Allen Meredith A, Ivanovich Ryan A, Beauchemin André M
Centre for Catalysis Research and Innovation, Department of Chemistry and Biomolecular Sciences, University of Ottawa, 150 Louis-Pasteur Pvt, Ottawa, ON, K1N 6N5, Canada.
Angew Chem Int Ed Engl. 2020 Dec 14;59(51):23188-23197. doi: 10.1002/anie.202007942. Epub 2020 Oct 7.
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.
1,3-偶极子常用于[3+2]环加成反应，而异电子中性偶极子变体仍未得到充分发展。与传统的1,3-偶极子不同，中性偶极子等价物形成两性离子环加成产物，可用于构建更复杂的分子结构。在本工作中，通过实验和密度泛函理论（DFT）计算研究了氧取代异氰酸酯（O-异氰酸酯）的首次环加成反应。这种独特的环加成策略通过与烯烃的分子内和分子间环加成反应，提供了一种获得新型杂环氮杂氧鎓叶立德的方法。这使得对瞬态氮杂氧鎓叶立德中间体的反应活性进行系统研究成为可能，该中间体可发生N-O键断裂，随后进行氮烯C-H插入反应，并在改变烯烃或O-异氰酸酯试剂结构时形成β-内酰胺或异恶唑烷酮。
