Cycloaddition of homophthalic anhydrides with aldehydes and ketones: a route to 3,4-dihydroisocoumarin-4-carboxylic acid derivatives

Homophthalic anhydride reacts with benzaldehyde, in the presence of boron t rifluoride - diethyl ether complex to give the cycloadduct 3-phenyl-3,4-dih ydroisocoumarin-4-carboxylic acid in good to excellent yield. Under these c onditions, we did not observe the formation of Perkin-type products. The re action can be extended to a wide variety of aldehydes and to some ketones i n synthetically useful yields. Amides can be obtained in good yields after activation of the carboxylic function with DCC at O degrees C. (C) 1999 Els evier Science Ltd. All rights reserved.