
Poly(4-vinylpyridinium)hydrogen sulfate: A novel and efficient catalyst for the synthesis of 13-aryl-indeno[1,2-b]naphtha[1,2-e]pyran-12(13H)-ones under solvent-free conditions
Keywords: Poly(4-vinylpyridinium)hydrogen sulfate; Indenonaphthopyrans; 2H-indene-1,3-dione; β-Naphtho