Origin of Regioselectivity Inversion Tuned by Substrate Electronic Properties in Co(III)-Catalyzed Annulation of N-Chlorobenzamide with Alkenes.

The mechanisms of Co(III)-catalyzed annulations of N-chlorobenzamide with olefins bearing different electronic properties were computationally studied and the origins of regioselectivity reversal were investigated by using energy decomposition analysis (EDA). The alkene migratory insertion step determines the regiochemistry of these reactions. EDA results indicate that the 2,1-insertion with styrene is favored because there is a weaker Pauli repulsion between the cobaltacycle Co-C σ orbital and the olefin π orbital. Conversely, the 1,2-insertion with vinyltrimethylsilane is more favorable than the 2,1-insertion. This is mostly because the increased π electron density can effectively differentiate the stabilizing electronic interactions.