Double Suzuki-Miyaura Coupling in the Synthesis of Imidazo[1,2-a]pyridine Derivatives

Significance

Reported is a study on the double Suzuki-Miyaura cross-couplings of 2-(arylsulfonylmethyl)-6,8-dibromo-3-nitroimidazo[1,2-a]pyridine (1) under various conditions. Pd(OAc)₂-catalyzed coupling in water under conventional heating led to requirement for long reaction times and gave poor yields (A). Switching to microwave heating reduced the reaction times to less than an hour and improved the yields markedly (B). The most efficient conditions were found, when solvent and Pd source were changed and the reaction was run under ­microwave heating conditions. The yields were good in view of a double coupling, but the substrate scope was not widely studied.