Uncatalysed reactions in water: Part 2. Preparation of 3-carboxycoumarins

A simple, efficient and environmentally friendly procedure has been developed for the reaction of Meldrum's acid with salicylaldehydes. 3-Carboxycoumarins 5 were synthesised in high yields (78-96%) and excellent selectivities (95-98%) by carrying out the reaction in water at reflux for 10 h, avoiding the addition of any catalyst.