Domino Reaction of Acyclic α,α‐Dialkenoylketene S , S ‐Acetals and Diamines: Efficient Synthesis of Tetracyclic Thieno[2,3‐ b ]thiopyran‐Fused Imidazo[1,2‐ a ]pyridine/Pyrido[1,2‐ a ]pyrimidines

A series of unusual fused tetraheterocyclic compounds 3 , consisting of a thiopyran (ring A), a thiophene (ring B), a pyridine (ring C), and an imidazole or a pyrimidine (ring D) core, with a bridgehead nitrogen and an angular methyl group, were successfully synthesized by a catalyst‐free, one‐pot, two‐component domino reaction of 4‐(4‐methyl‐1,3‐dithiol‐2‐ylidene)‐1,7‐bis(aryl/heteroaryl)hepta‐1,6‐diene‐3,5‐dione 2 and diamines. In this reaction, up to five new bonds were formed accompanied by the CS bond cleavage of the 1,3‐dithiole ring of 2 , with water as the only by‐product.