diexo-3-Aza-4-oxotricyclo[4.2.1.02,5]non-7-ene (1) reacted with carboximidic esters by ring expansion to yield tricyclic 5,6-dihydropyrimidin-4(3H)-ones 3; when the latter were refluxed in chlorobenzene solution, cyclopentadiene split off to give 2-alkyl, 2-aralkyl-, 2-cycloalkyl and 2-arylpyrimidin-4(3H)-ones 4a-h. This method, which is conveniently carried out in a "one-pot" reaction from 1, provides a good alternative pathway for the preparation of compounds 4.
二氧代-3-氮杂-4-氧代
三环[4.2.1.02,5]壬-7-烯(1)与羧
亚胺酯通过扩环反应生成
三环 5,6-二氢
嘧啶-4(3H)-酮 3;当后者在
氯苯溶液中回流时,
环戊二烯析出,生成 2-烷基、2-芳基、2-环烷基和 2-芳基
嘧啶-4(3H)-酮 4a-h。 这种方法可以方便地在 1 的基础上进行 "一锅 "反应,为制备化合物 4 提供了一个很好的替代途径。