Crystal structure determination of N- and O-alkylated tautomers of 1-(2-pyridinyl)-5-hydroxypyrazole

Venkata S. Sadu, Yoon Mi Choi, Koteswara R. Kamma, Chong Hyeak Kim, Yun Soo Bae, Kee In Lee

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The crystal structure determination of tautomeric products produced by the alkylation of 1-(2-pyridinyl)-3-phenyl-4-propyl-1H-5-hydroxypyrazole 2 was investigated. Treatment of 2 with isopropyloxycarbonyloxymethyl iodide and potassium carbonate under phase-transfer conditions affords two major products out of three possible O-, N-, and C-alkylated tautomers. The tautomeric structures of O-alkylated 3a and N-alkylated 3c were elucidated by means of NMR spectroscopic investigations and confirmed by single crystal X-ray analysis. The single crystal structures of alkylated compounds provide clear difference between the tautomeric pyrazole and pyrazolone ring systems in terms of bond lengths and torsional angles, moreover, conformational changes between two tautomers.

Original languageEnglish
Article number128272
JournalJournal of Molecular Structure
StatePublished - 5 Sep 2020

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  • 1-(2-Pyridinyl)-5-hydroxypyrazole
  • C NMR
  • Crystal structure
  • N-Alkylation
  • O-Alkylation
  • Tautomerism


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