Practical Synthesis of Chiral Allylboronates by Asymmetric 1,1-Difunctionalization of Terminal Alkenes.

We report herein a modular catalytic method for the efficient enantioselective synthesis of chiral allylboronates from abundant feedstock chemicals through an asymmetric 1,1-difunctionalization of alkenes. This protocol is distinguished by its use of an inexpensive chiral catalyst, mild and convenient reaction conditions, wide substrate scope, scalability and practicality. The utility of this method is demonstrated by the rapid synthesis of key intermediates of complex drug molecules. Mechanistic studies reveal that β-H elimination is a highly regioselective step and the reversible homolysis and convergance to the lower energy pre-reductive elimination intermediate is the enantio-determining step.