxychalcones and indane-1,3-dione in refluxing toluene in the presence of amberlyst-15 as catalyst in air. The reaction involving 2-hydroxychalcones and cyclopentane-1,3-dione under the same condition gave 2-(2-phenyl-4H-chromen-4-ylidene)cyclopentane-1,3-diones along with 2,8-dioxabicyclo[3.3.1]nonanes, the relative amount of the products being dependent on the reaction time. Separate experiments have shown that the isolated 2,8-dioxabicyclo[3.3.1]nonanes are convertible to the other type of products under the applied reaction condition. Graphical abstract image
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