Institute of Chemistry, St. Petersburg State University, 7/9 Universitetskaya nab., St. Petersburg 199034, Russia.
J Org Chem. 2023 Jul 7;88(13):8854-8864. doi: 10.1021/acs.joc.3c00654. Epub 2023 Jun 23.
4-(1-Aminoallylidene)isoxazol-5-ones were synthesized in good yields by the [2 + 2]cycloaddition-retro-electrocyclization reaction of 4-methylideneisoxazol-5(4)-ones with ynamines. The reaction mechanism and the absence of hetero-Diels-Alder cycloadducts were investigated by DFT calculations. 4-(1-Aminoallylidene)isoxazol-5-ones were found to be convenient substrates for the preparation of 4-aminopyridines under thermal metal-free conditions. The process proceeds via decarboxylative isomerization with cyclic amino groups and accompanied by partial dealkylation of acyclic amino groups. 4-Aminopyridines can also be prepared directly from 4-methylideneisoxazol-5(4)-ones and ynamines by the one-pot protocol.
4-(1-亚氨基烯丙基)异恶唑-5-酮可通过 4-亚甲基异恶唑-5(4)-酮与炔胺的[2+2]环加成-反电环化反应以良好的收率合成。通过 DFT 计算研究了反应机理和杂 Diels-Alder 环加成产物的缺失。发现 4-(1-亚氨基烯丙基)异恶唑-5-酮在热无金属条件下是制备 4-氨基吡啶的方便底物。该过程通过环状氨基的脱羧异构化进行，同时伴有非环状氨基的部分脱烷基化。4-氨基吡啶也可通过一锅法直接由 4-亚甲基异恶唑-5(4)-酮和炔胺制备。
