Oxo/imido heterometathesis of N-sulfinylamines and carbonyl compounds catalyzed by silica-supported vanadium oxochloride

A series of silica-supported vanadium oxo complexes has been prepared via water-free grafting VOCl3 onto the silica surface. The obtained materials have been characterized with Raman, diffuse reflectance FTIR (DRIFT) and UV–vis, 51V solid-state NMR and X-ray photoelectron spectroscopies, elemental analysis and N2 physisorption. The samples with a low vanadium loading (1–5%) have been found to be comprised primarily of the isolated tetrahedral d0 units (triple bond; length of mdashSiO)V(double bond; length as m-dashO)Cl2, whereas the materials with a higher vanadium content are contaminated with a significant amount of d1 vanadium species. The silica-supported vanadium complexes act as heterogeneous catalysts for oxo/imido heterometathesis between N-sulfinylamines and carbonyl compounds affording imines and SO2. Grafting VOCl3 onto silica leads to a dramatic enhancement of its catalytic activity. A novel water-free express method for preparation of imines of wide range of aldehydes and some ketones has been developed. Noteworthy, this is the first example of transition metal mediated heterometathetical imidation of ketones.