Mechanisms of Cu/DMAP Cocatalyzed and DMAP-Catalyzed C-N Decarboxylative Cross-Coupling Reactions

Abstract

A general practical type of Cu/DMAP cocatalyzed and DMAP-catalyzed C-N decarboxylative cross-coupling (DCC) reactions of carboxylic acids (or carboxylates) and azdioformates, which can construct both C(sp2)-N and C(sp3)-N bonds, was thoroughly investigated by density functional theory calculations. The Curtius Rearrangements, i.e. extrusions of N2, were exposed to be the rate-limiting steps for both Cu/MDAP cocatalyzed and DMAP-catalyzed C-N DCC reactions. DMAP can facilitate the N3- transfer from the initial azidoformate species to the ensuing generated acyl azide intermediates. Then, the acyl azide intermediates undergo the Curtius Rearrangements, overcoming a relatively low barrier. If DMAP were absent, the Curtius Rearrangements would have to occur on the initial azidoformate species with barriers over 40.0 kcal/mol, which is not feasible at room temperature. Cu catalysts can further slightly facilitate the C-N DCC reactions.