Regioselective access to substituted oxindoles via rhodium-catalyzed carbene C-H insertion

Rhodium-catalyzed decomposition of diazoamides followed by insertion of the resulting carbenes into an aromatic C-H bond gives access to substituted oxindoles. The reaction takes place with aromatic rings substituted by either electron-donating or -withdrawing groups at ortho, meta or para positions and the regioselectivity can be controlled by a substitution α to the diazo functionality. In the presence of an ester, the reaction leads to the formation of 2-silyloxyindole-3-carboxylates in 40-85% yields and regioselectivities up to 80% are observed in the case of meta-substituted substrates. This selectivity mainly relies on steric factors and use of a more bulky N,N-diethylamide then affords 2-silyloxyindole-3-carboxamides in 42-91% yields with complete regioselectivity.