Generation of 5,6-dimethylene-2(1H)-pyridinones from [3,4-b] sulfolene pyridinones and application in Diels–Alder reactions

2(1H)-Pyrazinones were converted into various [3,4-b] sulfolene pyridinones , serving as precursors for thermolytic conversion into the corresponding 5,6-dimethylene 2(1H)-pyridinone ortho-quinodimethanes. These were trapped in situ by reaction with various dienophiles. Tethering of precursor with a dienophilic side chain attached to the 7-position of the [3,4-b] sulfolene pyridinone also enabled intramolecular cycloaddition when no rearrangement by 1,5-H-shift was viable.