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. Issue 43 (17th October 2018)

• Record Type: Journal Article
• Authors: Fesenko, Anastasia A.; Grigoriev, Mikhail S.; Shutalev, Anatoly D.
• Is Part Of: Organic & biomolecular chemistry. Volume 16:Issue 43(2018)
• Page Start: 8072
• Page End: 8089
• Publication Date: 2018-10-17
• Subjects: Chemistry, Organic -- Periodicals; Bioorganic chemistry -- Periodicals; Chemistry, Physical organic -- Periodicals; 547
• DOI: 10.1039/c8ob01766b
• Languages: English
• ISSNs: 1477-0520

Abstract

Abstract : Stereoselective syntheses of 1-unsubstituted and 1-alkylsubstituted 1, 2, 4-triazepane-3-thiones/ones based on reduction or reductive alkylation of 2, 4, 5, 6-tetrahydro-3 H -1, 2, 4-triazepine-3-thiones/ones are reported. 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-3 H -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.