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

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.

5-(4-Methoxyphenyl)-1-[4-(4-methoxyphenyl)thiazol-2-yl]-3-[4-(prop-2-ynyloxy)phenyl]-4,5-dihydro-1H-pyrazole

“…The design, efficient synthesis and molecular docking of some thiazolyl-pyrazole derivatives as anticancer reagents have been reported (Sayed et al, 2019). We have recently reported the formation of 1-(thiazol-2-yl)-4,5-dihydropyrazoles from simple precursors: synthesis, spectroscopic characterization and the data reports structures of an intermediate and two products (Mahesha et al, 2021). A series of 1,3-thiazole integrated pyrazoline scaffolds have been synthesized and characterized (CSD refcodes DADQIL, DADQEH; Salian et al, 2017).…”

Foreword to the special virtual issue in tribute to Jerry P. Jasinski

“…We were especially pleased to see that four of the articles had direct contributions from Jerry himself, as well as some of his former students and postdocs from Keene State College. The topical coverage of the articles spans the full spectrum of non-biological crystallography, including organic and main-group compounds (Thiruvalluvar et al, 2021;Mahesha et al, 2021;Allah et al, 2021;Malla et al, 2022;Rajegowda et al, 2021;Purdy et al, 2021), complexes of transition metals and lanthanides (Addison et al, 2022;Frey et al, 2021;Ullery et al, 2021;Sghyar et al, 2021;Tinapple et al, 2021;Mikhalyova et al, 2022;Pavlischuk et al, 2021), transition metal and actinide clusters (Park et al, 2022;Patel et al, 2022;Kelley et al, 2021), and coordination polymers (Lobana et al, 2022). It also includes two articles (Foxman, 2021;Zheng & Campbell, 2021) first published as part of the 'Modern approaches and tools for teaching crystallography' special issue in Acta E that describe the tutorial for teaching space groups and crystallographic symmetry that Jerry developed with Bruce Foxman.…”