title: The synthesis, structure and properties of N-acetylated derivatives of ethyl 3-amino-1H-pyrazole-4-carboxylate.
abstract: Ethyl 3-amino-1H-pyrazole-4-carboxylate (1) was yielded through total synthesis and reacted with acetic anhydride to give the acetylated products 2-6. Compounds 1-6 were studied with HPLC, X-ray, FT-IR, (1)H-NMR, (13)C-NMR and MS. Acetylation was carried out in solvents of various polarity, namely; chloroform; dioxane; DMF; acetic anhydride, at room temperature and at boiling points; and in the presence and absence of DMAP. The acetylated products are mainly nitrogen atoms in the ring. The position of the ring proton in the solution was based on NOESY; multinuclear HMBC, HSQC spectra and calculations. For equivalent amounts (1-1.5 mol) of acetic anhydride at room temperature two products of monoacetylation are produced in the ring: 2 and 3, ca. 2 : 1 and at the same time only small amount of the third product of monoacetylated, 5 in DMF, as well the product diacetylated, 4. The greatest amount of the product 4 is produced during the reaction with chloroform. However, in this solvent and in dioxane no product 5 is produced. Compound 2 is, largely, formed in dimethylformamide, in the presence DMAP, 0.2 eq. In the presence of this catalytic base, for the first hour, there is a mixture 2 and 3 to the ratio ca. 95 : 5. With 8 eq of Ac(2)O at reflux, after another hour, the compounds 3, 4 and 6 appear about equal amounts. After a longer time, the compound, which appears most in this mixture is triacetylated derivative 6. The structural and spectroscopic characteristics of compounds 1-6 have been given and the methods for their preparation have been provided.
authors.affiliation: Institute of Chemisty, University of Opole, Oleska 48, 45-052 Opole, Poland.
authors.forename: Anna
authors.initials: A
authors.lastname: Kusakiewicz-Dawid
authors.forename: Elzbieta
authors.initials: E
authors.lastname: Masiukiewicz
authors.forename: Barbara
authors.initials: B
authors.lastname: Rzeszotarska
authors.forename: Izabela
authors.initials: I
authors.lastname: Dybała
authors.forename: Anna Eugenia
authors.initials: AE
authors.lastname: Kozioł
authors.forename: Małgorzata Anna
authors.initials: MA
authors.lastname: Broda
mesh_terms: D015761:4-Aminopyridine / Q000031:analogs & derivatives; D000089:Acetic Anhydrides; D000107:Acetylation; D002384:Catalysis; D002851:Chromatography, High Pressure Liquid; D002855:Chromatography, Thin Layer; D018360:Crystallography, X-Ray; D007202:Indicators and Reagents; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D011720:Pyrazoles / Q000138:chemical synthesis* / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D013696:Temperature
chemical_list: D000089:Acetic Anhydrides; D007202:Indicators and Reagents; D011720:Pyrazoles; C520862:ethyl 3-amino-1H-pyrazole-4-carboxylate; C031800:acetic anhydride; D015761:4-Aminopyridine; C003885:4-dimethylaminopyridine