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.
嘧啶稠合的二氢
噻吩S,S-二氧化物7经过热消除
二氧化硫得到
嘧啶邻
喹啉甲烷8,可以在狄尔斯-阿尔德反应中截取,得到取代的5,6,7,8-四氢
喹唑啉;它们与更多的亲二烯体一起加热形成环辛基
嘧啶。