6-endo Versus 5-exo radical cyclization: streamlined syntheses of carbahexopyranoses and derivatives by 6-endo-trig radical cyclization
作者:Ana M. Gómez、Maria D. Company、Clara Uriel、Serafín Valverde、J. Cristóbal López
DOI:10.1016/j.tetlet.2006.12.108
日期:2007.2
Three factors that can direct 6-endo radical cyclization over 5-exo ring closure: substitution at C-5, vinyl radical cyclization and ring strain, have been considered in the context of the preparation of carbapyranoses from carbohydrate derivatives. As a result, alkyl radicals in substrates containing a strain inducing 2,3-O-isopropylidene ring, and vinyl radical in non-strained compounds undergo a
在由碳水化合物衍生物制备咔喃吡喃糖的背景下,已经考虑到了可以在5- exo闭环上指导6-内基自由基环化的三个因素:在C-5处的取代,乙烯基自由基环化和环应变。其结果是,在含有应变诱导2,3-基板烷基ø异亚丙基环,和乙烯基非应变化合物自由基经历一个完全区域选择性6-内- trig的环闭合导致carbasugar衍生物。