Microwave-assisted three-component coupling-addition-S(N)Ar (CASNAR) sequences to annelated 4H-thiopyran-4-ones.

A whole family of annelated 4H-thiopyran-4-ones as the core structural unit was readily synthesized in good yields by a microwave-assisted coupling-addition-S(N)Ar (CASNAR) sequence starting from readily available (het)aroyl chlorides, alkynes and sodium sulfide nonahydrate in a consecutive one-pot three-component reaction. All representatives display a pronounced halochromicity of the absorption bands upon protonation. According to DFT calculations, the electronic ground state of the annelated 4H-thiopyran-4-ones possess a considerable zwitterionic character.