Introduction of O-sulfonated poly(4-vinylpyrrolidonium) chloride as a polymeric and reusable catalyst for the synthesis of xanthene derivatives

Abstract

O-Sulfonated poly(4-vinylpyrrolidonium) chloride is prepared from the reaction of poly(4-vinylpyrrolidone) [PVP], as a cheap and commercially available reagent, and neat chlorosulfonic acid at room temperature. A variety of techniques including infrared spectra (IR), thermal gravimetric analysis (TGA), scanning electron microscopy (SEM), X-ray diffraction (XRD), pH analysis and Hammett acidity (H_o) were used to characterize this solid acid. This polymeric reagent showed excellent catalytic activity for the synthesis of xanthene derivatives including 1,8-dioxooctahydroxanthenes, 14-aryl-14H-dibenzo[a,j] xanthenes and 12-aryl-8,9,10,12-tetrahydrobenzo[a]xanthen-11-ones under solvent free conditions. The products were formed in excellent yields over short reaction times and the catalyst can be reused several times without any appreciable loss in its activity.