Generation of Allenic/Propargylic Zirconium Complexes and Subsequent Cross-Coupling Reactions: A Facile Synthesis of Multisubstituted Allenes
作者:Hao Zhang、Xiaoping Fu、Jingjin Chen、Erjuan Wang、Yuanhong Liu、Yuxue Li
DOI:10.1021/jo9020419
日期:2009.12.18
The β-alkoxide elimination reaction of propargylic ether with Negishi reagent leads to allenes and/or alkynes after hydrolysis. The product distribution is highly dependent on the substitution pattern of starting propargylic ethers; that is, aryl- or alkyl-substituted propargylic ethers favor the allene products, whereas TMS-substituted propargylic ethers afford alkynes. DFT calculations revealed that
炔丙基醚与Negishi试剂的β-醇盐消除反应在水解后会生成丙二烯和/或炔烃。产物的分布高度取决于起始炔丙基醚的取代方式。也就是说,芳基或烷基取代的炔丙基醚有利于丙二烯产物,而TMS取代的炔丙基醚则可提供炔烃。DFT计算显示,TMS组的大位阻效应和β效应均有利于炔烃产物,从而逆转了选择性。烯丙基/炔丙基锆中间体与芳基碘化物在Pd(PPh 3)4 / CuCl存在下的随后偶联反应为合成多取代的烯烯提供了一条直接途径。