Stereoselective <i>N</i>-Heterocyclic-Carbene-Catalyzed Formal [4 + 2] Cycloaddition: Access to Chiral Heterocyclic Cyclohexenones
作者:Ladislav Lóška、Vojtěch Dočekal、Ivana Císařová、Jan Veselý
DOI:10.1021/acs.orglett.2c04021
日期:2023.1.13
alkenes containing a polarized double bond with an azolium-dienolate intermediate generated from α-bromo-α,β-unsaturated aldehydes without external oxidation of the Breslow intermediate. Heterocyclic cyclohexenones were produced in good isolated yields (typically about 90%) with good stereochemical outcomes (in most cases, dr > 20/1, and ee = 70–99%). The synthetic utility of the protocol was exemplified
本研究报告了一种不对称 NHC 催化的杂环烯烃的正式 [4 + 2] 环加成反应,该杂环烯烃含有极化双键和由 α-溴-α,β-不饱和醛生成的唑鎓-二烯醇中间体,无需 Breslow 中间体的外部氧化。杂环环己烯酮以良好的分离产率(通常约为 90%)和良好的立体化学结果(在大多数情况下,dr > 20/1,并且 ee = 70-99%)产生。该协议的综合效用以杂环烯烃的范围为例。