Synthesis of 3-substituted Coumarins: An Efficient Green Approach Using L-proline as Catalyst in Triethanolamine Medium

3-Substituted coumarins were synthesized very efficiently, using Knoevenagel method from salicylaldehydes 1 and active methylene compounds 2 under green conditions. The effect of catalyst and solvent on this condensation was studied. L-proline was found to be the best catalyst and triethanolamine the best reaction medium for this reaction. Keywords: Salicylaldehydes, active methylene compounds, L-proline, triethanolamine, coumarins, Knoevenagel condensation.