H4SiW12O40: An efficient catalyst for the synthesis of new spiro- [dibenzo [a,i] xanthene- 14,3′-ind

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 H4SiW12O4o.This protocol provides a simple one-step procedure with the advantages of easy work-up,mild reaction conditions and environmentally benign.