Studies on Seven-membered Ring Compounds. XVI. Synthesis of 2-Substituted Cycloheptimidazole Derivatives

In order to obtain 2-substituted cycloheptimidazole, the reaction of 2-methoxytropone (I) with substituted guanidine and amidine was carried out. Reaction of I with monoalkylguanidine afforded a small amount of 2-alkylaminocycloheptimidazole besides 1-alkyl-2-imino-1,2-dihydrocycloheptimidazole. Reaction of 2-bromo-7-methoxytropone with monoalkylguanidine afforded 2-alkylamino-4-bromocycloheptimidazole and rearranged product, 2-amino-3-alkyl-4(3H)-quinazolinone. However, reaction of dialkylguanidine with I and 2-bromo-7-methoxytropone afforded only one product, 2-dimethylamino-and 2-dimethylamino-4-bromocycloheptimidazole, respectively. Reaction of aromatic amidine with I or 2-chlorotropone afforded 2-phenyl-and 2-pyridylcycloheptimidazole derivatives. Among cycloheptimidazole derivatives, 2-dimethylaminocycloheptimidazole has been found to undergo easily electrophilic substitution reaction, bromination and nitration.