Pyrimidine o-quinodimethanes: Formation of 1:1 and 2:1 adducts with dienophiles

Article abstract of DOI:10.1016/0040-4039(93)88125-3

Pyrimidine fused dihydrothiophene S,S-dioxides 7 undergo thermal elimination of sulfur dioxide to give the pyrimidine o-quinodimethanes 8 which can be intercepted in Diels-Alder reactions to give substituted 5,6,7,8-tetrahydroquinazolines; these form cyclooctapyrimidines on heating with more dienophile.