Theoretical Analysis of the Mechanism of Cationic Pd(Ⅱ)-catalyzed Fujiwara-Moritani Reaction

A systematic theoretical investigation has been studied on Fujiwara-Moritani reaction between 3-methoxyacetanilide with n-butyl acrylate by means of density functional theory(DFT) calculations when two types of Pd(Ⅱ) catalysts are employed. In [Pd(MeCN)_4](BF_4)_2 catalytic cycle, a 1,4-benzoquinone(BQ)-induced C-H activation of trans-(MeCN)_2Pd(BQ)~(2+) with 3-methoxyacetanilide occurs as the first step to give DC-4_(MeCN), facilitating the insertion of n-butyl acrylate and β-hydride elimination, followed by recycling of catalyst through hydrogen abstraction of monocationic BQ fragment. In Pd(OAc)_(2) catalytic cycle, it is proposed that the most favored reaction pathway should proceed in dicationic mechanism involving a BQ-assisted hydrogen transfer for C-H activation by Pd active catalyst(HOAc)_(2)Pd(BQ)^(2+) to generate DC-4_(HOAc), promoting acrylate insertion and β-hydride elimination, followed by the regeneration of catalyst to give the final product. The calculations indicate that the rate-determining step in [Pd(MeCN)_(4)](BF_4)_(2) catalytic system is the acrylate insertion, while it is the regeneration of catalyst in the Pd(OAc)_(2) catalytic system. In particular, the roles of BQ and ligand effects have also been investigated.