Ultrasound-promoted Cannizzaro reaction under phase-transfer conditions

Ultrasound accelerates the Cannizzaro reaction of p-chlorobenzaldehyde under phase-transfer conditions. Of the three phase-transfer catalysts which were tested [benzyltriethylammonium chloride (TEBA), Aliquat and 18-crown-6] TEBA was found to be the most effective. Ferrocenecarbaldehyde and p-dimethylaminobenzaldehyde gave, under similar conditions (TEBA as the catalyst), 1,5-diaryl-1,4-pentadien-3-ones as the main product. The possible route leading to these compounds is suggested and discussed.