Efficient, Solvent-Free, Microwave-Enhanced Condensation of 5,5-Dimethyl-1,3-cyclohexanedione with Aldehydes and Imines Using LiBr as Inexpensive, Mild Catalyst

Abstract

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.

Keywords:

• Aldehydes
• 3-cyclohexanedione
• 5-5-dimethyl-1
• imines
• LiBr
• solvent-free
• xanthenedions

ACKNOWLEDGMENTS

The authors are thankful to the Council of Scientific and Industrial Research, New Delhi, India, for financial assistance and to the Indian National Science Academy for additional financial support for this research project.

Notes

^a The products were characterized by comparison of their melting points and spectral (IR, ¹H NMR) data with those of authentic samples.

A, A′, and A″ are isolated yields (yields were nearly all the same in all cases) obtained from simple grinding, heating on a water bath, and MWI.

^a The products were characterized by comparison of their melting points and spectral (IR, ¹H NMR) data with those of authentic samples.