Metal-free anomalous [5+1] cycloaddition reactions of donor-acceptor aziridines for the synthesis of 2H-1,4-oxazines.

A new type of metal-free [5+1] cycloaddition reaction of donor-acceptor aziridines with 2-(2-isocyanoethyl)indoles is reported herein. This method exhibits broad substrate scope and atom-economy. A series of 2H-1,4-oxazines containing an indole heterocycle skeleton were obtained in up to 92% yield under mild reaction conditions. Control experiments revealed that free indole N-H is crucial for the above transformations. The theoretical calculation studies provided guidance on the in-depth insight into the reaction mechanism and the hydrogen-bond between the free indole N-H and carbonyl group was identified to lower the free energy barrier in the transition states.

Citation

Jianfeng Zheng, Jingzhi Bi, Lan Ma, Lvli Chen, Luhao Tang, Dong Xiong, Yin Tian. Metal-free anomalous [5+1] cycloaddition reactions of donor-acceptor aziridines for the synthesis of 2H-1,4-oxazines. Chemical communications (Cambridge, England). 2023 Jul 06;59(55):8572-8575

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PMID: 37338511

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