title: Spiro-fused (C2)-azirino-(C4)-pyrazolones, a new heterocyclic system. Synthesis, spectroscopic studies and X-ray structure analysis.
abstract: Reaction of 1-substituted 4-acyl-5-hydroxy-3-methyl-1H-pyrazoles (2) with hydroxylamine gives the corresponding "oximes" 3, which are mainly present as (Z)-2,4-dihydro-4-[(hydroxyamino)methylene]-3H-pyrazol-3-ones. Treatment of compounds 3 with trichloroacetyl isocyanate/potassium carbonate in anhydrous diethyl ether affords 7-methyl-1,5,6-triazaspiro[2.4]hepta-1,6-dien-4-ones (4). The structure of compounds 4 was elucidated by means of single-crystal X-ray analysis (4f, 4h) and confirmed by NMR spectroscopic investigations ((1)H, (13)C).
authors.affiliation: Department of Pharmaceutical Chemistry, University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria. holzer@merian.pch.univie.ac.at
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Holzer
authors.forename: Rosa M
authors.initials: RM
authors.lastname: Claramunt
authors.forename: Marta
authors.initials: M
authors.lastname: Pérez-Torralba
authors.forename: Davide
authors.initials: D
authors.lastname: Guggi
authors.forename: Thomas H
authors.initials: TH
authors.lastname: Brehmer