Year: 2023
Type: article
Abstract: Photochemical electrocyclization reactions are valued for both their ability to produce structurally complex molecules and their central role in elucidating fundamental mechanistic principles of photochemistry. We present herein a highly enantioselective 6π photoelectrocyclization catalyzed by a chiral Ir(III) photosensitizer. This transformation was successfully realized by engineering a strong hydrogen-bonding interaction between a pyrazole moiety on the catalyst and a basic imidazolyl ketone on the substrate. To shed light on the origin of stereoinduction, we conducted a comprehensive investigation combining experimental and computational mechanistic studies. Results from density functional theory calculations underscore the crucial role played by the prochirality and the torquoselectivity in the electrocyclization process as well as the steric demand in the subsequent [1,4]-H shift step. Our findings not only offer valuable guidance for developing chiral photocatalysts but also serve as a significant reference for achieving high levels of enantioselectivity in the 6π photoelectrocyclization reaction.
DOI: 10.1021/jacs.3c10782
Language: English
Subfield: Organic Chemistry
Field: Chemistry
Domain: Physical Sciences
Open Access status: green
Awards: A General Co-Catalytic Methodology for Enantioselective Photoredox Radical Cation Reactions, G1933497434, G2433956354, G3994591615, MRI: Acquisition of a modern single-crystal X-ray diffractometer with a high dynamic range detector, Laser-Enhanced NMR Instrumentation for Chemical and Biochemical Research, Towards Absolute Asymmetric Synthesis, QExactive (Orbitrap) mass spectrometer
OpenAlex ID: W4389340768