Synthesis of Pyridine-Fused Siloles by Palladium-Catalyzed Intramolecular Bis-Silylation

Silole derivatives are attracting significant attention as new functional materials with excellent electronic and photophysical properties. Thus, the development of synthesis methods to afford such derivatives is highly desirable. Herein, the synthesis of pyridine-fused siloles under the conditions of the Sonogashira coupling reaction is described. The reactions of 2-bromo-3-(pentamethyldisilanyl)pyridine (1) with ethynylbenzene derivatives in the presence of PdCl₂(PPh₃)₂-CuI as a catalyst afforded the corresponding pyridine-fused siloles (2a-2c) through intramolecular trans-bis-silylation. DFT calculations were also performed to understand the reaction mechanism. This paper is the first to report on the successful use of palladium catalysts in the trans-bis-silylation of alkynes with disilanes.