Allenylation and propargylation reactions of ketones, aldehydes, imines, and iminium ions using organoboronates and related derivatives

Allenyl- and propargylboronates have emerged as versatile reagents to effect regioselective propargylation or allenylation reactions of aldehydes, ketones, imines, and iminium ions. These boron-­derived reagents have the ability to undergo transmetalation reactions with other metals (Ag, Cu, In, and Zn), often using only catalytic amounts of these metals, leading to more facile and highly regioselective reactions. Enantioselective organocatalyzed reactions have also been developed using, chiral diols, aminophenols, and phosphoric ­acids. This short review highlights recent developments in this area.