H4SiW12O40: An efficient catalyst for the synthesis of new spiro-[dibenzo[a,i]xanthene-14,3′-indoline]-2′,8,13-triones

Novel spiro[dibenzo[a,i]xanthene-14,3′-indoline]-2′,8,13-triones were prepared by the three-component reaction of β-naphthol, isatins, and 2-hydroxy-1,4-naphoquinone in the presence of a catalytic amount of H4SiW12O40. This protocol provides a simple one-step procedure with the advantages of easy work-up, mild reaction conditions and environmentally benign.