Stereoselective Synthesis of New 4-Aryl-5-indolyl-1,2,4-triazole S - and N -β-Galactosides: Characterizations, X-ray Crystal Structure and Hirshfeld Surface Analysis.

5-(1H-Indol-2-yl)-4-phenyl-2,4-dihydro-3H-1,2,4-triazole-3-thione 1a and 4-(4-chlorophenyl)-5-(1H-indol-2-yl)-2,4-dihydro-3H-1,2,4-triazole-3-thione 1b were galactosylated in the presence of NaHCO₃ in ethanol to produce S-galactosides 3,4, whereas, in the presence of K₂CO₃ in acetone they produced a mixture of S- and N-galactosides 3-6 with a higher yield of S-galactosides over the respective N-galactosides. Improvement in the yields of N-galactosides was produced by thermal migration of the galactosyl moiety from sulfur to nitrogen using fusion. β-Stereoselectivity of galactosylation was determined using the coupling constant value ³J_1,2, which exceeded 9.0 Hz in all prepared galactosides. The precursors 1a and 1b alkylated with 3-bromopropan-1-ol 7 in K₂CO₃ and acetone produced the S-alkylated products 8 and 9, respectively. Structural determinations of new compounds 5 and 9 are presented. The phenyl and indole moieties were found to be twisted from the triazole ring mean in both compounds. For compound 5, the twist angles were 66.24° and 18.86°, respectively, while the corresponding values for 9 were in the ranges of 73.15–77.29° and 13.96–20.70°, respectively. Hence, the crystal system of 9 is triclinic while the space group is P-1. Detailed analysis of the intermolecular interactions in the crystal structure of 5 is presented using Hirshfeld calculations. The O...H, N...H, C...H, and S...H contacts appeared as red spots in the d_norm Hirshfeld surface indicating short distance intermolecular interactions. Their percentages were estimated based on the decomposition of the fingerprint plot to be 25.6, 2.4, 14.0, and 6.3%, respectively. [ABSTRACT FROM AUTHOR]