Titanocene‐Catalyzed [2+2] Cycloaddition of Bisenones and Comparison with Photoredox Catalysis and Established Methods
| Autor: | Andreas Gansäuer, Zhenhua Zhang, Julius B. Stückrath, Stefan Grimme |
|---|---|
| Rok vydání: | 2021 |
| Předmět: |
cyclization
010405 organic chemistry Chemistry Communication Radical Photoredox catalysis chemistry.chemical_element Homogeneous catalysis Radical Reactions General Medicine General Chemistry electron transfer radicals 010402 general chemistry Photochemistry homogeneous catalysis 01 natural sciences Communications Catalysis Cycloaddition 0104 chemical sciences Electron transfer titanium Titanium |
| Zdroj: | Angewandte Chemie (International Ed. in English) |
| ISSN: | 1521-3773 1433-7851 |
| Popis: | Cp2Ti(TFA) is a broadly applicable catalyst for the [2+2] cycloaddition of bisenones by inner‐sphere electron transfer. The attractiveness of this mechanism is shown by comparison with outer‐sphere ET methods. DFT calculations show that the reaction proceeds through a unique unfavorable 5‐exo (the rate‐determining step) and a favorable 4‐exo cyclization. For [2+2] cycloaddition reactions of bisenones, higher yields and diastereoselectivities as well as greater substrate scope were observed under catalysis by Cp2Ti(TFA) than with previously established methods (see scheme). The mechanism is characterized by a highly unusual combination of an unfavorable and rate‐determining 5‐exo and favorable 4‐exo cyclization, as established by DFT calculations. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|
Plný text