Intramolecular 1,3-dipolar cycloadditions of dihydroimidazolium ylides: synthesis of pyrrolo[1,2,3-de]quinoxalines and imidazo[1,2-a]indoles
作者:Pedro M. J. Lory、Raymond C. F. Jones、James N. Iley、Simon J. Coles、Michael B. Hursthouse
DOI:10.1039/b605458g
日期:——
an intramolecular 1,3-dipolar cycloaddition reaction that affords (via a reaction cascade involving eliminative ring-opening, recyclisation and prototropic tautomerism) unexpected hexahydropyrrolo[1,2,3-de]quinoxaline products. Steric bulk in both the dihydroimidazole and the dipolarophile allows isolation of an imidazo[1,2-a]indole, the initial product of cycloaddition. When the bromomethyl ketone
用含烯烃的溴甲基酮进行4,5-二氢咪唑的N-烷基化反应以及用DBU处理如此形成的4,5-二氢咪唑鎓离子会引起分子内1,3-偶极环加成反应(通过涉及反应的级联反应)消除开环,环化和质子互变异构)意外的六氢吡咯并[1,2,3-de]喹喔啉产品。在二氢咪唑和亲二氟体中的立体异构体都可以分离出咪唑并[1,2-a]吲哚,这是环加成反应的初始产物。当溴甲基酮不包含其他官能团时,或者由于空间限制而抑制环加成时,二氢咪唑鎓离子会进行开环水解,然后对暴露的氨基酮进行环化,从而获得3-烷基-1-甲酰基哌嗪-2-酮或3-芳基-1-甲酰基-1,4,5,