Quinoxalines XV. Convenient synthesis and structural study of pyrazolo[1,5-a]quinoxalines.
A series of aryloxymethylquinoxaline oximes, hitherto unknown and synthesized from the corresponding aldehydes, afforded in only one step pyrazolo[1,5-a]quinoxalines in the presence of acetic anhydride at high temperatures. A formal [3,5]-sigmatropic rearrangement was proposed as the mechanistic rationale for this unprecedented transformation. Saponification with potassium hydroxide furnished the free phenol derivatives which were studied by NMR spectroscopy and accompanying theoretical DFT calculations, establishing intramolecular hydrogen bonding and the spatial magnetic properties. Additionally, mass spectrometric fragmentation was investigated by B/E-linked scans and collision-induced dissociation experiments. The fragmentation pattern devoted a new gas phase rearrangement process, which proved to be unique and characteristic for pyrazolo[1,5-a]quinoxalines.
Sarodnick
Gerhard
G
Department of Chemistry, University of Potsdam, Karl-Liebknecht-Str. 24-25, D-14476 Potsdam, Germany.
Linker
Torsten
T
Heydenreich
Matthias
M
Koch
Andreas
A
Starke
Ines
I
Fürstenberg
Sylvia
S
Kleinpeter
Erich
E
D006860:Hydrogen Bonding; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D008958:Models, Molecular; D008968:Molecular Conformation; D011720:Pyrazoles / Q000138:chemical synthesis / Q000737:chemistry*; D011810:Quinoxalines / Q000138:chemical synthesis / Q000737:chemistry*; D013816:Thermodynamics
D011720:Pyrazoles; D011810:Quinoxalines