Abstract
The title compounds, 4-(5-acetamido-3-acetyl-2-methyl-2,3-di-hydro-1,3,4-thia-diazol-2-yl)phenyl benzoate, C20H19N3O4S (I), 4-(5-acetamido-3-acetyl-2-methyl-2,3-di-hydro-1,3,4-thia-diazol-2-yl)phenyl isobutyrate 0.25-hydrate, C17H21N3O4S·0.25H2O (II), 4-(5-acetamido-3-acetyl-2-methyl-2,3-di-hydro-1,3,4-thia-diazol-2-yl)phenyl propionate, C16H19N3O4S (III) and 4-(5-acetamido-3-acetyl-2-methyl-2,3-di-hydro-1,3,4-thia-diazol-2-yl)phenyl cinnamate chloro-form hemisolvate, C22H21N3O4S·0.5CHCl3 (IV), all crystallize with two independent mol-ecules (A and B) in the asymmetric unit in the triclinic P space group. Compound II crystallizes as a quaterhydrate, while compound IV crystallizes as a chloro-form hemisolvate. In compounds I, II, III (mol-ecules A and B) and IV (mol-ecule A) the five-membered thia-diazole ring adopts an envelope conformation, with the tetra-substituted C atom as the flap. In mol-ecule B of IV this ring is flat (r.m.s. deviation 0.044 Å). The central benzene ring is in general almost normal to the mean plane of the thia-diazole ring in each mol-ecule, with dihedral angles ranging from 75.8 (1) to 85.5 (2)°. In the crystals of all four compounds, the A and B mol-ecules are linked via strong N-H⋯O hydrogen bonds and generate centrosymmetric four-membered R 4 4(28) ring motifs. There are C-H⋯O hydrogen bonds present in the crystals of all four compounds, and in I and II there are also C-H⋯π inter-actions present. The inter-molecular contacts in the crystals of all four compounds were analysed using Hirshfeld surface analysis and two-dimensional fingerprint plots.
Highlights
The title compounds, 4-(5-acetamido-3-acetyl-2-methyl-2,3-dihydro-1,3,4-thiadiazol-2-yl)phenyl benzoate, C20H19N3O4S (I), 4-(5-acetamido-3-acetyl-2methyl-2,3-dihydro-1,3,4-thiadiazol-2-yl)phenyl isobutyrate 0.25-hydrate, C17H21N3O4SÁ0.25H2O (II), 4-(5-acetamido-3-acetyl-2-methyl-2,3-dihydro1,3,4-thiadiazol-2-yl)phenyl propionate, C16H19N3O4S (III) and 4-(5-acetamido-3-acetyl-2-methyl-2,3-dihydro-1,3,4-thiadiazol-2-yl)phenyl cinnamate chloroform hemisolvate, C22H21N3O4SÁ0.5CHCl3 (IV), all crystallize with two independent molecules (A and B) in the asymmetric unit in the triclinic P1 space group
In the crystals of all four compounds, the A and B molecules are linked via strong N—HÁ Á ÁO hydrogen bonds and generate centrosymmetric four-membered R44(28) ring motifs
In molecules A and B of compounds I, II, III and molecule B of compound IV, the thiadiazole rings (S1/C3/N2/N3/C6) adopt envelope conformations, with atom C6 deviating from the mean plane of the remaining four atoms: by 0.132 (3) and
Summary
Nitrogen-containing heterocyclic compounds are one of the most important classes of biologically active compounds, exhibiting antimicrobial, antitumour and anti–inflammatory (Sethuram et al, 2013; Huq et al, 2010, Rajkumar et al, 2014, 2015; Thirunavukkarsu et al, 2017; Babu et al, 2014a,b) activities. Substituted 1,3,4-thiadiazoles that incorporate the toxiphoric —N C—S– linkage have attracted great attention owing to their broad spectrum of biological activities, including anti-inflammatory (Udupi et al, 2000), herbicidal antimicrobial, bactericidal (Tehranchian et al, 2005), antiviral and anti-HIV-1 (Invidiata et al, 1996) properties. Their action depends on the type and location of the polar substituents on the heterocyclic ring. The pharmacological effect of potential drugs depends on the stereochemistry and ring conformations. Recognizing the importance of such compounds in drug discovery and as part of our ongoing investigation of acetamide derivatives, the promising biological potency of 1,3,4thiadiazoles and variously substituted 1,3,4-thiadiazole frameworks, the title compounds have been prepared and their crystal structures are reported on
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