The influence of an acid additive on linear and branch selectivity in the C–H alkylation of N-pyridinecarbonyl-protected 2-methylbenzylamine with 1-heptene catalyzed by Rh2(OAc)4: a theoretical investigation

Abstract

The mechanism of selective C–H alkylation of benzylamine has been meticulously investigated employing density functional theory (DFT) calculations. The mechanistic investigations in this study indicate that the twisted paddlewheel-shaped intermediate is pivotal in the catalytic process. Furthermore, the distinctive double gear architecture of the dirhodium complex significantly contributes to its catalytic efficiency. With 2,6-difluorobenzoic acid as the additive, the hydrogen bonding interactions between C–H⋯F and C–H⋯O enhance the stability of the transition state associated with the linear product relative to that of the branched product during the selectivity-determining step, consequently favoring the formation of the linear product. When phenylpropiolic acid is employed, the branched product becomes preferred due to the stronger coulombic attraction found in the transition state of the branch selectivity-determining step compared to that of the linear selectivity-determining transition state.