Metal-Carbenoid-Mediated Selective Transformation: Experimental and DFT Studies of Ag, Pd, and Rh with Enaminones and Diazoesters

Transition-metal-catalyzed transfer of a carbene group via in situ generated carbenoid intermediates from α-diazocarbonyls is a powerful method for initiating diverse cascade sequences that rapidly lead to the generation of structural complexity. Despite significant advancements in carbenoid-enabled catalytic pathways, such as insertions and cyclopropane formation, there has been limited exploration of the selective control of catalytic processes involving carbenoid chemistry. In this study, we reported a metal-carbenoid-mediated cascade transformation approach that allows for selective control by employing different transition metals, including silver, palladium, and rhodium, assisted by a comprehensive density functional theory (DFT) mechanism investigation. Through detailed mechanistic studies, we demonstrate that silver-carbenoids and rhodium-carbenoids yield distinct tandem cyclization products, while palladium-carbenoids afford quaternary α-imine compounds as the final product through direct proton transfer from the same intermediate. Furthermore, the origin of the catalyst-dependent selectivity is elucidated through DFT calculations.