Annulation of dihydroimidazoles: a 1,3-dipolar cycloaddition route to pyrrolo[1,2-a]imidazoles, pyrrolidines and pyrroles
作者:Raymond C. F. Jones、Kevin J. Howard、John R. Nichols、John S. Snaith
DOI:10.1039/a802048e
日期:——
4,5-Dihydroimidazolium ylides, formed by N-alkylation of 4,5-dihydroimidazoles, undergo diastereoselective endo 1,3-dipolar cycloaddition with electron-deficient alkene dipolarophiles to afford hexahydropyrrolo[1,2-a]imidazoles; reduction of the aminal functionality in the cycloadducts leads to substituted pyrrolidines. Cycloaddition using 2-chloropropenonitrile, followed by base treatment, affords pyrroles.
4,5-二氢咪唑鎓叶立德由4,5-二氢咪唑的N-烷基化形成,经历立体选择性的endo 1,3-偶极环加成反应与缺电子的烯烃偶极体,生成六氢吡咯并[1,2-a]咪唑;环加成产物中烯胺功能的还原得到取代的吡咯烷。使用2-氯丙烯腈进行环加成反应,随后进行碱处理,生成吡咯。