synthesis and characterization of a novel nanosilica supported bipyridinium chloride nanocomposite and its application as a basic catalyst in the one-pot preparation of tetrahydrobenzo[b]pyran, dihydropyrano[3,2-c]chromene and dihydropyrano[4,3-b]pyran derivatives

a novel rice-husk-silica supported n-propyl bipyridinium chloride (rhprbpcl) has been prepared. due to the basicity of rhprbpcl, it was decided to evaluate its catalytic activity in the one-pot preparation of tetrahydrobenzo[b]pyran, dihydropyrano[3,2-c]chromene and dihydropyrano[4,3-b]pyran derivatives. the catalyst was characterized by ft-ir, sem and tga analyses. this methodology offers several advantages including easy work-up procedure, high yields of the products, short reaction times, recyclable catalyst and green reaction medium.