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Chinmay Chowdhury Kaushik Brahma Sanjukta Mukherjee Anup Kumar Sasmal 《Tetrahedron letters》2010,51(21):2859-5511
A new, one-pot palladium catalyzed reaction has been developed for the general synthesis of (E)-3-arylidene-3,4-dihydro-2H-1,4-benzoxazines at room temperature. The reaction procedure tolerates various functional groups. The method is characterized by regio- and stereoselectivity, operational simplicity, mild reaction conditions, and short reaction time. 相似文献
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The chemical synthesis of a pentasaccharide and a hexasaccharide corresponding to the O-antigen of Escherichia coli O150 has been achieved using sequential glycosylation and [3+3] block glycosylation strategies. Suitably protected monosaccharide synthons have been prepared from the commercially available reducing sugars and then stereoselectively coupled to give the pentasaccharide and a hexasaccharide in excellent yields. 4-Methoxyphenyl and 2-(4-methoxyphenoxy) ethyl groups have been used as the anomeric-protecting groups in the target pentasaccharide and a hexasaccharide, respectively. 相似文献
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Song Y Yang Y Medforth CJ Pereira E Singh AK Xu H Jiang Y Brinker CJ van Swol F Shelnutt JA 《Journal of the American Chemical Society》2004,126(2):635-645
Seeding and autocatalytic reduction of platinum salts in aqueous surfactant solution using ascorbic acid as the reductant leads to remarkable dendritic metal nanostructures. In micellar surfactant solutions, spherical dendritic metal nanostructures are obtained, and the smallest of these nanodendrites resemble assemblies of joined nanoparticles and the nanodendrites are single crystals. With liposomes as the template, dendritic platinum sheets in the form of thin circular disks or solid foamlike nanomaterials can be made. Synthetic control over the morphology of these nanodendrites, nanosheets, and nanostructured foams is realized by using a tin-porphyrin photocatalyst to conveniently and effectively produce a large initial population of catalytic growth centers. The concentration of seed particles determines the ultimate average size and uniformity of these novel two- and three-dimensional platinum nanostructures. 相似文献
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Dr. Suman De Sarkar Anup Biswas Ramesh C. Samanta Prof. Dr. Armido Studer 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(15):4664-4678
This Concept article discusses the potential of oxidative carbene catalysis in synthesis and comprehensively covers pioneering studies as well as recent developments. Oxidative carbene catalysis can be conducted by using inorganic and organic oxidants. Applications in cascade processes, in enantioselective catalysis, and also in natural product synthesis are discussed. 相似文献
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Electrophile‐Induced Nucleophilic Substitution of the nido‐Dicarbaundecaborate Anion nido‐7,8‐C2B9H12− by Conjugated Heterodienes
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Dr. René Frank Anup Kumar Adhikari Henry Auer Prof. Dr. Evamarie Hey‐Hawkins 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(5):1440-1446
Substitution of the dicarbaundecaborate anion nido‐7,8‐C2B9H12? ( 1 ) by precise hydride abstraction followed by nucleophilic attack usually leads to symmetric products 10‐R‐nido‐7,8‐C2B9H11. However, thioacetamide (MeC(S)NH2) as nucleophile and acetone/AlCl3 as hydride abstractor gave asymmetric 9‐[MeC(NHiPr)S]‐nido‐7,8‐C2B9H11 ( 2 ), whereas N,N‐dimethylthioacetamide (MeC(S)NMe2) gave the expected symmetric 10‐[MeC(NMe2)S]‐nido‐7,8‐C2B9H11 ( 4 ). For the formation of 2 , acetone and thioacetamide are assumed to give the intermediate MeC(S)N(CMe2) ( 3 ), which then attacks 1 with formation of 2 . Similarly, reaction of acetyliminium chloride [MeC(O)NH(CPh2)]Cl ( 5 ) with 1 in THF gave a mixture of 9‐ and 10‐substituted [MeC(NHCHPh2)O]‐nido‐7,8‐C2B9H11 ( 6 and 7 , respectively). These reactions are the first examples in which compounds (here heterodienes) that unite the functionalities of both hydride acceptor and nucleophilic site react with 1 in a bimolecular fashion. Furthermore, the analogous reaction of 1 and 5 (in an equilibrium mixture with acetyl chloride and benzophenone imine) in MeCN afforded 10‐[MeC(NCPh2)NH]‐nido‐7,8‐C2B9H11 ( 8 ) and MeC(O)NHCHPh2 ( 9 ). 相似文献