Palladium-Catalyzed Synthesis of Dibenzosilepin Derivatives via 1,n-Palladium Migration Coupled with anti-Carbopalladation of Alkyne.

Catalytic reactions involving 1,n-metal migration represent a powerful method for the synthesis of complex molecules from simple precursors through the activation of C-H bonds. By utilizing this attractive feature, herein we devised a palladium-catalyzed synthesis of new members of 5H-dibenzo[b,f]silepins, a class of underexplored but potentially useful silicon-bridged π-conjugated compounds. The reaction sequence is composed of 1,n-palladium migrations and unusual anti-carbopalladation of alkynes, which was realized by the proper choice of ligand for palladium. A series of deuterium-labeling experiments were conducted toward an understanding of the reaction mechanism to propose plausible catalytic cycles. The newly obtained 5H-dibenzo[b,f]silepins exhibited tunable optical and electronic properties, demonstrating the power and importance of developing a new synthetic method based on 1,n-metal migration processes.