[2 + 2] Cycloaddition/Retro-Electrocyclization/Decarboxylation Reaction Sequence: Access to 4-Aminopyridines from Methylideneisoxazolones and Ynamines.

Autor:	Galenko EE; Institute of Chemistry, St. Petersburg State University, 7/9 Universitetskaya nab., St. Petersburg 199034, Russia., Novikov MS; Institute of Chemistry, St. Petersburg State University, 7/9 Universitetskaya nab., St. Petersburg 199034, Russia., Khlebnikov AF; Institute of Chemistry, St. Petersburg State University, 7/9 Universitetskaya nab., St. Petersburg 199034, Russia.
Jazyk:	angličtina
Zdroj:	The Journal of organic chemistry [J Org Chem] 2023 Jul 07; Vol. 88 (13), pp. 8854-8864. Date of Electronic Publication: 2023 Jun 23.
DOI:	10.1021/acs.joc.3c00654
Abstrakt:	4-(1-Aminoallylidene)isoxazol-5-ones were synthesized in good yields by the [2 + 2]cycloaddition-retro-electrocyclization reaction of 4-methylideneisoxazol-5(4 H )-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 H )-ones and ynamines by the one-pot protocol.
Databáze:	MEDLINE
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