Synthesis of chiral hexacyclic steroids via [8π + 2π] cycloaddition of diazafulvenium methides
作者:Susana M. M. Lopes、Cátia F. O. Correia、Sandra C. C. Nunes、Nelson A. M. Pereira、Ana R. F. Ferreira、Emanuel P. Sousa、Clara S. B. Gomes、Jorge A. R. Salvador、Alberto A. C. C. Pais、Teresa M. V. D. Pinho e Melo
DOI:10.1039/c5ob01110h
日期:——
First examples of [8π + 2π] cycloaddition of 16-dehydropregnenolone (16-DPA) acetate with diazafulvenium methides leading to chiral 4,5,6,7-tetrahydropyrazolo[1,5-a]pyridine-fused steroids are reported. These hexacyclic steroids were obtained exclusively or selectively with the approach of the 1,7-dipole by the less hindered α-face of 16-DPA. Quantum chemical calculations at the DFT level were carried
报道了乙酸16-脱氢孕烯醇酮(16-DPA)与二氮杂富烯鎓甲基化物导致手性4,5,6,7-四氢吡唑并[1,5 - a ]吡啶融合的类固醇的[8π+2π]环加成的第一个实例。这些六环类固醇是由1,7-偶极子通过16-DPA受阻较少的α面专门或选择性地获得的。为了使立体化学结果合理化,使用1-甲基-和1-苄基-二氮杂富烯基甲基与N-苯基马来酰亚胺的环加成作为模型反应,进行了DFT级的量子化学计算。结果表明,具有更稳定偶极构象的内环加成物(具有1-取代基朝外)比替代物更为有利。exo环加成。