Structurally diverse spiroheterocycles with fused heterosystems; spiro[benzothiazolo[2,3-b] chromeno[3,4-e]pyrimidine-7,3′-indoline]-2′,6-diones, spiro[benzothiazolo[2,3-b]pyrimido[5,4-e]pyrimidine-5,3′-indoline]-2,2′,4-triones, spiro[benzothiazolo[2,3-b]quinazolin-5,3′-indoline]-2′,4-diones and spiro[benzothiazolo[2,3-b]pyrano[3,4-e]pyrimidine-5,3′-indoline]-2′,4-diones incorporating medicinally privileged heterosystems have been synthesized by an environmentally benign, efficient and convenient synthesis involving the sulfamic acid-catalyzed multicomponent domino reaction of 2-aminobenzothiazoles with isatin and cyclic 1,3-diketones in an aqueous medium.