Iridium-Catalyzed Intermolecular Asymmetric Hydroheteroarylation of Bicycloalkenes

Catalytic hydroarylation of alkenes is a desirable process because it can occur under neutral conditions with regioselectivity complementary to that of acid-catalyzed reactions and stereoselectivity derived from the catalyst. We report an intermolecular asymmetric addition of the C-H bonds of indoles, thiophenes, pyrroles, and furans to bicycloalkenes in high yield with high enantiomeric excess. These heteroarene alkylations occur ortho to the heteroatom. This selectivity is observed even with unprotected indoles, which typically undergo alkylation at the C3 position. Initial mechanistic studies revealed that oxidative addition of a heteroarene C-H bond to a neutral Ir(I) species occurs within minutes at room temperature and occurs in the catalytic cycle prior to the turnover-limiting step. Products from syn addition of the C-H bond across the olefin were observed.