Lithium diisobutyl-tert-butoxyaluminum hydride promoted ester hydroboration: An efficient protocol under solvent-free conditions at room temperature

Abstract

Ester-to-alcohol reductions under green conditions (low catalyst loadings, solvent-free, room temperature, non-toxic, minimal by-products) are highly desirable in the organic-synthesis field. In this context, we report the use of an aluminum-based catalyst as a highly practical and robust method for hydroborating esters. Lithium diisobutyl-tert-butoxyaluminum hydride (LDBBA), a four-coordinate lithium-ion-based aluminum hydride reagent, significantly reduces esters to their corresponding boronates in the presence of pinacolborane (HBpin) under extremely mild conditions. Furthermore, LDBBA was found to be superior to other examined aluminum hydrides. Gram-scale hydroboration and chemoselective reduction reactions are also reported.