Negishi Ei-Ichi, Tobrman Tomas, Rao Honghua, Xu Shiqing, Lee Ching-Tien
Herbert C. Brown Laboratories of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, Indiana 47907-2084, USA.
Isr J Chem. 2010 Dec 1;50(5-6):696-701. doi: 10.1002/ijch.201000051.
()--bromo-1-propenyl(pinacol)borane(), recently made available in 85% yield as a ≥98% isomerically pure compound via bromoboration of 1-propyne, has been converted to alkyl-, aryl-, and alkenyl-substituted ()-2-methyl-1-alkenyl(pinacol)boranes() in ca. 75% yield based on propyne via Pd-catalyzed Negishi alkenylation with suitable organozinc bromide. The previously sluggish and modest-yielding Suzuki alkenylation of ,-disubstituted alkenylboranes has been significantly promoted by fluorides, especially BuNF(TBAF) or CsF to give trisubstituted alkenes, i.e., ()--Me-substituted -- and ()--Ph-substituted and . In all cases, each alkene product was formed in a ≥98% seteoselectivity. The propyne-based protocol nicely complements the widely used Zr-catalyzed alkyne methylalumination-Pd-catalyzed alkenylation by providing a highly stereoselective(≥98%) route to ()-Me-substituted alkenes.
（）-溴-1-丙烯基（频哪醇）硼烷（），最近通过1-丙炔的硼溴化反应以85%的产率得到了一种≥98%的异构体纯化合物，通过与合适的有机溴化锌进行钯催化的根岸烯基化反应，已以基于丙炔约75%的产率转化为烷基、芳基和烯基取代的（）-2-甲基-1-烯基（频哪醇）硼烷（）。氟化物，特别是BuNF（TBAF）或CsF显著促进了先前缓慢且产率适中的，-二取代烯基硼烷的铃木烯基化反应，得到三取代烯烃，即（）- - 甲基取代的 - - 和（）- - 苯基取代的 - - 和 - - 。在所有情况下，每种烯烃产物的形成立体选择性均≥98%。基于丙炔的方法通过提供一条通往（）-甲基取代烯烃的高立体选择性（≥98%）路线，很好地补充了广泛使用的锆催化炔烃甲基铝化 - 钯催化烯基化反应。
