Reactivity of (poly)fluorobenzamides in palladium-catalysed direct arylations

Abstract

The influence of fluoro-substituents on secondary and tertiary benzamides on the regioselectivity of palladium-catalysed direct arylations was studied. With most (poly)fluoro-substituted tertiary benzamides, the arylations proceed very regioselectively at ortho-positions of the fluoro substituents using 1 mol% of air-stable palladium catalysts and PivOK/DMA as the reaction conditions. With the 3,5-difluoro-substituted secondary benzamides, quite regioselective arylations at C4-positions were observed. For these reactions, a variety of substituents on the aryl bromide, such as ester, propionyl, acetyl, formyl, nitro, nitrile, trifluoromethyl, chloro, fluoro or methyl, was tolerated. These results reveal that under our reaction conditions, fluoro substituents act as better directing groups than amides in the palladium-catalysed direct arylations.