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A convenient stereoselective access to novel 1,2,4-triazepan-3-ones/thiones via reduction or reductive alkylation of 7-membered cyclic semicarbazones and thiosemicarbazones

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Abstract

A general stereoselective approach to previously unknown 1,2,4-triazepane-3-thiones/ones based on reduction or reductive alkylation of readily available 2,4,5,6-tetrahydro-3H-1,2,4-triazepine-3-thiones/ones has been developed. The approach involved the treatment of tetrahydrotriazepines with sodium cyanoborohydride in MeOH at pH 3 or with sodium borohydride and excess of carboxylic acid in THF to give 1-unsubstituted or 1-alkyl-substituted 1,2,4-triazepane-3-thiones/ones, respectively. The latter were also prepared by the reaction of 1-unsubstituted 1,2,4-triazepane-3-thiones/ones with sodium cyanoborohydride and an aldehyde in MeOH in the presence of AcOH. The stereochemistry of the triazepane-3-thiones/ones obtained was established in DMSO solution and in the solid state using NMR spectroscopy and single-crystal X-ray diffraction. These data and DFT B3LYP/6-311++G(d,p) calculations show that the gauche effect plays a significant role in stabilization of preferred conformations of 1-unsubstituted 1,2,4-triazepane-3-thiones/ones.

Graphical abstract: A convenient stereoselective access to novel 1,2,4-triazepan-3-ones/thiones via reduction or reductive alkylation of 7-membered cyclic semicarbazones and thiosemicarbazones

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Publication details

The article was received on 23 Jul 2018, accepted on 08 Oct 2018 and first published on 09 Oct 2018


Article type: Paper
DOI: 10.1039/C8OB01766B
Citation: Org. Biomol. Chem., 2018, Advance Article
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    A convenient stereoselective access to novel 1,2,4-triazepan-3-ones/thiones via reduction or reductive alkylation of 7-membered cyclic semicarbazones and thiosemicarbazones

    A. A. Fesenko, M. S. Grigoriev and A. D. Shutalev, Org. Biomol. Chem., 2018, Advance Article , DOI: 10.1039/C8OB01766B

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