Inter- and Intramolecular Differentiation of Enantiotopic Dioxane Acetals through Oxazaborolidinone-Mediated Enantioselective Ring-Cleavage Reaction: Kinetic Resolution of Racemic 1,3-Alkanediols and Asymmetric Desymmetrization of <i>M</i><i>eso</i>-1,3-polyols
作者:Toshiro Harada、Takayuki Egusa、Yasuto Igarashi、Motoharu Kinugasa、Akira Oku
DOI:10.1021/jo025944g
日期:2002.10.1
Acetals derived from racemic 1,3-alkanediols undergo kinetic resolution in chiral oxazaborolidinone-mediated ring-cleavage reaction with nucleophiles such as enol silanes and allylic silanes. Enantioselectivity of the reaction is affected by nucleophiles, the N-sulfonyl groups of oxazaborolidinones, and the substituents attached to the acetal carbon. For disubstituted acetals rac-1 and for trisubstituted
衍生自外消旋1,3-链烷二醇的缩醛在手性氧杂氮杂硼烷酮介导的与亲核试剂(例如烯醇硅烷和烯丙基硅烷)的环裂解反应中经历动力学拆分。反应的对映选择性受亲核试剂,草氮杂硼烷酮的N-磺酰基和与缩醛碳相连的取代基的影响。对于衍生自syn-2,4-二甲基-1,3-戊二醇的二取代乙缩醛rac-1和三取代乙缩醛rac-2,通过使用甲烯丙基硅烷7b,c作为亲核试剂与N-间甲氧杂氮杂硼硼烷酮4a结合可获得令人满意的对映选择性。 。另一方面,通过将甲硅烷基烯酮缩醛5e与N-甲苯磺酰氧杂硼硼烷酮4b组合使用,可以实现源自抗2,4-二甲基-1,3-戊二醇的三取代缩醛rac-3b的对映选择性反应。通过消旋缩醛的动力学拆分或对映异构体区分反应而优化的反应条件已成功地通过双缩醛衍生物的对位缩醛部分的分子内分化而成功用于meso-1,3-多元醇的不对称脱对称。环裂解反应作为前手性多元醇的对映选择性末端分化方法的实用性在戊醛