Efficient Oxidation of Hantzsch 1,4-Dihydropyridines with Tetrabutylammonium Peroxomonosulfate Catalyzed by Manganese(III) Schiff Base Complexes: The Effect of Schiff Base Complex on the Product Selectivity

Abstract

Efficient and rapid oxidation of Hantzsch 1,4-dihydropyridine with tetrabutylammonium peroxomonosulfate (TBAO) is reported. The Mn(salophen)/monopersulfate catalytic system efficiently converts 1,4-dihydropyridines (DHPs) to their corresponding pyridine derivatives under mechanical stirring and microwave irradiation in CH₂Cl₂. The ability of various Schiff base complexes to oxidize DHPs was also investigated. The results showed that in the presence of manganese Schiff complex, no by-product was obtained.

Keywords:

• Biomimetic oxidation
• 1,4-dihydropyridine
• manganese(III) Schiff base
• tetrabutylammonium peroxomonosulfate

ACKNOWLEDGMENT

The partial support of this work by Yasouj University Council of Research is acknowledged.

Notes

^a Reaction conditions: 4-phenyl derivative of 1,4-dihydropyridines (1 mmol), TBAO (2 mmol), catalyst (0.067 mmol), and CH₂Cl₂ (10 mL).

^b Isolated yield.

^a All products were identified by comparison with authentic samples (IR, ¹H NMR, mp). Reaction conditions are TBAO (2 mmol), DHP (1 mmol), and Mn–salophen (0.067 mmol) in CH₂Cl₂ (10 mL).

^b Isolated yields.

^c The yields are in the absence of catalyst.

^d The product is a dealkylated pyridine derivative.