Studies on Seven-membered Ring Compounds. XXV. Chlorination of Cycloheptimidazol-2 (1H)-one Derivatives

Abstract

Chlorination of cycloheptimidazol-2 (1H)-one (I) and 6-hydroxy derivative (XII) with phosphoryl chloride in the presence of various bases was examined. Reexamination of the pubilshed procedure for the chlorination of I in the presence of pyridine mainly gave a hitherto unreported product, 2-(1, 4-dihydropyridino) cycloheptimidazole (V), and the reported 2-chlorocycloheptimidazole (II) was obtained only in a poor yield. By the modified procedure, 1-(2-cycloheptimidazolyl) pyridinium chloride (VIII) and the pyridinium salt (XV) were obtained from I and XII, respectively, and the treatment of VIII with alkali solution gave V. When the chlorination was carried out in the presence of dimethylaniline, the attack of dimethylaniline in the para-position or nitrogen occurred, and consequently, 2-(N-methylanilino) cycloheptimidazole (XVI), 2-chloro-4 (and 6-)-(p-dimethylaminophenyl) cycloheptimidazole (XVIII and XIX) were obtained from I, and 2-chloro-6-(N-methylanilino) cycloheptimidazole (XXVI) and 2, 6-dichloro-4-(p-dimethylaminophenyl) cycloheptimidazole (XXVII) from XII, respectively. The use of diethylaniline in the chlorination of I prevented the side reaction and II was obtained in a good yield.