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Structurally diverse spiroheterocycles incorporating medicinally privileged heterosystems have been synthesized by a simple and convenient synthesis involving triethylamine catalyzed multicomponent domino reaction of 2-aminobenzothiazoles with isatin and cyclic 1,3-diketones.

Structurally diverse spiroheterocycles; spiro[pyrimido[2,1‐b]benzothiazole‐3,3′‐chromene]‐2′,4′‐dione, spiro[pyrimido[2,1‐b]benzothiazole‐3,5′‐pyrimidine]‐2′,4′,6′‐trione, and spiro[pyrimido[2,1‐b]benz‐thiazole‐3,2′‐cyclohexane]‐1′,3′‐dione have been synthesized by an environmentally benign, efficient, and facile one‐pot pseudo‐four component reaction of 2‐aminobenzothiazoles with aromatic aldehydes and cyclic β‐diketones in aqueous medium. The process involves hetero‐Diels–Alder cycloaddition and provides facile access to spiroheterocycles fused with potentially interesting biologically active scaffolds. The configuration of hetero‐Diels–Alder cycloadduct has been ascertained through density functional theory calculations.