Microwave-Assisted, Rapid, Solvent-Free Aza-Michael Reaction by Perchloric Acid Impregnated on Silica Gel

Abstract

Highly efficient solvent-free aza-Michael additions of a variety of amines to α,β-unsaturated carbonyl compounds under microwave-irradiation conditions catalyzed by perchloric acid impregnated on silica gel (HClO₄/SiO₂) is reported. The reactions are completed within 2–7 min in a microwave oven to produce the corresponding adducts in excellent yields, and the catalyst can be recovered and reused.

Keywords:

• Aza-Michael reaction
• HClO₄/SiO₂
• hydroamination
• microwave irradiation
• reusable catalyst
• solvent-free

ACKNOWLEDGMENTS

Financial assistance from Indian Institute of Chemical Technology–Aisin Cosmos Collaborative Research Project is acknowledged. We thank P. S. Sai Prasad for providing the microwave laboratory station facility.

Notes

^a Typical reaction procedure is given.

^b Isolated yield based on the amine after purification.

^c Isolated yield after fourth cycle.

^d The amine (5.0 mmol) is used.

^e Yield of the bis-adduct with 2.4 equiv of acceptor.