Reaction of 3-ethyl-5-aryl-1, 3, 4-oxadiazolium salts (X) with dialkyl acylphosphonates (V) in the presence of triethylamine afforded 2-aryl-4-ethyl-6-alkyl (or aryl)-5, 6-dihydro-4H-1, 3, 4-oxadiazin-5-one derivatives (XII) via an acyclic intermediate (XI) which is a 1 : 1 adduct of X and V. The mechanism of this novel reaction involving ring expansion is discussed briefly.
3-乙基-5-芳基-1,3,4-恶二唑鎓盐(X)与酰基
膦酸二烷基酯(V)在
三乙胺存在下反应,得到2-芳基-4-乙基-6-烷基(或芳基)-5 , 6-二氢-4H-1, 3, 4-恶二嗪-5-酮衍
生物 (XII) 通过无环中间体 (XI) 生成,该中间体是 X 和 V 的 1:1 加合物。这种涉及扩环的新反应的机理进行了简要讨论。