Intermolecular Hydroamination of Vinylarenes by Iminoanilide Alkaline‐Earth Catalysts: A Computational Scrutiny of Mechanistic Pathways

Abstract A thorough computational exploration of the mechanistic intricacies of the intermolecular hydroamination (HA) of vinylarenes by a recently reported class of kinetically stabilised iminoanilide [{N^N}Ae{N(SiMe 3 ) 2 } ⋅ (THF) n ] alkaline‐earth amido compounds (Ae=Ca, Sr, Ba) is presented. Two distinct mechanistic pathways for catalytic HA mediated by alkaline‐earth and rare‐earth compounds have emerged over the years that account equally well for the specific features of the process. On one hand, a concerted proton‐assisted pathway to deliver the amine product in a single step can be invoked and, on the other, a stepwise σ‐insertive pathway that comprises a rapid, reversible migratory olefin insertion step linked to a less facile, irreversible AeC alkyl bond aminolysis. The results of the study presented herein, which employed a heavily benchmarked and reliable DFT methodology, supports a stepwise σ‐insertive pathway that involves fast and reversible migratory CC bond insertion into the polar AeN pyrrolido σ bond. This proceeds with strict 2,1 regioselectivity via a highly polarised four‐centre transition state (TS) structure, linked to irreversible intramolecular AeC bond aminolysis of the alkaline‐earth alkyl intermediate as the energetically favourable mechanism. Turnover‐limiting aminolysis is consistent with the significant KIE measured; the DFT‐derived effective barrier matches the Eyring parameter empirically determined for the best‐performing {N^N}Ba(NR 2 ) catalyst gratifyingly well. It also predicts the observed trend in reactivity (Ca

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