Simple and Efficient One-Pot Preparation of 3-Substituted Coumarins in Water

Abstract

3-Cyanocoumarin and seven derivatives 14-Me; 6-NO2: 7-OH, 7-OMe; 8-OH: 5,7-OMe; 6.7-(-CH=CH-)-,I and eight coumarins substituted at C-3 (C02Et; NO,; Ph; pN0,-C,H,; Ph-SO,; 2-pyridyl; 2-thienyl; 2-benzothiazolyl) were prepared, on multigram scale by a one-pot procedure in water alone, by the Knoevenagel reaction of o-hydroxyaryl aldehydes and o-hydroxyacetophenone with acetonitriles.The yields are high and the procedure does not require organic solvents.The reactions carried out in heterogeneous aqueous phasc.sometimes in the presence of a surfaclant, always have higher yields than the same reactions executed in homogeneous ethanolic medium.