P,O-Ferrocenes in Suzuki−Miyaura C,C Couplings

Abstract

It is generally accepted that efficient Suzuki−Miyaura catalysts contain sterically demanding and strongly Lewis-basic phosphines. Herein we report on the use of chiral P,O-ferrocenes in the synthesis of sterically hindered biaryls by the palladium-catalyzed Suzuki−Miyaura coupling. It is apparent that a decrease of the phosphine Tolman cone angle results in a higher catalytic productivity, which is contradictory to what is known as a good Suzuki−Miyaura catalyst. In addition, the P,O-ferrocenes were successfully applied for couplings of nonactivated aryl bromides with aromatic boronic acids at catalyst loadings as low as 1 ppm achieving quite high turnover numbers (TONs) of up to 750,000.