CARO'S ACID SUPPORTED ON SILICA GEL. PART 7: A VERSATILE REAGENT FOR THE AROMATIZATION OF HANTZSCH 1,4-DIHYROPYRIDINES UNDER NON-AQUEOUS CONDITION AND MICROWAVE IRRADIATION

Abstract

Efficient oxidation of 1,4-dihydropyridines with Caro's acid on silica gel is achieved under nonaqueous conditions and in a domestic microwave oven. The reactions under microwave irradiation were shorter in duration and higher in yields than the reactions in conventional method, confirming the potentiality of microwave heating in aromatization of Hantzsch 1,4-dihydropyridines.

Keywords:

• Caro's acid
• dihydropyridines
• oxidation
• silica gel

Financial support by the Mazandaran University research council is gratefully acknowledged.

Notes

^a Reactions were performed in CH₂Cl₂at reflux temperature using 1:3 molar ratio of substrate to oxidation reagent.

^b Isolated yields.

^c Alkylated and dealkylated products.

^a Reactions were conducted under microwave irradiation at 900 w power using 1:3 molar ratio of substrate to caro's acid on silica gel.

^b Yields refer to isolated products.

^c Alkylated and dealkylated products.