Year: 2025
Type: article
Abstract: In this study, we demonstrate that a visible-light-mediated energy transfer process can serve as a mechanistic probe in the Staudinger cyclization. Ikeda demonstrated that N-acyl enaminone substrates undergo diastereoselective cyclization to form β-lactams under UV irradiation. We reinvestigated this process, employing energy transfer catalysis and Hammett studies, which enabled us to conclude that these reactions proceed in the T 1 state via the formation of a zwitterionic intermediate. This is in contrast to previous explanations, which suggest that the reaction proceeds via the S 1 state and involves a ground-state open-shell biradical. In-depth computational investigations support the zwitterionic hypothesis, with the final ring-closing process being radical. The rate of intersystem crossing was found to be critical in controlling the geometry of the zwitterionic intermediate, being ultimately responsible for the observed diastereoselectivity. Finally, a crossover experiment confirms reversibility in formation of the zwitterionic intermediate, experimentally validating a long-standing hypothesis.
Source: Chem Catalysis
Language: English
Subfield: Organic Chemistry
Field: Chemistry
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $9,170
Funders: National Science Foundation, Foundation for the National Institutes of Health, China Scholarship Council, Gobierno de Aragón, National Institutes of Health, Engineering and Physical Sciences Research Council, Agencia Estatal de Investigación, National Institute of General Medical Sciences, Division of Chemistry, European Social Fund
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OpenAlex ID: W4413304731