N-Phthalimide as a Site-Protecting and Stereodirecting Group in Rhodium-Catalyzed C–H Functionalization with Donor/Acceptor Carbenes

The rhodium-catalyzed enantioselective C–H functionalization of unactivated C–H bonds by means of donor/acceptor carbene-induced C–H insertion was extended to substrates containing nitrogen functionality. The rhodium-stabilized donor/acceptor carbenes were generated by rhodium-catalyzed decomposition of aryldiazoacetates. The phthalimido group was the optimum nitrogen protecting group. C–H functionalization at the most sterically accessible methylene site was achieved using Rh2(S-2-Cl-5-BrTPCP)4 as catalyst, whereas Rh2(S-TPPTTL)4 was the most effective catalyst for C–H functionalization at tertiary C–H bonds and for the desymmetrization of N-phthalimidocyclohexane.