A number of methods have been proposed for the modification of the Ritter reaction. However, many of these methods involve the use of strongly acidic conditions, stoichiometric amounts of reagents, harsh reaction conditions and extended reaction times. Therefore, the development of mild, efficient, convenient and benign reagents for the Ritter reaction is desirable. In this research, we have developed a clean and environmentally friendly protocol for the synthesis of amides by using different benzylic or tertiary alcohols and different nitriles in the presence of silica-bonded N- propyl sulphamic acid (SBNPSA) as catalyst under solvent-free conditions in high yields.

Silica-bonded 𝑆-sulfonic acid is employed as a recyclable catalyst for the synthesis of naphthoxazinone derivatives from the reaction of 𝛽-naphthol, aromatic aldehydes and urea at 150°C under solvent-free conditions. The heterogeneous catalyst was recycled for five runs after the reaction of 𝛽-naphthol, benzaldehyde and urea without losing its catalytic activity.