New strategic reactions for organic synthesis:: Catalytic asymmetric C-H activation α to nitrogen as a surrogate for the Mannich reaction

The asymmetric C-H activation reactions of methyl aryldiazoacetates are readily induced by the rhodium prolinate catalyst Rh-2(S-DOSP)(4) (1) or the bridged prolinate catalysts Rh-2(S-biDOSP)(2) (2a) and Rh-2(S-biTISP)(2) (2b). The C-H activation of N-Boc-protected cyclic amines demonstrates that the donor/ acceptor-substituted carbenoids display remarkable chemoselectivity, which allows for highly regioselective, diastereoselective, and enantioselective reactions to be achieved. Furthermore, the reactions can display high levels of double stereodifferentiation and kinetic resolution. The C-H activation is caused by a rhodium carbenoid induced C-H insertion. The potential of this chemistry is demonstrated by a very direct synthesis of threo-methylphenidate.