Titanocene‐Catalyzed [2+2] Cycloaddition of Bisenones and Comparison with Photoredox Catalysis and Established Methods. Issue 26 (24th May 2021)

• Record Type: Journal Article
• Authors: Zhang, Zhenhua; Stückrath, Julius B.; Grimme, Stefan; Gansäuer, Andreas
• Is Part Of: Angewandte Chemie international edition. Volume 60:Issue 26(2021)
• Page Start: 14339
• Page End: 14344
• Publication Date: 2021-05-24
• Subjects: cyclization -- electron transfer -- homogeneous catalysis -- radicals -- titanium; Chemistry -- Periodicals; 540
• DOI: 10.1002/anie.202102739
• Languages: English
• ISSNs: 1433-7851

Abstract

Abstract: Cp2 Ti(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. Abstract : For [2+2] cycloaddition reactions of bisenones, higher yields and diastereoselectivities as well as greater substrate scope were observed under catalysis by Cp2 Ti(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.