1,2-Dihydro-1,3,2-diazasilines 2 are prepared from 4-amino-1-azadienes 1 and react with dialkyl acetylenedicarboxylates to produce six- and seven-membered heterocycles depending on the substitution pattern of 1. Highly functionalized pyridine-2-carboxylates 5 and 8,8a-dihydro-2H-furo [2,3-b][1,4]diazepin-2-ones 11 are formed starting from azadienes 1 with R3 = H and R2 = R3 = H, respectively. On heating diazepines 11 undergo ring-contraction to alkyl 4-hydroxy-5-(iminomethyl) pyridine-2-carboxylates 13 which can be hydrolyzed to the corresponding 5-formyl-4-hydroxypyridine-2-carboxylates 14.
1,2-二氢-1,3,2-二氮
硅烷2由4-
氨基-1-氮二烯1制备得到,并与二烷基
乙炔二
羧酸酯反应,根据1的取代模式生成六元和七元杂环。高度官能化的
吡啶-2-
羧酸酯5和8,8a-二氢-2H-
呋喃[2,3-b][1,4]二氮杂卓-2-酮11分别从R3 = H和R2 = R3 = H的氮二烯1开始形成。在加热条件下,二氮杂卓11发生环收缩生成烷基
4-羟基-5-(
亚胺基甲基)
吡啶-2-
羧酸酯13,后者可
水解为相应的5-甲酰基-4-
羟基吡啶-2-
羧酸酯14。