EFFICIENT, SOLVENT-FREE, MICROWAVE-ENHANCED CONDENSATION OF 5,5-DIMETHYL-1, 3-CYCLOHEXANEDIONE WITH ALDEHYDES AND IMINES USING LiBr AS INEXPENSIVE, MILD CATALYST

Efficient, solvent-free, microwave-enhanced condensation of 5,5-dimethyl-1,3-cyclohexanedione with aldehydes using LiBr as catalyst affords xanthenediones. Imines gave only bis-5,5-dimethyl-1,3-cyclohexanediones at high power; a slightly longer period gave xanthenediones. In both types of reactions, the products are obtained in very good to excellent yields. The present protocol is inexpensive and ecofriendly.