[Preparation and pharmacologic activity of 2-(4'R')benzyl-5R-benzimidazole and 2-(4'-pyridinyl)-5R-benzimidazoles. Analgesic activity and effect on conditioned avoidance response].

Sixteen 2-(4'R')phenyl-5R-benzimidazoles and two 2-(4'-pyridinyl)-5R-benzimidazoles were prepared and tested, together with 2-phenylbenzimidazole, for their activity on the acquisition of a conditioned avoidance response in rats and for analgesic activity in mice, and compared with chlorpromazine and acetylsalicylic acid. Several compounds inhibit strongly the acquisition of a C.A.R., with 2-(4'-alkoxy)phenylbenzimidazoles (XVI) and (XVII) clearly exceeding chlorpromazine. Analgesic activity is also generally present in the examined compounds; those bearing in the position 5 a trifluoromethyl or an acetyl group exhibit an activity higher than that of acetylsalicylic acid. Deconditioning and analgesic activities are not correlated with each other.