3-Dialkylamino-1,2,4-triazoles via ZnII-Catalyzed Acyl Hydrazide-Dialkylcyanamide Coupling

Sevilya N Yunusova; Dmitrii S Bolotin; Vitalii V Suslonov; Mikhail A Vovk; Peter M Tolstoy; Vadim Yu Kukushkin

doi:10.1021/acsomega.8b01047

3-Dialkylamino-1,2,4-triazoles via Zn^II-Catalyzed Acyl Hydrazide-Dialkylcyanamide Coupling

ACS Omega. 2018 Jul 3;3(7):7224-7234. doi: 10.1021/acsomega.8b01047. eCollection 2018 Jul 31.

Authors

Sevilya N Yunusova¹, Dmitrii S Bolotin¹, Vitalii V Suslonov², Mikhail A Vovk², Peter M Tolstoy², Vadim Yu Kukushkin¹

Affiliations

¹ Institute of Chemistry, Saint Petersburg State University, Universitetskaya Nab. 7/9, Saint Petersburg 199034, Russian Federation.
² Center for X-ray Diffraction Studies, Center for Magnetic Resonance, Saint Petersburg State University, Universitetskii Pr., 26, Saint Petersburg 199034, Russian Federation.

Abstract

Zinc(II)-catalyzed (10 mol % ZnCl₂) coupling of acyl hydrazides and dialkylcyanamides in ethanol leads to 3-dialkylamino-1,2,4-triazoles (76-99%; 17 examples). This reaction represents a novel, straightforward, and high-yielding approach to practically important 3-NR₂-1,2,4-triazoles, which utilizes commercially available and/or easily generated substrates. Seventeen new 3-NR₂-1,2,4-triazoles were characterized by HRESI⁺-MS and IR, ¹H, and ¹³C{¹H} NMR spectroscopies and five species additionally by single-crystal X-ray diffraction (XRD). The Zn^II-catalyzed reaction proceeds via initial generation of the [Zn{RC(=O)NHNH₂}₃](ZnCl₄) complexes (exemplified by isolation of the complex with R = Ph, 76%; characterized by HRESI⁺-MS, IR, CP-MAS TOSS ¹³C{¹H} NMR, and XRD). Electronic effects of substituents at the acyl hydrazide moiety do not significantly affect the reaction rate and the yield of the target triazoles, whereas the steric hindrances reduce the reaction rate without affecting the yield of the heterocycles.