An efficient synthesis of 4-substituted coumarin derivatives via a palladium-catalyzed Suzuki cross-coupling reaction

Abstract An efficient Pd-catalyzed Suzuki cross-coupling reaction of sterically crowded 4-chlorocoumarin derivatives with air- and moisture-stable potassium organotrifluoroborates is developed. This methodology has been used to generate a series of novel alkyl, aryl, and vinyl substituted coumarin derivatives in good to excellent yields. The twisted conformation of the vinyl groups in the X-ray crystal structures of (2-oxo-4-vinyl-2 H -chromen-3-yl)methyl acetate ( 2 ) and (2-oxo-4-vinyl-2 H -chromen-3-yl)methyl 2,2,2-trichloroacetimidate ( 3 ), along with the atropisomerism of 3-(hydroxymethyl)-4-(2-methoxyphenyl)-2 H -chromen-2-one ( 1d ), are evidence of the steric crowding in these adducts.