Cyclopentene Annulations of Alkene Radical Cations with Vinyl Diazo Species Using Photocatalysis
作者:Francisco J. Sarabia、Qiankun Li、Eric M. Ferreira
DOI:10.1002/anie.201805732
日期:2018.8.20
A direct (3+2) cycloaddition between alkenes and vinyl diazo reagents using either Cr or Ru photocatalysis is described. The intermediacy of a radicalcation species enables a nucleophilic interception by vinyl diazo compounds, a departure from their traditional electrophilic behavior. A variety of cyclopentenes are synthesized using this method, and experimental insights implicate a direct cycloaddition
Radical Cation Diels–Alder Cycloadditions by Visible Light Photocatalysis
作者:Shishi Lin、Michael A. Ischay、Charles G. Fry、Tehshik P. Yoon
DOI:10.1021/ja2093579
日期:2011.12.7
Ruthenium(II) polypyridyl complexes promote the efficient radicalcation Diels-Alder cycloaddition of electron-rich dienophiles upon irradiation with visible light. These reactions enable facile [4 + 2] cycloadditions that would be electronically mismatched under thermal conditions. Key to the success of this methodology is the availability of ligand-modified ruthenium complexes that enable rational
钌 (II) 多吡啶基配合物在可见光照射下促进富电子亲二烯体的有效自由基阳离子 Diels-Alder 环加成反应。这些反应使 [4 + 2] 环加成能够在热条件下发生电子失配。这种方法成功的关键是配体修饰的钌配合物的可用性,这些配合物能够合理调整催化剂的电化学性能,而不会显着扰乱系统的整体光物理性能。
Radical Cation Cyclopropanations via Chromium Photooxidative Catalysis
作者:Francisco J. Sarabia、Eric M. Ferreira
DOI:10.1021/acs.orglett.7b01095
日期:2017.6.2
The chromium photocatalyzed cyclopropanation of diazo reagents with electron-rich alkenes is described. The transformation occurs under mild conditions and features specific distinctions from traditional diazo-based cyclopropanations (e.g., avoiding β-hydride elimination, chemoselectivity considerations, etc.). The reaction appears to work most effectively using chromium catalysis, and a number of
RadicalcationDiels–Alderreactions by titanium dioxide (TiO2) photocatalysis in lithium perchlorate/nitromethane solution are described. TiO2 photocatalysis promotes reactions between electron-rich dienes and dienophiles, which would otherwise be difficult to accomplish due to electronic mismatching. The reactions are triggered by hole oxidation of the dienophile and are completed by the excited
Catalytic Wittig Reactions of Semi- and Nonstabilized Ylides Enabled by Ylide Tuning
作者:Emma E. Coyle、Bryan J. Doonan、Andrew J. Holohan、Killian A. Walsh、Florie Lavigne、Elizabeth H. Krenske、Christopher J. O'Brien
DOI:10.1002/anie.201406103
日期:2014.11.17
The first examples of catalytic Wittigreactions with semistabilized and nonstabilized ylides are reported. These reactions were enabled by utilization of a masked base, sodium tert‐butyl carbonate, and/or ylide tuning. The acidity of the ylide‐forming proton was tuned by varying the electron density at the phosphorus center in the precatalyst, thus facilitating the use of relatively mild bases. Steric