1620-21-9

Perazil,Burroughs-Wellcome,US,1949

H1-antihistamine

0.08 mol (19 9) of 4-chlorobenzhydryl chloride and 0.16 mol (16 g) of methylpiperazine were mixed in about 20 cc of dry benzene. The flask containing the reaction mixture was covered by a watch glass and set in a steam bath, and heating was continued for 6 hours. The contents of the flask were partitioned between ether and water and the ethereal layer was washed with water until the washings were neutral. The ethereal layer was extracted successively with 30 and 10 cc portions of 3 N hydrochloric acid. On evaporation of the ether layer there remained a residue of 2.5 9. The aqueous extracts were united and basified with concentrated alkali. The oily base was taken into ether and dried over potassium carbonate. On evaporation of the ether, N-methyl-N'-(4-chlorobenzhydryl) piperazine was recovered in the form of a viscous oil in 75% yield. The N-methyl-N'-(4-chlorobenzhydryl) piperazine was dissolved in absolute alcohol and ethanolic hydrogen chloride added in excess. The dihydrochloride crystallized on addition of absolute ether and was recrystallized from the same solvent mixture in the form of longish prisms melting at about 216°C.

Antihistaminic

Chlorcyclizinehydrochloride, 1-(p-chloro-α-phenylbenzyl)-4-methylpiperazinemonohydrochioride, is a light-sensitive, white crystallinepowder that is soluble in water (1:2), in alcohol(1:11), and in chloroform (1:4). A 1% solution has a pH between4.8 and 5.5. Disubstitution or substitution of halogenin the 2- or 3-position of the benzhydryl rings results in amuch less potent compound. Chlorcydizine is indicated forthe symptomatic relief of urticaria, hay fever, and certainother conditions.