No abstract

C 14 H 19 NO 4

C 9 H 7 F 3 N 2 S, monoclinic, P2 1 /c (no. 14), a = 8.695 (4) Source of materialThe title compound was synthesized by addition of carbondisulfide (1.6 ml, 26 mmol) to the methanol solution (50 ml) of N-methyl-4-(trifluoromethyl)-1,2-benzendiamine (2.47 g, 13 mmol). The mixture solution was stirred at 0°C over night to give a colourless solution. The solution was evaporated to dryness getting a white solid (yield 70%). Colourless block crystals suitable for X-ray analysis of title compound were obtained from THF by slow evaporation within a few days. Experimental detailsThe H atoms were calculated geometrically and refined as riding, with C-H = 0.93-0.97 Å, except for H2, and with U iso (H) = 1.2U eq (parent atom). DiscussionBenzimidazole-2-thione and its derivatives have been widely studied because of their importance as pharmaceutical intermediates [1] and ligands [2,3]. X-ray structure analysis reveals that the title compound in the solid state prefers the thio form with N2 protonted rather than the alternative tautomeric ene-thiol form [4][5][6]. The bond length of C7-S1 is with a value of 1.673(3) Å slightly shorter than that in the nucleoside containing a benzimidazole (1.693 (4)

C 9 H 8 Br 2 O 3 ,orthorhombic, Pbca (no. 61), a =16.340(2) Å, Source of materialA N,N-dimethylformamide (DMF) solution (100 ml) of N-bromsuccinimide (NBS) (18.7g, 0.105 mol )was slowly droped into a DMF solution (20 ml) of ethyl 2-hydroxybenzoate (8.3g, 0.05 mol) with stirring. The resulting solution was continously stirred at room temperature over night. The mixture was poured into 500 ml cool water to produce the white precipitate. It was filtered, washed with cool water, and dried in air (yield 90%). Colourless block-shaped crystals suitable for structure analysis were obtained from ethanol by slow evaporation within afew weeks. Experimental detailsTheHatoms were calculated geometrically andrefined as riding, with C-H=0.93-0.97 Åwith U iso (H) =1.2U eq (parent atom). Positional parameters andthe U iso value of the HatomatO1were refined.

Source of material 4-Phenyl-5-(trifluoromethyl)thiophene-2-carboxylic acid was prepared by using 1,1,1-trifluoro-3-phenylpropan-2-one, phosphorous oxychloride and methyl 2-mercaptoacetate as raw materials according to the method of literature [1]. The colorless block-shaped crystals suitable for X-ray diffraction were obtained by slow evaporation of a methanol solution for a few days. Experimental detailsHydrogen atomes were positioned geometrically and allowed to ride on theier parent atoms with C-H = 0.93 Å, except for H1, H3 and H5 (U iso (H) = 1.2U eq (parent atom)).Discussion 2-Thiophenecarboxylic acid and its derivatives are important pharmaceutical intermediates [1]. In the crystal structure of the title compound, there are three crystallographically independent molecules. The bond distances and angles in these molecules are essentially the same within experimental error, but the dihedral angles between the phenyl and thiophene rings in these molecules display differences, with 43.10(8)°, 44.95(8)°and 38.99(9)°, respectively. Such differences also appear between carboxyl group and thiophene ring, with 2.8(2)°, 0.9(4)°and 9.4(1)°, respectively. In the thiophene ring the C-S distances are in the range of 1.705(2)-1.712(2) Å and the C-S-C angles are in the range of 90.5-90.7°, similar to other 2-thiophenecarboxylic acid compounds [2,3]. In the title structure, all molecules are connected to hydrogen-bonded dimers. Two crystallographic independent molecules are linked to each other with O1-H1···O4 (O···O = 2.640(2) Å, angle 174(3)°) and O3-H3···O2 (O···O = 2.646(2) Å, angle 178(3)°) form an asymmetric dimer. The third crystallographic independent molecule forms a dimer with a symmetry related molecule O5-H5···O6 (-x+1, -y+1, -z+1; O···O = 2.638(2) Å, O-H···O = 176(3)°).