Poly(4-vinylpyridinium) hydrogen sulfate: an efficient catalyst for the synthesis of xanthene derivatives under solvent-free conditions

A simple and convenient procedure for the synthesis of xanthene derivatives is described through a one-pot condensation of 2-naphthol {2-hydroxynaphthalene-1,4-dione or the mixture of 2-naphthol and 2-hydroxynaphthalene-1,4-dione} with aryl aldehydes in the presence of poly(4-vinylpyridinium)hydrogen sulfate as an efficient, cheap, easily synthesised and eco-friendly catalyst under solvent-free conditions. Further, the catalyst can be reused and recovered several times without any variations in the yield of the product.