Stereochemical Course of Wittig Rearrangements of Dihydropyran Allyl Propargyl Ethers
作者:Minoru Isobe、Wei-Chung Chang、Pei-Kang Tsou、Chatchawan Ploysuk、Chin-Hui Yu
DOI:10.1021/acs.joc.5b00678
日期:2015.6.19
conformational inversion during the rearrangement, and (4) concerted [2,3]- or [1,2]-Wittig rearrangement. In some cases, a stepwise mechanism that involves the allyl-C–O bond cleavage is shared as the first step by both the [2,3]- and [1,2]-Wittig rearrangements. The stereochemical courses of the rearrangements are compared among the lithiated reactants to determine the reaction pathways. These mechanisms in the
已经研究了位于2-或4-位的糖衍生的二氢吡喃烯丙基炔丙基醚的[2,3] -Wittig重排,作为通过手性转移延伸4-或2-位碳链的有用手段。这些反应的立体化学过程取决于以下因素:(1)pro - R或pro - S的去质子化-H,(2)锂化的立体异构碳负离子的平衡,(3)重排过程中的构象倒置,以及(4)协同的[2,3]-或[1,2] -Wittig重排。在某些情况下,第一步涉及[2,3]-和[1,2] -Wittig重排,这是涉及烯丙基-C-O键断裂的逐步机理。在锂化的反应物中比较重排的立体化学过程,以确定反应途径。DFT计算进一步支持了多加氧二氢吡喃环系统中的这些机理。