The Mechanism of the Catalytic Functionalization of Haloalkanes by Carbene Insertion: An Experimental and Theoretical Study

Carbon−halogen (C−X) bonds (X = Cl, Br) can be easily functionalized with ethyl diazoacetate (N 2 CHCO 2 Et) in the presence of silver-based catalysts containing the Tp x Ag core (Tp x = hydrotrispyrazolylborate ligand). Polyhalomethanes are converted into products derived from the formal insertion of the carbene CHCO 2 Et units into the C−X bond. In the case of monohaloalkanes (C 4 −C 6 ), cleavage of the C−X bond is observed, with formation of XCH 2 CO 2 Et and the corresponding olefin. Experimental evidence and theoretical calculations have led to the proposal of a novel mechanism to account for these transformations, in which the metal participates along the pathway in all the reaction steps. Among the experimental data, the first example of a metal-induced, asymmetric functionalization of a C−Cl bond by carbene insertion is included (ee = 14 ± 2%).