Intermolecular C–H functionalization versus cyclopropanation of electron rich 1,1-disubstituted and trisubstituted alkenes

Rhodium(II)-catalyzed reactions of aryldiazoacetates with electron rich 1,1-disubstituted and trisubstituted alkenes were systematically studied. The regio-, diastereo- and enantioselectivity of the chemistry was profoundly influenced by the nature of the substrates and the catalyst. Conditions were developed for either selective cyclopropanation or C–H insertion. Both reactions can be achieved with high diastereo- and enantioselectivity (for C–H insertion: >90% de, up to 96% ee, for cyclopropanation: >94% de, up to 95% ee). For the 1,1-disubstituted vinyl ethers, cyclopropanation occurs with variable diastereoselectivity but in optimized systems the cyclopropane is formed in >94% de and up to 98% ee.