Effect of Microwave Irradiation on Reaction of Arylaldehyde Derivatives with Some Active Methylene Compounds in Aqueous Media

The effect of microwave irradiation on the condensation reactions of arylaldehydes 1 and active methylene compounds 2 in aqueous media was studied and compared with “classical” conditions. The results show that the condensation was carried out only under microwave irradiation in the presence of ammonium chloride as a catalyst, followed by dehydration, to afford (E)‐olefins 3. The protocol was used to synthesize coumarins by a condensation reaction of salicylaldehyde or its derivatives with various derivatives of ethylacetate 5 (e.g., R3CH2CO2Et; R3: CO2Et, CO2Me, COMe, CN) in high yields. These investigations will contribute to the development of environmentally friendly and inexpensive processes in organic synthesis.