Generation and trapping of 5,6-dimethylenepyrimidin-4-ones in Diels-Alder and Michael additions

Article abstract of DOI:10.1016/0040-4020(95)01008-4

Pyrimidone fused sulfones 5-7 were obtained from the reaction of amidines with 3-methoxycarbonyl-4-oxotetrahydrothiophene followed by N-methylation and oxidation with mCPBA. On heating in solution at 150°C, extrusion of SO₂ occurred to give the highly reactive 5,6-dimethylenepyrimidin-4-ones which were intercepted in situ in Diels-Alder reactions to give the adducts 24-28 and in conjugate addition reactions with thiol nucleophiles to give the thioethers 29 and 30.