Cascade radical cyclisations leading to steroid ring constructions. Regio- and stereo-chemical studies using ester- and fluoro-alkene substituted polyene acyl radical intermediates
作者:Haydn M. Boehm、Sandeep Handa、Gerald Pattenden、Lee Roberts、Alexander J. Blake、Wan-Sheung Li
DOI:10.1039/b002999h
日期:——
the E-substituted diene selenyl ester 7 underwent sequential cyclisations in the presence of Bu3SnH-AIBN leading to the trans-decalone 8 exclusively, the corresponding Z- and E-isomers of the methoxycarbonyl-substituted diene 16, under similar conditions, gave rise to a 2∶1 mixture of the trans- and cis-decalones 17a and 17b respectively in 62–73% yield. Cyclisation of the triene selenoate 30 led to
的影响连续6-的区域选择性和立体选择性的结果的因素的研究内切- trig的多烯酰基自由基中间体的环化,从而导致萘烷酮,perhydrophenanthrone,和类固醇环结构中,已经进行了。因此,尽管在Bu 3 SnH-AIBN的存在下,E-取代的二烯硒基酯7经历了连续的环化作用,排他地导致了反式-十杂醇8,但是在相似的条件下,甲氧基羰基取代的二烯16的相应的Z-和E-异构体条件下,产生反式的2∶1混合物-和顺式十制alone头17a和17b的产率分别为62-73%。硒酸三烯酯30的环化产生单一三环产物,产率为57%,其通过X射线衍射分析建立了顺式,顺式,反式相对立体化学32。当用Bu 3 SnH–AIBN处理硒酸三苯炔酯41a–c的溶液时,它们分别经历三个6- endo - trig的级联反应,然后进行5- exo - dig环化反应,形成完整的类固醇环系统42,45和47,产率分别为2