Theoretical Study on the Mechanism of Palladium-Catalyzed Synthesis of 5,10-Dihydrophenazasilines via 1,5-Palladium Migration

Previously, we reported a palladium-catalyzed asymmetric synthesis of silicon-stereogenic dibenzosiloles through intramolecular C−H arylation of prochiral 2-(diarylsilyl)aryl triflates. During the course of this study, we found that 3-amino-2-(diarylsilyl)aryl triflates six-membered heterocycle did not provide corresponding dibenzosilole at all under the same condition and instead, six-membered nitrogen-containing heterocycle, 5,10-dihydrophenazasiline, was obtained. This unexpected transformation is supposed to proceed via 1,5-palladium migration and C−N bond-forming reductive elimination. A series of mechanistic investigations were carried out to probe the catalytic cycle of this process, and the 1,5-palladium migration step was suggested to be the enantiodetermining step. However, the origin of the chemo- and stereoselectivity of this process were not theoretically proved. In this work, we theoretically investigate the reaction mechanism by using DFT calculation and elucidate the origin of the selectivity of this reaction.