Abstract
Acetone and various benzaldehyde substituted with methyl, chioro, methoxy and hydroxyl groups were reacted with amine-silica gel (230-400 mesh) under ultrasonic irradiation(Sus-4005C, 50W, 40kHz) for 2h to give the corresponding aldol condensation products: compound 3 and 4. From 4-methylbenzaldehyde with acetone gave 4-(4-methylphenyl)-4-hydroxy-2-butanone and 4-(4-methylphenyl)-3-buten-2-one, respectively. In the case of ultrasonic irradiation, the compound 4 was mainly produced. On the other hand, compound 3 was predominantly produced under no ultrasonic irradiation. Phenolic aldehyde and acetone were reacted with amine-SiO_2 under ultrasonic irradiation to give the corresponding aldol condensation products without any byproduct which was produced by the reaction of phenolic hydroxy group. This method is a good way to obtain the mild and selective aldol condensation products from the starting materials very susceptible to strong base.
