Rh-Catalyzed Regioselective Dialkylation of Cage B–H bonds in o-Carboranes: Oxidative Heck Reactions via an Enol Isomerization

Abstract

In the presence of a carboxylic acid directing group, Rh-catalyzed regioselective directed dialkylation of B(4,5)-H bonds in <i>o-</i>carboranes and oxidative coupling with allylic alcohols is reported. This strategy constructs a series of 4,5-dialkylated <i>o</i>-carboranes in good yields with excellent regioselectivity. A possible catalytic cycle is proposed that involves a tandem sequence of Rh-catalyzed cage B-H activation, alkene insertion, selective β-H elimination, enol isomerization, and decarboxylation.