The application of the shapiro reaction to the stereoselective synthesis of E-trisubstituted olefins for cation-olefin cyclization by three component coupling
摘要:
A method is described for the rapid and stereoselective assembly of E-trisubstituted olefins by a convergent process from three components. (C) 1997 Elsevier Science Ltd.
Electrophilic Cleavage of Cyclopropylmethystannanes: An Experimental Comparison of σ−σ and σ−π Conjugation
作者:Andrew J. Lucke、David J. Young
DOI:10.1021/jo047822p
日期:2005.4.1
Cyclopropylmethyltrimethylstannanes undergo electrophiliccyclopropanecleavage in chloroform with simple inorganic electrophiles (H+, SO2, I2) in a homologous reaction to the SE‘ cleavage of allylic stannanes. The σ−σ conjugation between the carbon−tin bond and cyclopropane orbitals observed spectroscopically in the parent cyclopropylmethyltrimethylstannane is responsible for a rate enhancement of
环丙基甲基三甲基锡烷酮与简单的无机亲电试剂(H +,SO 2,I 2)在氯仿中进行亲电环丙烷裂解,与烯丙基锡烷的S E '裂解发生同源反应。在母体环丙基甲基三甲基锡烷中通过光谱观察到的碳-锡键与环丙烷轨道之间的σ-σ共轭可提高ca的速率。相对于可比较的烷基锡烷,10 2趋向碘解。但是,该加速度远小于约1。10 9烯丙基锡烷中相应的σ-π共轭提供的倍数速率增强。甲醇-锡配位似乎减少了金属的活化作用,从而促进了在环丙烷裂变中用酸和碘进行甲基裂解。降低的σ-σ共轭也可以解释与三甲基锡对应物相比环丙基三苯基锡烷的反应性降低。在促进烯丙基锡烷的相应反应的条件下,环丙基甲基锡烷不经过合成有用的醛加成。
Studies of Intramolecular Cyclizations of <i>N</i>-Acyliminium Ions Derived from Acyclic Ketones: Unanticipated Stereochemical and Structural Results
作者:Wenchun Chao、Jacob H. Waldman、Steven M. Weinreb
DOI:10.1021/ol035046m
日期:2003.8.1
[reaction: see text] Intramolecular cyclizations of a series of (E)- and (Z)-olefinic acyclic ketone-derived N-acyliminium ions have been studied. It has been found that both the course of the reaction and the stereochemistry of the products are critically dependent upon the tether length and olefin geometry of the cyclization substrate.
The synthetic approach to the core framework of daphniglaucin-type Daphniphyllum alkaloids is described herein. The B–C ring was constructed via a Rh-catalyzed [3+2] cycloaddition. Continuous quaternary centers were installed through [3+2] cycloaddition and alkylation. The attempt to build the A–D ring motif using dipolar cycloaddition of azomethine ylides was extensively investigated.