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DFT calculations were performed to elucidate the origins of catalyst-controlled product selectivity in the decarboxylative transformations of isoxazolones.

This paper presents a density functional theory study concerning the mechanisms and origin of regioselectivity associated with a Mn-catalyzed denitrogenative annulation involving benzonitrile as the substrate and a click reaction...

Au(I)-catalyzed coupling of benzisoxazoles and ynamides was recently reported to synthesize challenging indoloquinoline core structures. In this report, we employed DFT methods to elucidate the mechanistic details of this reaction. The results reveal that the catalytic cycle involves initial coupling of ynamide with benzisoxazole, simultaneous ring opening of the isoxazole unit and attack of the dimethoxybenzene (DMOB) unit to gold carbenoid, proton transfer from the DMOB group to hydroxyl group, thioether migration, ring closure, and proton transfer. The experimentally observed ligand-controlled product selectivity is reproduced well by the calculations. The product selectivity-determining step is the ring opening of the isoxazole unit. The flexible P(t-Bu) 2 (o-biphenyl) ligand facilitates the approach of the DMOB group to gold carbenoid, which brings about significant CÀ H/π interactions in the transition state for ring opening, and thus leads to the indoloquinoline product. The rigid 1,3-bis(diisopropylphenyl)imidazol-2-ylidene ligand prefers keeping the DMOB group away from the gold carbenoid, which can cause strong orbital interaction in the transition state for ring opening, and thus results in indole product.