A One-Pot Synthesis of Coumarins from Dipotassium O-Methoxybenzylidenemalonates
o-Methoxybenzylidenemalonates 1, which are available from o-methoxybenzaldehydes and diethylmalonate, were hydrolysed to the dipotassium malonates 2.Treatment of the salts 2 with trifluoroacetic acid-trifluoroacetic anhydride gave the title coumarins by a demethylative ring-closure reaction in 60-80percent yield.