Carboindation of Alkynes. Regio- and Stereoselective Allylation of Carbon-Carbon Triple Bonds of Alkynols by Allylic Indium Reagents
作者:Shuki Araki、Akira Imai、Ken Shimizu、Masafumi Yamada、Akihiro Mori、Yasuo Butsugan
DOI:10.1021/jo00111a049
日期:1995.3
Allylindium sesquihalides undergo smooth allylindation with terminal alkynes bearing a neighboring hydroxyl group at 100-140 degrees C to give allylalkenols. The coupling occurred regioselectively at the gamma-carbon of the allylindium reagents via syn-addition, whereas the regioselectivity concerning the alkynol depends upon the structures of both allylindium and alkynol. The allylation of nonfunctionalized alkynes is less efficient, requiring higher reaction temperature (150-180 degrees C) and giving lower yields. Mechanistic considerations suggest a hydroxyl-assisted concerted process for the allylindation of alkynols, whereas a radical pathway is more likely for nonfunctionalized alkynes. Three monoterpene alcohols, i.e., yomogi alcohol, achillenol, and isomyrcenol, were conveniently prepared via allylindation of appropriate alkynols.