Formation of 1-(thiazol-2-yl)-4,5-dihydropyrazoles from simple precursors: synthesis, spectroscopic characterization and the structures of an intermediate and two products

Ninganayaka Mahesha, Hemmige S. Yathirajan, Holalagudu A. Nagma Banu, Balakrishna Kalluraya, Ravindranath S. Rathore, Christopher Glidewell

Research output: Contribution to journalArticlepeer-review

Abstract

Two new 1-(thiazol-2-yl)-4,5-dihydropyrazoles have been synthesized from simple precursors, and characterized both spectroscopically and structurally. In addition, two intermediates in the reaction pathway have been isolated and characterized, one of them structurally. The molecules of the intermediate (E)-1-(4-methoxyphenyl)-3-[4-(prop-2-ynyloxy)phenyl]prop-2-en-1-one, C19H16O3 (I), are linked by a combination of C-H⋯O and C-H⋯π(arene) hydrogen bonds to form ribbons. The products (RS)-5-(4-methoxyphenyl)-1-(4-phenythiazol-2-yl)-3-[4-(prop-2-ynyloxy)phenyl]-4,5-dihydro-1H-pyrazole, C28H23N3O2S (II), and (RS)-5-(4-methoxyphenyl)-1-[4-(4-methylphenyl)thiazol-2-yl]-3-[4-(prop-2-ynyloxy)phenyl]-4,5-dihydro-1H-pyrazole, C29H25N3O2S (III), are closely related-differing only by presence or absence of a methyl group at the arylthiazolyl substituent-and crystallize in an isomorphous setting. Both molecules contain an effectively planar dihydro-pyrazole ring, and possess an overall T-shaped structure, which is a characteristic of triaryl-substituted 4,5-dihydro-1-(thiazol-2-yl)pyrazole compounds. The crystal packing is characterized by intermolecular C-H⋯S and C-H⋯π (aryl/alkyne) interactions. A combination of two C-H⋯π(arene) hydrogen bonds links the product molecules into sheets.
Original languageEnglish
Pages (from-to)975-981
Number of pages7
JournalActa Crystallographica Section E: Crystallographic Communications
Volume77
Issue numberPart 10
Early online date10 Sept 2021
DOIs
Publication statusPublished - Oct 2021

Keywords

  • Crystal structure
  • Heterocyclic compounds
  • Hydrogen bonding
  • Molecular structure
  • NMR spectroscopy
  • Pyrazoles
  • Supramolecular assembly
  • Synthesis
  • Thiazoles

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