Iridium-catalyzed enantioselective allylic alkylation with functionalized organozinc bromides

Iridium-catalyzed enantioselective allylic alkylation of branched racemic carbonates with functionalized alkylzinc bromide reagents is described. Enabled by a chiral Ir/(P,olefin) complex, the method described allows allylic substitution with various primary and secondary alkyl nucleophiles with excellent regio- and enantioselectivities. The developed reaction was showcased in a concise, asymmetric synthesis of (-)-preclamol. An Ir/(P,olefin) complex catalyzes the title reaction and the method provides a variety of allylated products with excellent regio- and stereoselectivities. The utility of the coupling is demonstrated in a catalytic enantioselective synthesis of a preclinical drug (-)-preclamol. Boc=tert-butyloxycarbonyl, cod=1,5-cyclooctadiene.