Sulfamic acid catalysed synthesis of pyranocoumarins in aqueous media

An efficient, one pot synthesis of pyranocoumarins by the condensation of 4-chloro-3-formylcoumarin with different active methylene compounds via Knoevenagel, Michael and cyclization sequences under homogeneous catalytic conditions using sulfamic acid in aqueous media is reported. The catalyst is found to be active for four cycles.