One-pot synthesis of 1-aryl-3-methyl-1,3-dienes using methallyl(trimethyl)silane and aldehydes and their low temperature (Z)→(E) isomerization induced by sulfur dioxide
摘要:
2-Methylprop-2-ene-1-sulfonyl fluorides can be easily prepared via the ene reaction of methallylsilanes and SO2. In the presence of a base, aldehydes and 2-methylprop-2-ene-1-sulfonyl fluorides give 1.3-(E) and (Z)-dienes. Their (Z) --> (E) isomerization by classical means fails or leads to their polymerization. It is shown that SO, can isomerize 1-aryl-3-methyl-1.3-dienes at low temperature, without formation of sulfolenes (cheletropic addition/elimination). Preliminary mechanistic studies suggest that SO2 adds to 1.3-dienes forming 1,4-diradical intermediates that are responsible for the (Z)-->(E) isomerizations. (C) 2004 Elsevier Ltd. All rights reserved.
Catalyst-Controlled Regioselectivity in the Synthesis of Branched Conjugated Dienes via Aerobic Oxidative Heck Reactions
作者:Changwu Zheng、Dian Wang、Shannon S. Stahl
DOI:10.1021/ja307371w
日期:2012.10.10
Pd-catalyzed aerobic oxidative coupling of vinylboronic acids and electronically unbiased alkyl olefins provides regioselective access to 1,3-disubstituted conjugateddienes. Catalyst-controlled regioselectivity is achieved by using 2,9-dimethylphenanthroline as a ligand. The observed regioselectivity is opposite to that observed from a traditional (nonoxidative) Heck reaction between a vinyl bromide
Pd 催化的乙烯基硼酸和电子无偏烷基烯烃的有氧氧化偶联提供了对 1,3-二取代共轭二烯的区域选择性访问。催化剂控制的区域选择性是通过使用 2,9-二甲基菲咯啉作为配体来实现的。观察到的区域选择性与从溴乙烯和烯烃之间的传统(非氧化)Heck 反应观察到的相反。DFT 计算研究表明,2,9-二甲基菲咯啉配体的空间效应促进了烯烃内部位置的 CC 键形成。
Asymmetric Assemblies of 1,3-Dienes, Sulfuric Diamide, and Aldehydes to Access 1,3-Diamines through Relay Amine/Palladium Catalysis
A relaycatalytic protocol using pyrrolidine and palladium catalysis has been developed for asymmetric synthesis of 1,3-diamine derivatives from 3-substituted 1,3-dienes, sulfuric diamide, and aldehydes. This one-pot, three-component reaction features the advantages of a high atom step economy and operational simplicity, providing an efficient and straightforward access to valuable 1,3-diamines incorporating