The catalytic potential of wolfium bonds, a σ–hole interaction involving Group 6 elements, remains largely unexplored. Herein, we present a systematic theoretical investigation into the mechanism of wolfium bond donors (WnF4O, Wn = Cr, Mo, W) as catalysts for the aza-Diels–Alder reaction between imine and 1,3-butadiene. Computations performed at the ωB97XD/aug-cc-pVTZ level reveal that these catalysts function via a prestabilization mechanism, forming strong wolfium bonds with the imine reactant. This interaction not only significantly lowers the apparent activation barrier but also reprograms the reaction pathway toward an asynchronous, charge-separated transition state. Catalytic efficiency follows the order Cr < Mo < W, which originates from the enhanced electrostatic and polarization components of the wolfium bond with increasing metal electronegativity and polarizability. Energy decomposition and AIM analyses confirm the electrostatic-dominated, partially covalent nature of these interactions. Crucially, solvent effect studies identify WF4O as an effective modulator of the reaction pathway in both nonpolar and polar media. Compared to conventional hydrogen and halogen bonds, wolfium bonds exhibit a more pronounced ability to regulate the reaction mechanism, offering a new perspective on the role of noncovalent interactions in pericyclic reactions.
Liu et al. (Thu,) studied this question.