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Cyclocondensation of 2‐Hydroxyimino‐1‐(naphthalen‐1‐yl)butane‐1,3‐dione with Alkyl Hydrazines Leading to Substituted 4‐Nitrosopyrazoles
Author(s) -
Bobrov Pavel S.,
Kirik Sergei D.,
Krasnov Pavel O.,
Lyubyashkin Aleksey V.,
Suboch Georgiy A.,
Tovbis Mikhail S.
Publication year - 2020
Publication title -
chemistryselect
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.437
H-Index - 34
ISSN - 2365-6549
DOI - 10.1002/slct.202002574
Subject(s) - chemistry , alkyl , substituent , naphthalene , ring (chemistry) , conformational isomerism , butane , electrophile , medicinal chemistry , pyrazole , alkylation , organic chemistry , molecule , catalysis
Cyclocondensation of 2‐(hydroxyimino)‐1‐(naphthalen‐1‐yl)butane‐1,3‐dione with alkyl hydrazines leading to new 1‐alkyl‐3(5)‐methyl‐5(3)‐(naphthalene‐1‐yl)‐4‐nitrosopyrazoles is described. 8 previously unknown N‐alkyl‐4‐nitrosopyrazoles with a 1‐naphthalene substituent at the 3 or 5 position of the pyrazole ring were obtained as a result. It was found that yields of naphthyl‐substituted pyrazoles with N‐alkyl groups near the naphthalene substituent were significantly lower than for 3‐(naphthalen‐1‐yl)‐substituted pyrazoles. Particular yields of pairwise formed isomeric nitrosopyrazoles were associated with the different electrophilicity of the two carbonyl groups of the initial diketone. Using quantum chemical calculations by the DFT method B3LYP−D3/6‐311G(d,p), the potential energies of the various conformers were estimated to draw a conclusion about the preferred attack of alkyl hydrazine on the carbonyl group, associated with the naphthalene ring. 1 H NMR and 2D 1 H‐ 13 C HSQC spectra of the compounds confirmed this direction of the reaction. The crystal structures of the synthesized compounds were established by X‐ray powder diffraction technique. Crystal structure data were in agreement with quantum chemical calculations.