The first N,N′-ditosyl-substituted cyclic boron cation, stabilized by neighboring-group participation by two sulfonyl groups, and the alternative, stabilized by polar solvents
摘要:
When 2-bromo-1,3-ditosyl-1,3,2-diazaborolidine was treated with AgSbF6, a novel cyclic boron cation was formed in CD2Cl2, the B-11 NMR chemical shift of which appeared at 8.7ppm. Ab initio calculations were consistent with the cationic boron center being stabilized by neighboring-group participation of the two sulfonyl functions. The reaction in CD3NO2, resulted in art alternate formation of a cyclic boron cation species (16.2ppm), stabilized by coordination to the basic solvents. (C) 2004 Elsevier Ltd. All rights reserved.
A practical and efficient method for enantioselective allylation of aldehydes
作者:E. J. Corey、Chan Mo Yu、Sung Soo Kim
DOI:10.1021/ja00196a082
日期:1989.7
La reaction d'(allyl-2 diphenyl-4,5 ditosyl-1,3)diazaborolidines-1,3,2 chirales avec des aldehydes fournit des alcools homoallyliques de maniere enantioselective
La 反应 d'(allyl-2 diphenyl-4,5 ditosyl-1,3)diazaborolidines-1,3,2 手性 avec des aldehydes Fournit des alcools homoallyliques de maniere enantioselective
Lewis Acid Mediated Asymmetric [2,3]-Sigmatropic Rearrangement of Allylic Amines. Scope and Mechanistic Investigation
The first asymmetric [2,3]-sigmatropicrearrangement of achiral allylic amines has been realized by quaternization of the amines with an enantiomerically pure diazaborolidine and subsequent treatment with Et3N. The resultant homoallylic amines were obtained in good yields and excellent ee's. The observed diastereo- and enantioselectivities were rationalized by invoking a kinetically controlled process
with aldehydes to provide an α- or γ-adduct depending on the aldehyde pair is reported. In most cases, except enals, a mixture of a chiral bromoborane with 2-alkyl allenoates in the presence of iPr2NEt can react with aldehydes to provide efficient γ-addition products as single isomers containing axial and central chirality. On the other hand, observations indicate that enals undergo α-addition to yield
The synthesis of the C1–C27 fragment of hemicalide, a marinemetabolite displaying a unique potent antiproliferative activity, has been accomplished. The synthetic approach highlights a remarkably efficient ring-closing metathesis reaction catalyzed by Nolan ruthenium indenylidene complexes to elaborate the highly substituted δ-lactone framework.
Stereocontrol in Asymmetric S<sub>E</sub>′ Reactions of γ-Substituted α,β-Unsaturated Aldehydes
作者:David R. Williams、Bruce A. Atwater、Seth A. Bawel、Pucheng Ke、Osvaldo Gutierrez、Dean J. Tantillo
DOI:10.1021/ol403351x
日期:2014.1.17
Asymmetric SE′ reactions of (E)- and (Z)-γ-substituted-α,β-unsaturated aldehydes have been studied for the stereocontrolled preparation of nonracemic alcohols. Mild exchange reactions of allylic stannanes provide access to chiral 1,3-bis(tolylsulfonyl)-4,5-diphenyl-1,3-diaza-2-borolidines. These reagents display reactivity with the γ-substituted α,β-unsaturated aldehydes, which is characterized by
已经研究了(E)-和(Z)-γ-取代的α,β-不饱和醛的不对称S E '反应,用于立体控制非外消旋醇的制备。烯丙基锡烷的温和交换反应可提供手性1,3-双(甲苯磺酰基)-4,5-二苯基-1,3-二氮杂-2-硼烷核苷。这些试剂与γ-取代的α,β-不饱和醛具有反应性,其特征在于立体控制的元素匹配和错配。计算分析(使用密度泛函理论)提供了宝贵的见识,可指导反应的发展。