Carboindation of Alkynes. Regio- and Stereoselective Allylation of Carbon-Carbon Triple Bonds of Alkynols by Allylic Indium Reagents

Article abstract of DOI:10.1021/jo00111a049

Allylindium sesquihalides undergo smooth allylindation with terminal alkynes bearing a neighboring hydroxyl group at 100-140 deg C to give allylalkenols.The coupling occurred regioselectively at the γ-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 deg 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.