TY - JOUR

T1 - Transformation of fluorinated 1,2-phenylenediamines in polyphosphoric acid medium with or without the benzimidazole 2-carboxylic acid: synthesis of fluorinated 2,2′-bibenzimidazoles and phenazine-2,3-diamines

AU - Li, Jiayao

AU - Krasnov, Vyacheslav I.

AU - Karpova, Elena V.

AU - Andreev, Rodion V.

AU - Shundrina, Inna K.

AU - Bagryanskaya, Irina Yu

AU - Selivanova, Galina A.

N1 - No data was used for the research described in the article. The authors thank V. Romanov for synthesis of 3,5-difluoro-1,2-phenylenediamine and 3,4,5,6-tetrafluoro-1,2-phenylenediamine. The investigation was carried out with the financial support of the Ministry of Education and Science of the Russian Federation. Jiayao Li thanks the China Scholarship Council for financial support. Authors would like to acknowledge the Multi-Access Chemical Research Center SB RAS for spectral and analytical measurements.

PY - 2024/7

Y1 - 2024/7

N2 - A series of asymmetrically fluorinated 2,2′-bibenzimidazoles were obtained by reaction of benzimidazole-2-carboxylic acid with fluorinated 1,2-phenylenediamines in polyphosphoric acid at elevated temperature. The tautomers of fluorinated 2,2′-bibenzimidazoles with a predominance of isomers containing F atoms in distant position relative to the NH group of the benzimidazole fragment are detected in DMSO‑d6 using NMR spectroscopy. The ratio of tautomers depends on the number and arrangement of F atoms in the initial fluorinated 1,2-phenylenediamines. Under similar conditions fluorinated 1,2-phenylenediamines in the presence of benzimidazole-2-carboxylic acid, but without its participation as well as without it, give fluorinated phenazine-2,3-diamines. The direction of transformation of fluorinated 1,2-phenylenediamines depends on the number and position of F atoms. Under similar conditions phenazine-2,3-diamine is not formed from non-fluorinated 1,2-phenylenediamine, but it is obtained with the presence of fluorinated 1,2-phenylenediamines. When fluorinated 1,2-phenylenediamines contain F atoms simultaneously at the positions 4 and 5, the hydrodefluorination of initial fluorinated 1,2-phenylenediamines occurs, resulting in less fluorinated 2,2′-bibenzimidazoles and phenazine-2,3-diamines. Hydrodefluorination of fluorinated 1,2-phenylenediamines in a polyphosphoric acid at elevated temperatures is the first example of the hydrodefluorination of fluorinated aromatic compounds containing strong donor substituents, such as amino groups. Polyphosphoric acid is shown to be a suitable medium for redox processes.

AB - A series of asymmetrically fluorinated 2,2′-bibenzimidazoles were obtained by reaction of benzimidazole-2-carboxylic acid with fluorinated 1,2-phenylenediamines in polyphosphoric acid at elevated temperature. The tautomers of fluorinated 2,2′-bibenzimidazoles with a predominance of isomers containing F atoms in distant position relative to the NH group of the benzimidazole fragment are detected in DMSO‑d6 using NMR spectroscopy. The ratio of tautomers depends on the number and arrangement of F atoms in the initial fluorinated 1,2-phenylenediamines. Under similar conditions fluorinated 1,2-phenylenediamines in the presence of benzimidazole-2-carboxylic acid, but without its participation as well as without it, give fluorinated phenazine-2,3-diamines. The direction of transformation of fluorinated 1,2-phenylenediamines depends on the number and position of F atoms. Under similar conditions phenazine-2,3-diamine is not formed from non-fluorinated 1,2-phenylenediamine, but it is obtained with the presence of fluorinated 1,2-phenylenediamines. When fluorinated 1,2-phenylenediamines contain F atoms simultaneously at the positions 4 and 5, the hydrodefluorination of initial fluorinated 1,2-phenylenediamines occurs, resulting in less fluorinated 2,2′-bibenzimidazoles and phenazine-2,3-diamines. Hydrodefluorination of fluorinated 1,2-phenylenediamines in a polyphosphoric acid at elevated temperatures is the first example of the hydrodefluorination of fluorinated aromatic compounds containing strong donor substituents, such as amino groups. Polyphosphoric acid is shown to be a suitable medium for redox processes.

KW - Asymmetrically fluorinated 2,2′-bibenzimidazole

KW - Fluorinated 1,2-phenylenediamine

KW - Fluorinated Phenazine-2,3-diamine

KW - Polyphosphoric acid

UR - https://www.scopus.com/record/display.uri?eid=2-s2.0-85198154088&origin=inward&txGid=52cfdac9df6a8958c864fc8e9df2223f

UR - https://www.mendeley.com/catalogue/a1767b51-e051-33b7-bcf4-e3f26017134c/

U2 - 10.1016/j.jfluchem.2024.110313

DO - 10.1016/j.jfluchem.2024.110313

M3 - Article

VL - 277

JO - Journal of Fluorine Chemistry

JF - Journal of Fluorine Chemistry

SN - 0022-1139

M1 - 110313

ER -