Facile synthesis of 4-acetyl-coumarins, -thiocoumarin and -quinolin-2(1H)-one via very high α-regioselective Heck coupling on tosylates

An efficient synthesis of a series of methyl ketones at the C4 position of coumarins, coumarin-containing heterocycles and analogous scaffolds is reported via very high α-regioselective Heck coupling using tosylates and in very high yields. Although α-regioselectivity in Heck coupling can be obtained with triflates as substrates, tosylates are less toxic, less expensive and, importantly, more stable.