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 radicalcation 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。
Cascade Oxidative Dearomatization/Semipinacol Rearrangement: An Approach to 2-Spirocyclo-3-oxindole Derivatives
cascade reaction involving oxidative dearomatization/semipinacol rearrangement of indol‐2‐yl cyclobutanols is explored with N‐sulfonyloxaziridine (Davis oxaziridines) as oxidant, generating various 2‐spiroquaternary 3‐oxindoles in modest to good yields. This method might be useful in the synthesis of indole‐based alkaloids bearing 2‐spiroquaternary carbon centers. PTS=p‐toluenesulfonic acid monohydrate
Prochiral Diheteroaryl Sulfoxides and Their Reactions with (<i>S</i>)-Li<sub>2</sub>-BINOLate-Activated Diisobutylmagnesium
作者:Simon Ruppenthal、Reinhard Brückner
DOI:10.1002/ejoc.201701309
日期:2018.1.10
symmetric – i.e. prochiral – diheteroaryl sulfoxides. The latter were treated with a 0.5- or 1.2-fold molar amount of 5:4 mixtures of dilithium (S)-BINOLate and diisobutylmagnesium. This allowed five asymmetricsulfoxide/magnesium exchange reactions to occur. They delivered asymmetricsulfoxides in up to 77 % yield and with up to 88 % ee. Surprisingly, four related diheteroaryl sulfoxides, bis(2-pyridyl)
5 元环杂环被α-锂化或α-镁化,以便它们攻击SOCl2 或SO(OMe)2,形成对称的——即前手性——二杂芳基亚砜。后者用0.5-或1.2-倍摩尔量的5:4二锂(S)-BINOLate和二异丁基镁的混合物处理。这允许发生五个不对称的亚砜/镁交换反应。他们以高达 77% 的产率和高达 88% 的 ee 提供不对称亚砜。令人惊讶的是,四种相关的二杂芳基亚砜、双(2-吡啶基)亚砜和双(3-吡啶基)亚砜不适合这种交换,而是分解了。
Silylation of C–H bonds in aromatic heterocycles by an Earth-abundant metal catalyst
作者:Anton A. Toutov、Wen-Bo Liu、Kerry N. Betz、Alexey Fedorov、Brian M. Stoltz、Robert H. Grubbs
DOI:10.1038/nature14126
日期:2015.2.5
and complex molecule synthesis, because these compounds have very useful physicochemical properties. Many of the methods now used to construct heteroaromatic C–Si bonds involve stoichiometric reactions between heteroaryl organometallic species and silicon electrophiles or direct, transition-metal-catalysed intermolecular carbon–hydrogen (C–H) silylation using rhodium or iridium complexes in the presence