Mechanism and Origins of Diastereo- and Regioselectivities of Palladium-Catalyzed Remote Diborylative Cyclization of Dienes via Chain-Walking Strategy

Density functional theory calculations have been performed to investigate the palladium-catalyzed remote diborylative cyclization of dienes. The computations reveal that the reaction proceeds through a rarely explored Pd(II)/Pd(IV) catalytic cycle, and the formal sigma-bond metathesis between the alkylpalladium intermediate and B(2)pin(2) occurs via the pathway of the B-B oxidative addition/C-B reductive elimination involving the high-valent Pd(IV) species. The diastereoselectivity is determined by the migratory insertion into the Pd-C bond, which is mainly due to the combination of the torsional strain effect, steric repulsion and C-H-O hydrogen-bonding interaction. The steric hindrance around the reacting carbon group in the C-B reductive elimination turns out to be a key factor to provide the driving force of the chain walking of the Pd center to the terminal primary carbon position, enabling the experimentally observed remote regioselectivity.

Automated summary

Density functional theory calculations were used to study the palladium-catalyzed remote diborylative cyclization of dienes. The computations revealed a Pd(II)/Pd(IV) catalytic cycle and the involvement of a high-valent Pd(IV) species in the sigma-bond metathesis between the alkylpalladium intermediate and B(2)pin(2) via B-B oxidative addition/C-B reductive elimination. The diastereoselectivity was found to be determined by the migratory insertion into the Pd-C bond, influenced by torsional strain, steric repulsion, and C-H-O hydrogen bonding.