An unusual azomethine ylid 1,3-dipole was generated on the periphery of pyrido[1,2,3-de]quinoxaline ring. This peripheral ylid, anhydro 3H-pyrido[1,2,3-de]quinoxalinium hydroxide, reacted stereoselectively with electron-deficient cis olefins such as dimethyl maleate and N-substituted maleimides giving endo [4+2] cycloadducts as single products. With such a trans olefin as dimethyl fumarate, a mixture of two kinds of the [4+2] cycloadducts, 1-exo-2-endo- and 1-endo-2-exo cycloadduct, was formed. These cyclo-addition reactions have possibly proceeded in a concerted manner.
在
吡啶并[1,2,3-de]
喹喔啉环的外围生成了一个不寻常的偶氮甲基 1,3-二极。这种外围的酰基,即 3H-
吡啶并[1,2,3-de]
喹喔啉氢氧化物,可与
马来酸二甲酯和 N-取代马来
酰亚胺等缺电子顺式烯烃发生立体选择性反应,生成单个内[4+2]环加载产物。而在
富马酸二甲酯等反式烯烃中,则形成了两种[4+2]环加成产物的混合物,即 1-外向-2-内向和 1-内向-2-外向环加成产物。这些环加成反应可能是以协同方式进行的。