Silica vanadic acid [SiO2–VO(OH)2] as an efficient heterogeneous catalyst for the synthesis of 1,2-dihydro-1-aryl-3H-naphth[1,2-e][1,3]oxazin-3-one and 2,4,6-triarylpyridine derivatives via anomeric based oxidation

Abstract

Silica-bonded vanadic acid [SiO₂–VO(OH)₂] (SVA) efficiently catalyzed the synthesis of 1,2-dihydro-1-aryl-3H-naphth[1,2-e][1,3]oxazin-3-ones via reacting aromatic aldehydes and β-naphthol and urea under solvent-free condition. Additionally, 2,4,6-triarylpyridine derivatives were prepared through the condensation of ammonium acetate, aromatic aldehyde and various acetophenone in the presence of a catalytic amount of [SiO₂–VO(OH)₂] (SVA) under a same condition. A new anomeric based oxidation was proposed for the final step of the 2,4,6-triarylpyridine derivatives synthesis which was supported by theoretical studies. So the described new mechanistic approach can open up a new and promising insight in the course of rational design, synthesis and applications of novel hydride releasing compounds. The significant features of the present procedure are short reaction time, high yields, easy work-up, and recyclability of the SVA catalyst.