Magnesium-mediated hydroboration under ambient condition: A reduction of esters, aldehydes, and ketones

Alkoxymagnesium halide is demonstrated as an effective catalyst for the carbonyl hydroboration of esters, aldehydes, and ketones. This study reports the smooth hydroboration of a variety of esters, aldehydes, and ketones with ethoxymagnesium chloride (EtOMgCl) and pinacolborane under mild reaction conditions (low catalyst loading 0.3 mol% for aldehydes and ketones, 5 mol% for esters, room temperature). Among the tested alkoxymagnesium chlorides, EtOMgCl was the optimum catalyst in terms of yield and selectivity for esters. Moreover, the designed protocol afforded the chemoselective hydroboration of esters in good yields with high selectivity.