Sulfated titania (TiO2-SO42−) as an efficient and reusable solid acid catalyst for the multi-component synthesis of highly functionalized piperidines

Abstract

An efficient and one-pot procedures have been developed for the synthesis of highly functionalized piperidine derivatives via pseudo five-component reactions in the presence of sulfated titania (TiO2-SO42−) as a heterogeneous solid acid catalyst was reported for the first time. The pseudo five-component reactions of aromatic aldehydes, aromatic amines, and β-keto esters catalysed by sulfated titania (TiO2-SO42−) in methanol at 70°C provides highly functionalized piperidine derivatives in good to excellent yields. The structure as well as the relative stereochemistry of these functionalized piperidines was confirmed by melting points, IR, 1H, and 13C NMR spectral data and single crystal X-Ray analysis. This sulfated titania (TiO2-SO42−) gives an good to excellent yield with short reaction time and is inexpensive, easily recyclable catalytic material for this reaction. Higher catalytic activity of sulfated titania (TiO2-SO42−) is due to its increased Bronsted acidity.