Selective oxidation of sulfides to sulfoxides with tert-BuOOH catalyzed by oxovanadium (IV) asymmetrical tetradentate Schiff base complex

Sulfoxides have a wide range of applications in synthesis of chemically useful and biologically active molecules such as drugs, flavors, germicides, as well as activation ofenzymes [1]. Investigation of environmentally friendly catalytic systems for oxidation of sulfides with high activity and selectivity has become the subject of interest toresearchers. In this regard, the Schiff base transition metal complexes are attractive oxidation catalysts due to their easy synthesis and their chemical and thermal stability.Among different metal Schiff base complexes, special attention has been paid to oxovanadium(IV) Schiff base complexes because of their structural features, catalyticactivity, and biological roles in a variety of biochemical processes [2]. In this work, asymmetrical tetradentate Schiff base ligand was prepared according to published procedure [3] and metallated with VO(acac)2 by refluxing ethanolic solution of Schiff base ligand and VO(acac)2 in 1:1 molar ratio to obtain complex 1. The prepared complex 1 was characterized by FT-IR, UV-vis, 1H NMR spectra and CHN analysis. Then, the synthesized complex 1 successfully used as a new homogeneous catalyst for selective oxidation of sulfides to sulfoxides with tert-BuOOH (TBHP) as oxidant at room temperature (Scheme 1). Good to high yields of products and mild reaction conditions can be mentioned as advantages of this protocol for oxidation of sulfides to sulfoxides