Sulfolene pyridinones as precursors for pyridinone ortho-quinodimethanes and their Diels–Alder adducts

2(1H)-Pyrazinones were converted into [3,4-b] and [3,4-c] sulfolene pyridinones 4 and 5, serving as precursors for the corresponding 3,4- and 5,6-dimethylene 2(1H)-pyridinone ortho-quinodimethanes. These were trapped by in situ reaction with dienophiles. Tethering of 4 also enabled intramolecular cycloaddition.