Silica Sulfuric Acid–Mediated Synthesis of β-Enaminones and β-Enaminoesters Under Microwave Irradiation

Abstract

Silica sulfuric acid, a heterogeneous reagent, has been found to be an efficient catalyst for the synthesis of β-enaminones and β-enaminoesters under microwave irradiation in a microwave reactor within 2 min. The experimental procedure is simple and environment-friendly, and results in excellent yields of the products. Further, the catalyst is recyclable, and the reaction is 60 times faster than the reaction at room temperature.

GRAPHICAL ABSTRACT

Keywords:

• β-Enaminoesters
• β-enaminones
• microwave irradiation
• recyclable catalyst
• silica sulfuric acid

Acknowledgments

We thank Dr. Y. S. Bhat, Professor and Head, Department of Chemistry, Bangalore Institute of Technology, Bengaluru, India, for providing the MILESTONE Microwave Reactor facility, and Mr. Yedunandan, Assistant Professor, V. V. Pura Science College, Bengaluru, India, for the timely help.

Notes

^a All reactions were performed using amine (5 mmol), dimedone/ethylacetoacetate (5 mmol), and silica sulfuric acid (0.26 mmol of H⁺ = 100 mg).

^b Isolated yield; all the compounds are known, and physical properties agree with the reported values. Mass spectral data of all the products match with the reported data.

*Observed melting point [lit. melting point]^ref _.

^aIsolated yield.

^b Present method.

*Reaction conditions: Dimedone (5 mmol), amine (5 mmol), silica sulfuric acid (100 mg), and acetonitrile (2 mL) in a MW reactor at 400 W.