The unusual thermal transformations of the dimethyl 2,2,3,3-tetramethyl-7a-R-1,2,3,7a-tetrahydroimidazo[1,2-b]isoxazole-6,7-dicarboxylate derivatives
作者:Nikita V. Chukanov、Sergey A. Popov、Galina V. Romanenko、Vladimir A. Reznikov
DOI:10.1016/j.tet.2008.05.038
日期:2008.7
3-tetramethyl-7a-R-1,2,3,7a-tetrahydroimidazo[1,2-b]-isoxazole-6,7-dicarboxylate derivatives were shown to undergo thermal rearrangement along two competing routes giving rise to dimethyl 2-(2-R-4,5-dihydro-1H-3λ-5-imidazol-3-ylidene)-3-oxosuccinate derivatives and (or) dimethyl-2-oxo-3-(1-R-imidazolidin-2-ylidene)succinates. The latter undergoes intramolecular cyclization producing, in case of N-unsubstituted
二甲基2,2,3,3-四甲基-7a-R-1,2,3,7a-四氢咪唑并[1,2- b ]-异恶唑-6,7-二羧酸酯衍生物沿两种竞争路线进行热重排生成2-(2-R-4,5-二氢-1 H -3λ-5-咪唑-3-亚甲基)-3-氧代琥珀酸酯衍生物和(或)二甲基-2-氧代-3-(1- R-咪唑啉丁-2-亚基)琥珀酸酯。在N-未取代的衍生物的情况下,后者进行分子内环化,生成甲基5,6-二氧-1--1-R-2,3,5,6-四氢-1 H-吡咯并[1,2 - a ]咪唑-7 -羧酸盐。