The rhodium(II)-catalyzed reaction of N-bis(trimethylsilylmethyl)diazoamides: steric, electronic and conformational effects

The N-bis(trimethysilyl)methyl (N-BTMSM) group is effective for conformational control about the amide NC(O) bond in tertiary diazoamides; metallocarbenoid C–H insertion reaction occurs only at the other N-‘alkyl’ unit. In Cα-unbranched diazoamides, the inherent electronic effects of the N-‘alkyl’ group influence the regioselectivity of the reaction. The N-BTMSM group also influences the conformational preference about the amide N–Cα bond in Cα-branched systems which, in turn, affects the regioselectivity of the reaction; substituent electronic effects are subtle and play subordinate roles. A transition state model to explain the results is proposed.