Clean synthesis of novel spiro[indene-2,2'-[1,3,5]-oxathiazine]-1,3-diones in water

An efficient and convenient method for the synthesis of novel spiro[indene-2,2'-[1,3,5]oxathiazine]-1,3-diones by the one-pot, three component condensation of tetramethyl guanidine, ninhydrin, and isothiocyanates in water was reported. Easy purification, green reaction conditions, easy performance and good yields are some advantages of this procedure.