HClO4•SiO2-Catalyzed Mechanochemical Protocol: An Effective, Economical and Eco-friendly Preparation of N-(tert-butylsulfinyl)imines

The imines of Ellman's tert-butylsulfinamides have become one of the elementary substrates for the construction of chiral precursors and complex organic molecules. This article reports a mechanochemical access to imines of chiral tert-butylsulfinamides with a variety of aldehydes using solid acid catalyst, perchloric acid-silica (HClO4 center dot SiO2) at innocuous reaction environs. The conversion can be carried out at ambient temperature under solvent and metal-free conditions by (hand) grinding the contents in a mortar at open-air. The current protocol is highly economical, allows large-scale preparation, offers a very good to nearly quantitative yields of imines in short reaction times with no product racemization and doesn't necessitate the moisture-free conditions.