Organocatalytic Asymmetric Electrophilic Amination of Allylic Boronates

The asymmetric addition of allylic boronates to electrophiles is a powerful method for preparing chiral molecules bearing synthetically valuable allylic moieties. While effective catalytic methods exist, they have so far been limited to the enantioselective allyl- and crotyl-boration of carbonyl compounds and imines, thereby forming C-C bonds. Here, we present a strategy that expands the scope of this catalytic asymmetric platform to include the stereoselective formation of C-N bonds. We have identified an inexpensive and readily available chiral diol that catalyzes the addition of allylic boronates to azodicarboxylates, affording chiral allylic hydrazides with high stereocontrol. This electrophilic amination chemistry shows a broad substrate scope and requires mild conditions, proceeding at ambient temperature. Mechanistic studies reveal that the chiral diol catalyst facilitates the formation of a chiral allylic boronate through the reversible exchange of the boron's achiral alkoxy ligand. By coordination with the electrophilic azodicarboxylate, the substrates mutually activate each other, allowing for the stereoselective transfer of the allyl group.