Structure of 5-chloro-2-{3-[(diethylamino)methyl]-5-methyl-4H-1,2,4-triazol-4-yl}benzophenone (I) and of its methylamino analogue (II)

Abstract

Abstract. (I)C21H23C1N40Introducti on. Certain N-alkylaminobenzophenones, which may be considered as open-ring analogues of benzodiazepines, have been found to possess anxiolytic activity. In general this activity, as measured by the pentylene-tetrazole and other tests, is comparable to that of the analogous benzodiazepine (Gall, Hester, Rudzik & Lahti, 1976). However, the benzophenones show a low affinity for the benzodiazepine receptor in vitro (Hirai, Ishiba, Sugimoto, Fujishita, Tsukinoki & Hirose, 1981). Lahti & Gall (1976) and Hirai, Fujishita, Ishiba, Sugimoto, Matsutani, Tsukinoki & Hirose (1982) have suggested that benzophenones of this type can act as prodrugs, undergoing N-dealkylation and ring closure in vivo to form the corresponding benzodiazepine. The observed pharmacological activity of these benzophenones may therefore be due to the formation of active benzodiazepines rather than to any intrinsic activity of their own. We now report the crystal * Contribution from the Crystallography Unit, Universities of Aston and Birmingham. structures of the title compounds which, in the pentylene-tetrazole test, have activity comparable to that of alprazolam (IlI),t their benzodiazepine analogue. ~R CI.~ o RExperi mental .Compound (I): crystals were grown from amyl acetate/ethanol. A crystal of size 0-15 × 0-15 x 0.3 mm was mounted on an Enraf-Nonius CAD-4 diffractometer; cell dimensions from setting angles of 24 reflections having 8 < 0 < 12 °. Data collection by at--20 scans, 2 < 0 < 25°; two standard reflections measured every 2 h showed no significant variation; 3757 reflections scanned, 3515 unique, Rin t = 0.026; of these 795 having I>2"5~r(/) were considered observed and used in the analysis, index range -10___h<_10, 0___k<16, 0___1_32; no absorption corrections applied.Structure determined by direct methods; fullmatrix least-squares refinement on F magnitudes; owing to poor quality of data only C1, N and O atoms refined with anisotropic temperature factors, C atoms treated isotropically; H atoms placed in calculated positions riding on their respective bonded atoms, overall temperature factor refined to 0" 11 (2) A z for methyl H atoms and to 0.