Tetrahedron Letters

Editorial board ()
Publication date: 11 February 2015 Source:Tetrahedron Letters, Volume 56, Issue 7
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Graphical Contents List ()
Publication date: 11 February 2015 Source:Tetrahedron Letters, Volume 56, Issue 7
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Carbon–fluorine bond activation for the synthesis of functionalized molecules ()
Publication date: 11 February 2015 Source:Tetrahedron Letters, Volume 56, Issue 7 Author(s): Teresa A. Unzner , Thomas Magauer The synthesis of fluorinated compounds as well as the use of these products as building blocks for the preparation of complex molecules are fast growing research areas. Herein we highlight recent progress in the activation of allylic and benzylic C–F bonds for the synthesis of functionalized molecules. SN2′ reactions of allylic difluoro and trifluoro compounds as well as transition-metal-catalyzed (nickel, palladium, platinum and copper) processes are described. The C–F bond activation of 3-fluoropropenes was achieved with platinum- or organocatalysis. Benzylic C–F bond activation was realized with magnesium by deprotonation leading to the formation of reactive quinone methide intermediates and with hydrogen bond donors by forming strong F⋯H interactions. Graphical abstract image
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Biomolecule-compatible chemical bond-formation and bond-cleavage reactions induced by visible light ()
Publication date: 11 February 2015 Source:Tetrahedron Letters, Volume 56, Issue 7 Author(s): Chenchen Hu , Yiyun Chen Biomolecule-compatible reactions are useful for biomolecule labeling and manipulations. Light-induced chemical reactions provide high spatial and temporal precision, and visible light imposes less damage to biomolecules compared to UV light. The visible-light-induced biomolecule-compatible reactions reported in the literatures are categorized by reaction mechanisms to oxidative-quench, reductive-quench, and energy-transfer pathways. Their inventions and applications are discussed with the focus on biomolecule-compatibility. Graphical abstract image
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An efficient one-pot oxidative esterification of aldehydes to carboxylic esters using B(C6F5)3–TBHP ()
Publication date: 11 February 2015 Source:Tetrahedron Letters, Volume 56, Issue 7 Author(s): Sravanthi Devi Guggilapu , Santosh Kumar Prajapti , Bathini Nagendra Babu A simple and efficient protocol for oxidative esterification of diverse aldehydes with alcohols was accomplished with tert-butyl hydroperoxide and 1mol% of tris(pentafluorophenyl)borane [B(C6F5)3] to generate the corresponding esters in good to excellent yields. The present protocol represents compatibility with wide range of functional groups as well as exceptional tolerance toward acid labile protecting groups such as TBDPS, TBDMS, acetonide, and Boc. Graphical abstract image
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Divergent and facile Lewis acid-mediated synthesis of N-alkyl 2-aminomethylene-1,3-indanediones and 2-alkylamino-1,4-naphthoquinones ()
Publication date: 11 February 2015 Source:Tetrahedron Letters, Volume 56, Issue 7 Author(s): Qian Zhang , Cheng-Wei Tom Chang N-Alkyl 2-aminomethylene-1,3-indanediones and 2-alkylamino-1,4-naphthoquinones are known for their diverse and versatile bioactivities and applications. Traditionally, these two compounds were synthesized in separate routes using different materials. By employing Lewis acid, cycloaddition of alkyl azides and 1,4-naphthoquinone can provide these two classes of compound in one-pot fashion. Among the Lewis acids and conditions examined, TMSOTf under reflux offers the best overall yields. In addition, the purification of both classes of compounds can be easily achieved using flash column chromatography making this methodology feasible for scale-up synthesis of compounds with biological interests. Graphical abstract image
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Reevaluation of the 2-nitrobenzyl protecting group for nitrogen containing compounds: an application of flow photochemistry ()
Publication date: 11 February 2015 Source:Tetrahedron Letters, Volume 56, Issue 7 Author(s): Chloe I. Wendell , Michael J. Boyd Photochemistry under continuous flow conditions has many potential benefits for photochemical reactions that are problematic in batch. The 2-nitrobenzyl moiety is a photolabile protecting group for nitrogen. However, N-deprotection is generally impractical and, therefore, has not been extensively adopted. This Letter reports significant improvements in the N-deprotection of the 2-nitrobenzyl group through the application of continuous flow photolysis. This procedure was applied to a variety of substrates including indoles, indazoles, pyrazoles and secondary amines. Significant improvement in yield, reaction time and scalability was observed under continuous flow conditions. Graphical abstract image
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Synthesis of a pentasaccharide repeating unit of the O-specific polysaccharide from the lipopolysaccharide of Providencia alcalifaciens O28 ()
Publication date: 11 February 2015 Source:Tetrahedron Letters, Volume 56, Issue 7 Author(s): Pintu Kumar Mandal , Pratik Rajesh Chheda A straightforward convergent synthetic strategy has been developed for the synthesis of the pentasaccharide repeating unit of the O-specific cell wall lipopolysaccharide of Providencia alcalifaciens O28. The target pentasaccharide has been synthesized in excellent yield using a [3+2] block glycosylation approach with minimum number of steps. Here H2SO4–silica has been used successfully as a promoter for glycosylation reaction. All glycosylation steps are high yielding and stereoselective. Graphical abstract image
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Metal-free multicomponent coupling reaction of aliphatic amines, formaldehyde, organoboronic acids, and propiolic acids for the synthesis of diverse propargylamines ()
Publication date: 11 February 2015 Source:Tetrahedron Letters, Volume 56, Issue 7 Author(s): Jiayi Wang , Qiaoying Shen , Jiayu Zhang , Gonghua Song A metal-free multicomponent coupling reaction of aliphatic amines, formaldehyde, organoboronic acids, and propiolic acids has been reported for the synthesis of diverse propargylamines. This transformation involves a MCR2 of PBM and decarboxylative three-component coupling reactions. Graphical abstract image
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Facile synthesis of functionalized 1H-pyrrolo[2,3-b]quinolines via Ugi four-component reaction followed by Cu-catalyzed aryl-amide, C–N bond coupling ()
Publication date: 11 February 2015 Source:Tetrahedron Letters, Volume 56, Issue 7 Author(s): Mrityunjaya Asthana , Ritush Kumar , Tanu Gupta , Radhey M. Singh A simple one-pot two-step reaction comprising an Ugi four-component reaction (Ugi-4CR) and copper-catalyzed intramolecular amide-aryl cyclization of heteroaryl chloride with amide has been developed for the synthesis of functionalized 1H-pyrrolo[2,3-b]quinolines in moderate to good yields. The synthesized pyrrolo-fused quinoline was further examined for Pd-catalyzed intramolecular cyclization to afford [1,4]oxazine-fused pyrrolo quinoline 11 and to nucleophilic substitution reactions with allyl bromide and methyl iodide to afford the corresponding allyl and methyl ethers, 12 and 13, respectively. Graphical abstract image
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Organocatalyzed asymmetric synthesis and absolute configuration assignment of enantioenriched α-benzylaminocoumarins ()
Publication date: 11 February 2015 Source:Tetrahedron Letters, Volume 56, Issue 7 Author(s): Hua Lin , Yu Tan , Jian-Ming Wu , Xiao-Di Yang , Jun-Hua Chen , Xing-Wen Sun A cinchona alkaloid catalyzed asymmetric Mannich reaction of 4-hydroxycoumarins and N-p-tolylsulfinylimines was achieved to synthesize enantioenriched α-benzylaminocoumarins in moderate to excellent yields (up to 99%) and with moderate to good enantioselectivities (up to 83% ee). The absolute configuration of the resulting chiral amines was assigned by analysis of computational and experimental electronic circular dichroism (ECD) spectroscopies. Graphical abstract image
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Reduction of phosphine oxides to the corresponding phosphine derivatives in Mg/Me3SiCl/DMI system ()
Publication date: 11 February 2015 Source:Tetrahedron Letters, Volume 56, Issue 7 Author(s): Manabu Kuroboshi , Toshihito Kita , Asuka Aono , Toshimasa Katagiri , Seiya Kikuchi , Syoko Yamane , Hiromu Kawakubo , Hideo Tanaka Direct reductions of phosphine oxides to the corresponding phosphines were performed successfully by using Mg/Me3SiCl/DMI system. The reduction proceeded under mild conditions and was applicable to a wide range of phosphine oxides; triarylphosphine oxides, alkyldiarylphosphine oxides, and dialkylarylphosphine oxides gave the corresponding phosphines in good to excellent yields. Graphical abstract image
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Directed synthesis of 2-spiroindolines from indole derivatives by formic acid-induced N-acyliminium ion-conjugated diene spirocyclization ()
Publication date: 11 February 2015 Source:Tetrahedron Letters, Volume 56, Issue 7 Author(s): Hideki Abe , Naohiro Miyagawa , Sho Hasegawa , Toyoharu Kobayashi , Sakae Aoyagi , Chihiro Kibayashi , Tadashi Katoh , Hisanaka Ito Synthesis of 2-spiroindolines from 2-substituted indole derivatives via acid-induced N-acyliminium ion-conjugated diene spirocyclization was demonstrated. This methodology can be used to direct transformations of 2-substituted indole moieties into 3-nonsubstituted-2-spiroindoline skeletons. Graphical abstract image
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Synthesis of (Z)-fluoroallyl azides through aluminium-mediated defluorinative functionalization reactions ()
Publication date: 11 February 2015 Source:Tetrahedron Letters, Volume 56, Issue 7 Author(s): Azusa Sato , Hikaru Yanai , Daiki Suzuki , Midori Okada , Takeo Taguchi The reaction of difluorohomoallyl alcohols with Me2AlCl in CH2Cl2 selectively gave (Z)-fluoroallyl chlorides via SN2′ type defluorinative chlorination. These chlorides were easily converted to the corresponding (Z)-fluoroallyl azides by the sequential nucleophilic azidation reaction using NaN3. Direct defluorinative azidation of the difluorohomoallyl alcohols was also achieved by treating with Me3SiN3 in the presence of Al(Oi-Pr)3. Fluoroallyl azides thus obtained successfully applied to the Huisgen 1,3-dipolar cycloaddition chemistry. Graphical abstract image
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A general route to the synthesis of indoloazocines using allyl bromides prepared from Morita–Baylis–Hillman adducts ()
Publication date: 11 February 2015 Source:Tetrahedron Letters, Volume 56, Issue 7 Author(s): Garima Pandey , Ruchir Kant , Sanjay Batra A general approach to the synthesis of (E)-5-(substituted) benzylidene-2,3,4,5-tetrahydro-1H-azocino[5,4-b]indol-6(7H)-ones via intramolecular Friedel Craft’s reaction of allylamines prepared from tryptamine and allyl bromides is reported. Graphical abstract image
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Tetrabutylammonium dichlorobromide: an efficient and mild reagent for geminal bromochlorination of α-diazo carbonyl compounds ()
Publication date: 11 February 2015 Source:Tetrahedron Letters, Volume 56, Issue 7 Author(s): Nusrathulla Shariff , Selvam Mathi , Chidambaram Rameshkumar , Lourdusamy Emmanuvel An efficient and mild one-pot procedure for geminal bromochlorination of α-diazo carbonyl compounds has been developed for the first time using tetrabutylammonium dichlorobromide (TBADCB) via metal carbenoids. This protocol was found to be highly selective and does not result in dichlorination or dibromination products. The reagent, TBADCB, is commercially available, easy to prepare and handle. Graphical abstract image
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Synthesis of functionalized 1,2-dihydropyridines bearing quaternary carbon centers via an organocatalytic allylic alkylation ()
Publication date: 11 February 2015 Source:Tetrahedron Letters, Volume 56, Issue 7 Author(s): Gong-Feng Zou , Zhi-Peng Hu , Shi-Qiang Zhang , Wei-Wei Liao The first tertiary amine-catalyzed allylic alkylation of Reissert products of pyridine derivatives has been demonstrated. This protocol provided an efficient synthetic route for the construction of functionalized 2,2-disubstituted 1,2-dihydropyridines incorporating quaternary carbon centers with good to high regioselectivities and moderate enantioselectivities. Graphical abstract image
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Palladium catalyzed Suzuki Miyaura cross coupling of 3-chloroisochromen-1-one: synthesis of glomellin and reticulol analogues ()
Publication date: 11 February 2015 Source:Tetrahedron Letters, Volume 56, Issue 7 Author(s): Yadavalli Suneel Kumar , Changalaraya Dasaradhan , Kamalakannan Prabakaran , Pitchai Manivel , Fazlur-Rahman Nawaz Khan , Euh Duck Jeong , Eun Hyuk Chung A facile protocol has been developed for a series of 3-substituted isochromen-1-ones utilizing Suzuki coupling strategy. The reaction of 3-chloroisochromen-1one, 1 with different boronic acids utilizing PdCl2(PPh3)2-Ruphos catalytic system gave diversified 3-substituted isochromen-1-ones in excellent yields. The methodology has been utilized in the synthesis of glomellin and reticulol analogues. Graphical abstract image
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Synthesis, characterization, and nucleophilic ring opening reactions of cyclohexyl-substituted β-haloamines and aziridinium ions ()
Publication date: 11 February 2015 Source:Tetrahedron Letters, Volume 56, Issue 7 Author(s): Hyun-Soon Chong , Xiang Sun , Yunwei Chen , Meng Wang Cyclohexyl-substituted β-haloamines and aziridinium ions were prepared and characterized. Stereospecific ring opening of aziridinium ions was applied for efficient synthesis of vicinal amine, β-amino acid, and tetrahydroisoquinoline (THIQ) analogues. Nucleophilic ring opening reactions of aziridinium ions and N-protected aziridine analogues were for the first time comparatively studied. The result of nucleophilic reactions clearly indicates that aziridinium ions were significantly more reactive toward nucleophilic ring opening than the aziridine analogues. Graphical abstract image
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A synthesis of abemaciclib utilizing a Leuckart–Wallach reaction ()
Publication date: 11 February 2015 Source:Tetrahedron Letters, Volume 56, Issue 7 Author(s): Michael O. Frederick , Douglas P. Kjell A concise total synthesis of CDK 4/6 inhibitor abemaciclib is described. The synthesis uses a Suzuki coupling, followed by a Hartwig–Buchwald amination to join three of the four subunits. The final step is a reductive amination utilizing Leuckart–Wallach conditions. Key to the Leuckart–Wallach reaction was the addition of trimethyl orthoformate to remove water formed during the reaction, allowing the reaction to go to completion. Graphical abstract image
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Facile purification and click labeling with 2-[18F]fluoroethyl azide using solid phase extraction cartridges ()
Publication date: 11 February 2015 Source:Tetrahedron Letters, Volume 56, Issue 7 Author(s): Dong Zhou , Wenhua Chu , Xin Peng , Jonathan McConathy , Robert H. Mach , John A. Katzenellenbogen A facile method was developed to purify 2-[18F]fluoroethyl azide ([18F]FEA) using a C18 cartridge and an Oasis® HLB cartridge in series, in which [18F]FEA was exclusively trapped on the HLB cartridge. [18F]FEA can be eluted for reactions in solution; alternatively click labeling can be carried out on the HLB cartridge itself by loading an alkyne substrate and copper (I) catalyst dissolved in DMF onto the cartridge. This solid phase extraction methodology for purification and click labeling with [18F]FEA, either in solution or on the cartridge, is safe, simple, reproducible in high yield, and compatible with automated synthesis of 18F-labeled PET tracers. Graphical abstract image
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Corrigendum to “Direct synthesis of arenecarboxamides through Friedel–Crafts acylation using ureas” [Tetrahedron Lett. 55 (33) (2014) 4541–4544] ()
Publication date: 11 February 2015 Source:Tetrahedron Letters, Volume 56, Issue 7 Author(s): Weijiang Ying , Lalith S.R. Gamage , Luke R. Lovro , James W. Herndon III , Nathan W. Jenkins , James W. Herndon
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Editorial board ()
Publication date: 4 February 2015 Source:Tetrahedron Letters, Volume 56, Issue 6
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Graphical Contents List ()
Publication date: 4 February 2015 Source:Tetrahedron Letters, Volume 56, Issue 6
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Synthetic strategies for preparation of cyclen-based MRI contrast agents ()
Publication date: 4 February 2015 Source:Tetrahedron Letters, Volume 56, Issue 6 Author(s): Nevenka Cakić , Serhat Gündüz , Rathikrishnan Rengarasu , Goran Angelovski Cyclen-based macrocyclic ligands have an essential role in the development of contrast agents for magnetic resonance imaging (MRI). A prevailing need for preparation of multifunctional probes triggered a number of attempts to synthesize and derivatize ligands which efficiently chelate lanthanide ions and have advantageous MRI properties. This digest Letter summarizes the most common synthetic approaches for the preparation of macrocyclic ligands based on cyclen depending on the desired application. Graphical abstract image
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Novel and highly efficient one pot protocol for the synthesis of diversely functionalized triarylmethanes ()
Publication date: 4 February 2015 Source:Tetrahedron Letters, Volume 56, Issue 6 Author(s): B. Madhu Babu , Pramod B. Thakur , Vikas M. Bangade , H.M. Meshram An efficient, convenient, and novel one pot approach is described for the synthesis of triarylmethanes by in situ oxidation of benzylalcohols followed by the Friedel–Crafts alkylation of di/trimethoxybenzenes in the presence of BF3·OEt2. The generality of the present method is strengthened by screening a variety of aromatic, aliphatic, and heteroaromatic alcohols with methoxy arenes. Shorter reaction time, mild reaction condition, good yields, and wide scope of substrates are the significant features of this protocol. Graphical abstract image
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New short access to pyrrolo[2,3-c]pyridazin-6-ones via β-spirolactams ()
Publication date: 4 February 2015 Source:Tetrahedron Letters, Volume 56, Issue 6 Author(s): Theodor Stoll , André Alker , Sabine Kolczewski , Andrea Menzi , Vincent Revil-Baudard Treatment of 4-aminoalkyl-2,6-dichloropyridazines with acid chlorides in the presence of triethylamine leads to the formation of β-spirolactams (X-ray confirmed) which subsequently can be transformed into pyrrolo[2,3-c]pyridazin-6-ones. A putative mechanism based on the Staudinger Ketene–Imine Cycloaddition is proposed. Graphical abstract image
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Solid phase synthesis of a novel folate-conjugated 5-aminolevulinic acid methyl ester based photosensitizer for selective photodynamic therapy ()
Publication date: 4 February 2015 Source:Tetrahedron Letters, Volume 56, Issue 6 Author(s): Annalisa Guaragna , Giovanni N. Roviello , Stefano D’Errico , Concetta Paolella , Giovanni Palumbo , Daniele D’Alonzo The development of a novel tumor-targeting photosensitizer delivery system, with potential ability to selectively transport the photosensitizer prodrug 5-aminolevulinic acid methyl ester (MAL) into the tumor site has been herein described. Conjugation of MAL to folic acid (FA) via an unnatural β-peptide linker has been carried out almost entirely by an efficient solid phase approach. This molecular system has been devised for possible applications in selective photodynamic diagnosis (PDD) and therapy (PDT). Graphical abstract image
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Solvent selective phenyl selenylation and phenyl tellurylation of aryl boronic acids catalyzed by Cu(II) grafted functionalized polystyrene ()
Publication date: 4 February 2015 Source:Tetrahedron Letters, Volume 56, Issue 6 Author(s): Susmita Roy , Tanmay Chatterjee , Sk. Manirul Islam A solvent-selective methodology for the phenyl selenylation and phenyl tellurylation of aryl boronic acids has been developed for the first time using a polymer supported Cu(II) catalyst. The catalyst was synthesized by anchoring Cu(OAc)2 onto a functionalized polystyrene with pyridine thiosemicarbazone ligand. It was then characterized properly by SEM, EDAX, FT-IR, TGA, and EPR experiments. The catalyst smoothly catalyzes phenyl selenylation of aryl boronic acids in water and phenyl tellurylation of aryl boronic acids in PEG-600, selectively. Thus a wide variety of unsymmetrical organodiaryl or aryl-heteroaryl selenides and tellurides have been synthesized by this protocol. The catalyst was recycled up to six runs without any appreciable loss of catalytic activity. Graphical abstract image
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Efficient and convenient copper-free Pd(OAc)2/Ruphos-catalyzed Sonogashira coupling in the preparation of corfin analogues ()
Publication date: 4 February 2015 Source:Tetrahedron Letters, Volume 56, Issue 6 Author(s): Changalaraya Dasaradhan , Yadavalli Suneel Kumar , Kamalakannan Prabakaran , Fazlur-Rahman Nawaz Khan , Euh Duck Jeong , Eun Hyuk Chung The Sonogashira coupling reaction of 3-chloro-1H-isochromen-1-one and terminal alkynes, in the presence of catalytic system-Pd(OAc)2/Ruphos, Et3N base, and tetrahydrofuran solvent under aqueous conditions, provided novel 3-(alkynyl)-1H-isochromen-1-ones in excellent yields. The methodology has also been extended toward natural isochromen-1-ones—corfin analogues. Graphical abstract image
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Stereoselective synthesis of higher homologues of pantolactone from (R)-glyceraldehyde acetonide ()
Publication date: 4 February 2015 Source:Tetrahedron Letters, Volume 56, Issue 6 Author(s): Ishita Sanyal , Piyali Deb Barman , Asish Kumar Banerjee A stereoselective synthetic route has been developed toward the synthesis of novel γ-substituted pantolactone homologues using Sharpless asymmetric dihydroxylation of the enantiomeric alkene–ester intermediates, derived from (R)-glyceraldehyde acetonide, as the key step. Graphical abstract image
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Novel bis-calix[4]arene based molecular probe for ferric iron through colorimetric, ratiometric, and fluorescence enhancement response ()
Publication date: 4 February 2015 Source:Tetrahedron Letters, Volume 56, Issue 6 Author(s): Har Mohindra Chawla , Tanu Gupta A new bis-calix[4]arene platform (4) formed by upper rim–upper rim linking of two calixarene units has been obtained by 1:1 condensation of diformyl calixarene with carbohydrazide. The synthesized bis-calixarene has been found to selectively sense Fe3+, without interference from ferrous or any other metal ion through enhancement in the fluorescence intensity as well as ratiometric absorption changes accompanied by a color change. The importance of a bridged macro cyclic framework has been further highlighted by comparison with an acyclic reference compound. Graphical abstract image
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Photoinduced additive-free trifluoromethylation of aromatic aldehydes with TMSCF3 ()
Publication date: 4 February 2015 Source:Tetrahedron Letters, Volume 56, Issue 6 Author(s): Jing Sun , Xinhua Peng , Hao Guo We report herein a new and effective method for additive-free trifluoromethylation of aromatic aldehydes with TMSCF3. Normal acidic hydrolysis for desilylation in the workup process is not required in this transformation. This reaction presents a new environmentally friendly protocol to access trifluoromethylated benzyl alcohols. Graphical abstract image
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Rearrangement of acyclic-alkyl [3.2.1]bicyclic alcohols to free methylene dimethyl alkyl [2.2.2]bicyclic octanes: application to preparation of stereospecific novel sesquiterpene and terpenoids ()
Publication date: 4 February 2015 Source:Tetrahedron Letters, Volume 56, Issue 6 Author(s): Te-Fang Yang , Chi-Yi Chang , Wei-Fan Lin Reaction of camphor-derived [3.2.1]bicyclic hydroxyl ketone with organolithium or Grignard reagents provided various alkyl/aryl [3.2.1]bicyclic diols, in which the secondary hydroxyl group was then protected and various acetoxy [3.2.1]bicyclic alcohols were obtained. Treatment of these acetoxy [3.2.1]bicyclic alcohols with TsOH in methanol at reflux afforded various methylene dimethyl alkyl/aryl [2.2.2]bicyclic octanes. For the application of the title reaction, some of these octanes were converted to stereospecific novel sesquiterpene and terpenoids. Graphical abstract image
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Formal syntheses of (2R,3R)-3-hydroxy pipecolic acid and (2R,3S)-3-hydroxy pipecolic acid from l-ascorbic acid ()
Publication date: 4 February 2015 Source:Tetrahedron Letters, Volume 56, Issue 6 Author(s): Subhash P. Chavan , Nilesh B. Dumare , Kailash P. Pawar Formal syntheses of both cis and trans 3-hydroxy pipecolic acids is achieved from l-ascorbic acid. Present synthesis describes use of chiral pool approach in which epimerization, Staudinger reaction and Cyclization reactions were employed as key steps. Graphical abstract image
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Synthesis of 5-[3,6-di(pyridin-2-yl)pyridazine-4-yl]-2′-deoxyuridine-5′-O-triphosphate—a potential probe for fluorescence detection and imaging DNA ()
Publication date: 4 February 2015 Source:Tetrahedron Letters, Volume 56, Issue 6 Author(s): Anilkumar R. Kore , Bo Yang , Balasubramanian Srinivasan Efficient synthesis of 5-[3,6-di(pyridin-2-yl)pyridazine-4-yl]-2′-deoxyuridine-5′-O-triphosphate, a potential substrate for fluorescence detection and imaging of DNA is reported. Inverse electron demand Diels–Alder (invDA) reaction between the electron-rich 5-vinyl-2′-deoxyuridine-5′-O-triphosphate and electron-deficient tetrazine dienophile 3,6-di(pyridin-2-yl)-1,2,4,5-tetrazine resulted in the formation of 5-[3,6-di(pyridin-2-yl)pyridazine-4-yl]-2′-deoxyuridine-5′-O-triphosphate in 80% yield. This class of molecules will find applications in polymerase chain reactions for fluorescence detection and imaging applications of cellular DNA. Graphical abstract image
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Oxidative coupling of formamides with β-dicarbonyl compounds and the synthesis of 2-aminobenzothiazole using Cu(II)-functionalized Fe3O4 nanoparticles ()
Publication date: 4 February 2015 Source:Tetrahedron Letters, Volume 56, Issue 6 Author(s): Kobra Azizi , Meghdad Karimi , Akbar Heydari The Fe3O4@EDTA–Cu(II) nanoparticles catalyzed oxidative coupling of formamides with β-dicarbonyl compounds is developed using tert-butyl hydroperoxide as an oxidant. In general, the enol carbamates are synthesized in excellent yields (up to 92%) under the optimized reaction conditions. Fe3O4@EDTA–Cu(II) has the advantage of being magnetically recoverable. Also, we have established a highly efficient Fe3O4@EDTA–Cu(II)-catalyzed tandem reaction of 2-iodoanilines with isothiocyanates for the synthesis of 2-aminobenzothiazoles. Graphical abstract image
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Algiolide A, secoiridoid glucoside from Mongolian medicinal plant Gentiana algida ()
Publication date: 4 February 2015 Source:Tetrahedron Letters, Volume 56, Issue 6 Author(s): Naonobu Tanaka , Minami Takekata , Shin-ichiro Kurimoto , Kazuyoshi Kawazoe , Kotaro Murakami , Davaadagva Damdinjav , Enkhjargal Dorjbal , Yoshiki Kashiwada A new secoiridoid glucoside, algiolide A (1), was isolated from the aerial parts of a Mongolian traditional herbal medicine Gentiana algida (Gentianaceae). The structure of 1 was elucidated on the basis of spectroscopic analysis and chemical conversion as well as calculations of NMR and ECD spectra. Algiolide A (1) has a novel skeleton consisting of fused α,β-unsaturated-δ-lactone and cyclopentene rings. Graphical abstract image
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Aromatic plane effect study in pseudorotaxane construction between ‘Texas-sized’ molecular box and carboxylate anions ()
Publication date: 4 February 2015 Source:Tetrahedron Letters, Volume 56, Issue 6 Author(s): Feng Tang , Rui Cao , Han-Yuan Gong This study focused on the aromatic plane effect of the binding modes between ‘Texas-sized’ molecular box and carboxylate anion species. The molecular box, namely cyclo[2](2,6-di(1H-imidazol-1-yl)pyridine)-[2](1,4-dimethylenebenzene) (1 4+; studied as the PF6 − salt), easily constructs interpenetrated structures (i.e., pseudorotaxanes) with carboxylate anions via the introduction of aromatic rings. As revealed by 1H NMR titration, two-dimensional nuclear Overhauser effect spectroscopy (NOESY), UV–Vis spectroscopic study, and electrospray ionization mass spectrometry (ESI-MS), the determination effect of aromatic plane in the binding modes between 1 4+ and carboxylate anions was studied in detail. This research reveals the important role of aromatic plane substitute groups on anions for building anion-induced interpenetrated self-assembly structures. Graphical abstract image
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Fluorinated perylene diimides: synthesis, electrochemical–photophysical properties, and cellular imaging ()
Publication date: 4 February 2015 Source:Tetrahedron Letters, Volume 56, Issue 6 Author(s): Jia Wang , Shilong Zhong , Wenfeng Duan , Baoxiang Gao We report the synthesis and properties of perylene diimides with fluorinated substituents on the bay (BFPDIs). These BFPDIs exhibit good water solubility, high extinction coefficients, and high fluorescence quantum yields. Furthermore, these BFPDIs are used as probes in cellular imaging. Graphical abstract image
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A comparative synthesis of 6-benzyl-2,3-dihydroimidazo[2,1-a]phthalazine and 2H-7-benzyl-3,4-dihydropyrimido[2,1-a]phthalazine ()
Publication date: 4 February 2015 Source:Tetrahedron Letters, Volume 56, Issue 6 Author(s): Javier Munín , Lourdes Santana , Eugenio Uriarte , Fernanda Borges , Elías Quezada Two new synthetic strategies have been developed for the synthesis of a new class of cyclophthalazine derivatives. 6-Benzyl-2,3-dihydroimidazo[2,1-a]phthalazine and 2H-7-benzyl-3,4-dihydropyrimido[2,1-a]phthalazine were obtained (i) by intramolecular cyclization of the 2-(aminoalkyl)-4-benzyl-2H-phthalazin-1-one or (ii) by intramolecular cyclization of the corresponding 2-(4-benzylphthalazin-1(2H)-ylideneamino)alcohols previously prepared. The second of the described routes afforded the desired derivatives in high yields. Graphical abstract image
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Copper-catalyzed oxidative amidation between aldehydes and arylamines under mild conditions ()
Publication date: 4 February 2015 Source:Tetrahedron Letters, Volume 56, Issue 6 Author(s): Yongzheng Ding , Xian Zhang , Dongyang Zhang , Yuting Chen , Zhibing Wu , Peiyi Wang , Wei Xue , Baoan Song , Song Yang A facile strategy to prepare amide bonds has been developed. A series of amide compounds, including heterocyclic amide compounds, were obtained with moderate to good yields ranging from 31–88% by using copper iodide (CuI) to catalyze the oxidative amidation between aldehydes and amines under solvent-free conditions at room temperature in air. Graphical abstract image
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A stereoselective approach for the total synthesis of (−)-tadanalactam from acetonide-d-glucose ()
Publication date: 4 February 2015 Source:Tetrahedron Letters, Volume 56, Issue 6 Author(s): Saidulu Konda , Bhaskar Kurva , Lingaiah Nagarapu , Akkewar M. Dattatray A stereoselective and realistic approach for the total synthesis of naturally occurring δ-lactam (−)-tadanalactam, has been accomplished from the commercially existing acetonide-d-glucose involving Birch reduction, Pinnick oxidation, Staudinger reaction, and hydroboration reactions. Finally benzyl ether deprotection and subsequent oxirane formation using Birch reduction completed the total synthesis of (−)-tadanalactam. Graphical abstract image
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An atom-economic green approach: oxidative synthesis of functionalized 1,4-dihydropyridines from N,N-dimethylenaminones and amines ()
Publication date: 4 February 2015 Source:Tetrahedron Letters, Volume 56, Issue 6 Author(s): Fu-Chao Yu , Bei Zhou , Hui Xu , Kwen-Jen Chang , Yuehai Shen We report the first oxidative condensation between N,N-dimethylenaminones with amines to form 1,4-dihydropyridines in moderate to good yields, promoted by oxone and trifluoroacetic acid in PEG-400. This reaction features an unusual oxidation of in situ formed dimethylamine to efficiently provide the 4-methylene of 1,4-dihydropyridines, and a highly environment-friendly reaction condition. Graphical abstract image
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First examples of 2,6-diarylnicotinaldehydes prepared under conventional and microwave conditions ()
Publication date: 4 February 2015 Source:Tetrahedron Letters, Volume 56, Issue 6 Author(s): K. Shankaraiah , G. Chandrasekhar , K. Siva Nagi Reddy , Gowravaram Sabitha Enaminoketones undergo unexpected self condensation in acetic acid to produce a wide range of 2,3,6-trisubstituted pyridine derivatives in excellent yields in the presence of NH4OAc. This is the first Letter on the synthesis of 2,6-diarylnicotinaldehydes. The reaction was studied under microwave irradiation and conventional heating. However, mixed condensations were observed when two different enaminones are combined. Graphical abstract image
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Microwave-assisted synthesis of xanthones promoted by ytterbium triflate ()
Publication date: 4 February 2015 Source:Tetrahedron Letters, Volume 56, Issue 6 Author(s): Salvatore Genovese , Serena Fiorito , Maria Carmela Specchiulli , Vito Alessandro Taddeo , Francesco Epifano Xanthones represent a class of naturally occurring compounds with valuable and promising reported pharmacological activities. One of the main disadvantages in the use of such products is related to the difficulties in their chemical synthesis. In this Letter a new and improved method for the chemical synthesis of xanthones is described. The title compounds have been synthesized in good yields under microwave irradiation from substituted 2-hydroxybenzoic acids and phenols in the presence of Yb(OTf)3 hydrate as the catalyst. Graphical abstract image
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Palladium-catalyzed ortho-arylation of benzoic acid derivatives via C–H bond activation using an aminoacetic acid bidentate directing group ()
Publication date: 4 February 2015 Source:Tetrahedron Letters, Volume 56, Issue 6 Author(s): Xiaomeng Zhou , Qing Wang , Weihua Zhao , Songsong Xu , Wei Zhang , Junmin Chen A highly efficient protocol for the palladium-catalyzed ortho-arylation of benzoic acid derivatives by aryl iodides is described with an aminoacetic acid based N,O bidentate directing group. This protocol can be applied to various benzoyl aminoacetic acids and aryl iodides with both electron-donating and electron-withdrawing groups. Remarkably, the nature of a new directing group drives selective C–H bond activation to afford only monoarylation products in good to excellent yields. Graphical abstract image
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N-Methylative aziridine ring opening: asymmetric synthesis of hygroline, pseudohygroline, and hygrine ()
Publication date: 4 February 2015 Source:Tetrahedron Letters, Volume 56, Issue 6 Author(s): Jaedeok Lee , Jae Eun Lee , Hyun-Joon Ha , Se In Son , Won Koo Lee Asymmetric syntheses of biologically and pharmaceutically important (−)-hygroline, (−)-pseudohygroline, and (−)-hygrine were achieved by a newly developed ‘N-methylative aziridine ring opening reactions’ of (2S)-methoxycarbonylethylaziridine as a key step. Graphical abstract image
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p-Toluenesulfonic acid doped polystyrene (PS-PTSA): solvent-free microwave assisted cross-coupling-cyclization–oxidation to build one-pot diversely functionalized pyrrole from aldehyde, amine, active methylene, and nitroalkane ()
Publication date: 4 February 2015 Source:Tetrahedron Letters, Volume 56, Issue 6 Author(s): Vijay Vilas Shinde , Sang Dong Lee , Yong Seok Jeong , Yeon Tae Jeong A solvent-free environmentally benign approach for the synthesis of diversified pyrrole derivatives has been described by the one-pot multicomponent reaction of aldehydes, nitroalkane, amine, and enolizable active C–H reactant using polystyrene supported p-toluenesulfonic acid (PS-PTSA) under microwave irradiation. In comparison to the conventional methods, this efficient green protocol provides remarkable advantages such as good to excellent yields, shorter reaction time, low cost, easy work-up procedure, and bypass for use of hazardous transition metal catalyst and organic solvent. Graphical abstract image
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Novel supramolecular liquid crystals: synthesis and mesomorphic properties of calix[4]arene-cholesterol derivatives ()
Publication date: 4 February 2015 Source:Tetrahedron Letters, Volume 56, Issue 6 Author(s): Hongyu Guo , Fafu Yang , Weiwei Liu , Jianbin Lai The first calix[4]arene-cholesterol liquid crystals were designed and synthesized in yields of 50–80%. Structural and conformational characterization of these new compounds had been achieved by NMR, MS, and elemental analysis. Their liquid crystalline behaviors were studied by polarizing optical microscopy, differential scanning calorimetry, and X-ray diffraction. All calix[4]arene derivatives with two or four cholesterol units show excellent mesomorphic properties of the columnar molecular arrangement of the calixarenes bowlic columns with cholesterol units as ancillary lateral columns. The long spacer and more cholesterol units were favorable for excellent mesophase. Graphical abstract image
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