Highly selective intramolecular carbene insertion into primary C-H bond of α-diazoacetamides mediated by a (p-cymene)ruthenium(II) carboxylate complex.

Complex [(p-cymene)Ru(η(1)-O(2)CCF(3))(2)(OH(2))] mediated transformation of α-diazoacetamides ArCH(2)N(C(CH(3))(3))C(O)CHN(2) to result in carbene insertion into the primary C-H bond exclusively, with the γ-lactam products being isolated in up to 98% yield. This unexpected reaction is striking in view of the presence of usually more reactive sites such as secondary C-H bonds in the substrates. DFT calculations based on proposed Ru-carbene species provide insight into this unique selectivity.