5-dioxo-4,5-dihydro-1H-pyrrole-2-carboxylates 2a,b led to substituted dimethyl 3,9-dioxo-1,5,7,11-tetrahydro-1H,7H-dipyrazolo[1,2-a;1′,2′-d][1,2,4,5]tetrazine-1,7-dicarboxylates 4a,b and methyl 2,5-dihydro-5-oxo-1H-pyrazole-3-carboxylates 5a,b as minor products. The structure of compound 4a was determined by X-ray crystallography. The proposed mechanism of this conversion includes generation of (N-
取代的甲基1-亚甲基
氨基-4,5-二氧代-4,5-二氢-1 H-
吡咯-2-羧酸酯2a,b的热解反应生成取代的二甲基3,9-二氧代-1,5,7,11-四氢甲基-1 H,7 H -dipyrazolo [1,2- a ; 1',2'- d ] [1,2,4,5]四嗪-1,7-二
羧酸盐4a,b和甲基2,5-二氢-作为次要产物的5-氧代-1 H-
吡唑-3-
羧酸酯5a,b。化合物4a的结构通过X射线晶体学确定。提议的这种转换机制包括生成(N-亚甲基
氨基)亚
氨基基
乙烯酮6a,b及其分子内转化为偶氮甲
亚胺-5-氧代-2,5-
二氢吡唑-1-甲基-2-化物7a,b,它们以头尾相接的方式进行二聚,得到产物4a,b b并部分
水解为化合物5a,b。