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O-Isocyanates as Uncharged 1,3-Dipole Equivalents in [3+2] Cycloadditions |
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| Authors: | Meredith A Allen Ryan A Ivanovich Dr André M Beauchemin |
| Institution: | 1. Centre for Catalysis Research and Innovation, Department of Chemistry and Biomolecular Sciences, University of Ottawa, 150 Louis-Pasteur Pvt, Ottawa, ON, K1N 6N5 Canada
These authors contributed equally to this work. co-first authors;2. Centre for Catalysis Research and Innovation, Department of Chemistry and Biomolecular Sciences, University of Ottawa, 150 Louis-Pasteur Pvt, Ottawa, ON, K1N 6N5 Canada |
| Abstract: | 1,3-Dipoles are commonly used in 3+2] cycloadditions, whereas isoelectronic uncharged dipole variants remain underdeveloped. In contrast to conventional 1,3-dipoles, uncharged dipole equivalents form zwitterionic cycloadducts, which can be exploited to build further molecular complexity. In this work, the first cycloadditions of oxygen-substituted isocyanates (O-isocyanates) were studied experimentally and by DFT calculations. This unique cycloaddition strategy provides access to a novel class of heterocycle aza-oxonium ylides through intramolecular and intermolecular cycloadditions with alkenes. This allowed a systematic study of the reactivity of the transient aza-oxonium ylide intermediate, which can undergo N−O bond cleavage followed by nitrene C−H insertion, and the formation of β-lactams or isoxazolidinones upon varying the structure of the alkene or O-isocyanate reagents. |
| Keywords: | [3+2] cycloaddition C−H amination isocyanates nitrenes oxycarbonylation |