Non-C2 symmetric chiral ligand dictating allyl-allyl coupling.

Abstract

Enantioselective synthesis of chiral compounds is of high interest due to their importance in organic chemistry, medicinal chemistry, life science, and materials science. Catalytic construction of chiral centers via the enantioselective carbon-carbon coupling is one of the most efficient approaches. Chiral 1,5-alkadienes are prevalent in natural and bioactive compounds. Thus, allyl-allyl coupling towards to the synthesis of chiral 1,5-alkadienes is of high interest. However, in addition to the issue of enantioselectivity, the extra challenge is the issue of regio-selectivity referring to the branched and linear products caused by the steric and electronic effect of 1,3-terminals. Herein, such challenge is addressed by a synergistic copper/palladium catalysis strategy: A three-component allylboration reaction of allenes with bis(pinacolato)diboron and allylic phosphates is developed to afford a series of optically active 1,5-alkadienes with either tertiary or quaternary carbon stereocenters. Their synthetic potentials are demonstrated, including the synthesis of (-)-protrifenbute and its derivatives.