an efficient asymmetric denitrogenative cycloaddition of benzotriazoles with cyclic and acyclic 1,3-dienes enabled by Pd and chiral sulfonamide phosphine ligand. A variety of substituted hexahydrocarbazoles and indolines were delivered in good yields with high ee values. Interestingly, a pair of enantiomers could be obtained with the use of Xu1 and PC2 with the same absolute configuration. The synthetic
不对称脱氮环加成已成为构建手性氮杂杂环的有力工具。然而,迄今为止,仅探索了苯并三唑与不饱和烃的不对称脱氮环加成的一个例子,因为苯并三唑开环生成α-亚氨基金属类卡宾是一种热力学不利的过程。我们在此报告了由 Pd 和手性磺酰胺膦配体实现的苯并三唑与环状和非环状 1,3-二烯的有效不对称脱氮环加成反应。各种取代的六氢咔唑和二氢吲哚均以良好的收率和高 ee 值交付。有趣的是,使用Xu1和PC2可以获得一对对映异构体具有相同的绝对配置。还展示了光学活性六氢咔唑的合成效用。
Enantioselective Radical Carbocyanation of 1,3-Dienes via Photocatalytic Generation of Allylcopper Complexes
1,3-Dienes are readily available feedstocks that are widely used in the laboratory and industry. However, the potential of converting 1,3-dienes into value-added products, especially chiral products, has not yet been fully exploited. By synergetic photoredox/copper catalysis, we achieve the first visible-light-induced, enantioselective carbocyanation of 1,3-dienes by using carboxylic acid derivatives
Sulfur as a Bridge: Synthesis of Medium Rings via a Bicyclic Sulfonium Ion
作者:Hongwei Zhou、Yanpeng Xing、Le Liu、Junjie Hong
DOI:10.1002/adsc.201100502
日期:2011.11
A facile and efficient synthesis of medium rings via a bicyclic sulfonium ion was developed. Spectroscopic evidence for the formation of an intermediate sulfonium moiety is provided. The sulfur atom served as a “bridge” to access the medium ring system and could be removed after use via a Ramberg–Bäcklund process. As a result of the readily available starting materials, simple operation, and mild conditions
Stereoselective ultrasonically induced reductive monosilylation of geminal dibromonorcaranes. Steric effects
作者:Brian C Raimundo、Albert J Fry
DOI:10.1016/s0022-328x(99)00146-1
日期:1999.7
Sonochemical reductive silylation of 1-R-7,7-dibromonorcaranes (R = H, Me, Et, i-Pr) by magnesium produces in each case two 7-bromo-7-trialkylsilylnorcaranes (alkyl = methyl or ethyl). The major isomer is exo (the trialkylsilyl group is cis to the R substituent), but the stereoselectivity of silylation decreases as the alkyl group size at C-l increases, 1-Phenyl-7,7-dibromonorcarane produced a mixture of phenylcycloheptadienes and monobromonorcaranes. (C) 1999 Elsevier Science S.A. All rights reserved.
Conversion of allyl alcohols to 1,3-dienes by sequential sulfenate sulfoxide [2,3]-sigmatropic rearrangement and syn-elimination