Preparation of pyridine-2-boronic esters, thiazole-4-boronic esters, and pyrazine-2-boronic esters

ORGN 86

George Y. Li, George.Y.li@combiphos.com, Maoying Song, Ao Yang, Shilong Zheng, and Xiaomei Qi. CombiPhos Catalysts, Inc, P.O. Box 220, Princeton, NJ 08542
Pyridine-2-boronic esters, thiazole-4-boronic esters, pyrazine-2-boronic esters are important intermediates for a variety of Suzuki coupling reactions. However, “unstable” nature limits their preparation and applications. We successfully found air-stable metal-phosphinous acid compounds to be remarkably active and efficient catalysts for a variety of C-B cross-coupling reactions of aryl halides with bis(pinacolato)diboron. Herein, we report a mixture of air-stable "combinatorial" palladium complexes served as efficient catalyst precursors for synthesis of “historically unstable” pyridine-2-boronic esters, thiazole-4-boronic esters, and pyrazine-2-boronic esters through catalytic C-B coupling reactions.