نتایج جستجو برای: stereoselectivity
تعداد نتایج: 1551 فیلتر نتایج به سال:
A novel phosphine-catalyzed intermolecular [3 + 2] cycloaddition of ynones and N-substituted isatins was developed. In this reaction, substituted ynones, serving as a C(3) synthon, were successfully applied in intermolecular annulation reactions. A number of functionalized spirooxazolines were obtained in high yields and stereoselectivity.
A rhodium-catalyzed intermolecular hydroarylation of internal alkynes with N-1-phenylbenzotriazoles via C-H bond activation is described. This transformation offers an alternative method for the hydroarylation of internal alkynes with high stereoselectivity. The reaction mechanism was discussed according to the deuterium-labeling experiments.
Stabilized AlHCl(2)·(THF)(2) hydroaluminates RC≡CH with exceptional chemo-, regio- and stereoselectivity under efficient ZrCl(2)(η-C(5)Me(5))(2) catalysis (2-5 mol%). The resulting vinyl alanes undergo palladium cross-coupling with a wide range of sp(2) electrophiles (aryl, heteroaryl and vinyl halides/pseudohalides) in good to excellent yields.
Wild-type Candida tenuis xylose reductase and two Trp-23 mutants thereof catalyze NADH-dependent reduction of a homologous series of aromatic alpha-keto esters with absolute pseudo re-face stereoselectivity and broad tolerance for the substituent on the aromatic ring, producing the corresponding R-alcohols in high yield.
Based on consecutive one-pot conditions combining three palladium-catalyzed reactions (Sonogashira, Heck and Suzuki-Miyaura reactions), a more efficient domino multicomponent method has been successfully developed to access a wide variety of 3-(diarylmethylene)oxindoles. Microwave irradiation and use of a silver salt were the most important factors to achieve high yields and stereoselectivity.
A novel method for the synthesis of vinyl sulfides by the decarboxylative cross-coupling of arylpropiolic acids with thiols using copper(I) salts as catalysts has been developed. In the presence of CuI and Cs(2)CO(3), a variety of thiols reacted with arylpropiolic acids to afford the corresponding vinyl sulfides in good to excellent yields with high stereoselectivity for Z-isomers.
A total synthesis of paroxetine is reported, with a diastereoselective and diastereoconvergent cobalt-catalysed sp3-sp2 coupling reaction involving a 3-substituted 4-bromo-N-Boc-piperidine (Boc = tert-butoxycarbonyl) substrate as a key step. A 9:1 diastereoselectivity was obtained, while a control experiment involving a conformationally locked 3-substituted 4-bromo-tert-butyl cyclohexane ring p...
The cyclization of 2,5-cyclohexadienones tethered to activated methylene groups was studied. The substitution around the cyclohexadienone ring serves to regioselectively direct these cyclizations based primarily on electronic effects. In the case of brominated substrates, these reactions proceed to give highly unusual electron-deficient tricyclic cyclopropanes. By using a Cinchona alkaloid-base...
A wide variety of chiral succinimides have been prepared in high yields and enantioselectivities by an asymmetric conjugate addition of 1,3-dicarbonyl compounds to maleimides under very mild reaction conditions using the bifunctional benzimidazole-derived organocatalyst 5f. Computational and NMR studies support the hydrogen-bonding activation role of the catalyst and the origin of the stereosel...
A broad range of readily accessible N-sulfonyl imines undergo olefination reaction with nonstabilized phosphonium ylides under mild conditions to afford an array of both Z- and E-isomers of 1,2-disubstituted alkenes, allylic alcohols, and allylic amines in good yields and with greater than 99 : 1 stereoselectivity.
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