Two-Carbon Ring Expansion of Cyclobutanols to Cyclohexenones Enabled by Indole Radical Cation Intermediate: Development and Application to a Total Synthesis of Uleine
作者:Alexandre Leclair、Qian Wang、Jieping Zhu
DOI:10.1021/acscatal.1c05621
日期:2022.1.21
A single-electron transfer (SET) oxidation of indole or benzo[b]thiophene to a radical cation reverses the intrinsic polarity of these π-excessive bicyclic heteroarenes. Here we report an oxidative two-carbon homologation of cyclobutanols to cyclohexenones under a visible-light photoredox catalysis. 1-(Indol-2-yl)cyclobutan-1-ols are converted to 2,3,4,9-tetrahydro-1H-carbazol-1-ones, important structural
吲哚或苯并[ b ]噻吩到自由基阳离子的单电子转移 (SET) 氧化反转了这些 π-过量双环杂芳烃的固有极性。在这里,我们报告了在可见光光氧化还原催化下环丁醇与环己烯酮的氧化二碳同系化。1-(Indol-2-yl)cyclobutan-1-ols 转化为 2,3,4,9-tetrahydro-1 H -carbazol-1-ones,这是在生物碱和药物中发现的重要结构基序,具有广泛的底物范围. 一项机理研究表明,该反应由 SET 引发,从吲哚到激发的吖啶盐生成自由基阳离子,随后发生两次连续的 1,2-烷基迁移和再芳构化。苯并[ b]噻吩取代的环丁醇类似地转化为2,3-二氢二苯并[ b,d ]噻吩-4(1 H )-酮。记录了具有这种扩环过程的 (±)-uleine 的全合成。