The Microwave Promoted Condensation of Aldehydes with Nitromethane

The Knoevenagel condensation reaction of carbonyl-containing compounds with active methylenes is a classic general method for the preparation of valuable synthetic intermediates, while the use of nitroalkanes (Henry reaction) as the methylene component leads to nitroaldol products or nitroalkenes. A multitude of promoters have been developed for these reactions including acids, bases and ammonium salts. Recent reports concerning the ultrasound promoted the Henry reaction^1], led us to consider the application of microwave as another promoter. Repetition of the reaction with the same reagents and application of microwave led to a rapid, clean condensation. This result prompted us to investigate the scope of the method further. The microwave promoted reaction proved to be general (Table 1) for a variety of aromatic aldehydes under these conditions.