A Dinickel Catalyzed Cyclopropanation without the Formation of a Metal Carbene Intermediate

(NDI)Ni₂ catalysts (NDI=naphthyridine-diimine) promote cyclopropanation reactions of 1,3-dienes using (Me₃ Si)CHN₂ . Mechanistic studies reveal that a metal carbene intermediate is not part of the catalytic cycle. The (NDI)Ni₂ (CHSiMe₃ ) complex was independently synthesized and found to be unreactive toward dienes. Based on DFT models, we propose an alternative mechanism that begins with a Ni₂ -mediated coupling of (Me₃ Si)CHN₂ and the diene. N₂ extrusion followed by radical C-C bond formation generates the cyclopropane product. This model reproduces the experimentally observed regioselectivity and diastereoselectivity of the reaction.