The synthesis of ω‐dialkylaminoalkylaminopyrazino[2,3‐d]‐, pyrido[2,3‐d]‐, imidazo[4,5‐c]‐ and imidazo[4,5‐d]pyridazines

Abstract

Abstract The synthesis of 5‐chloro‐8‐(ω‐dialkylaminoalkylamino)pyrazino[2,3‐ d ]pyridazine (II) proceeded smoothly when 5,8‐dichloropyrazino[2,3‐ d ]pyridazine (I) was allowed to react with ω‐dialkylaminoalkylamines. Similarly, the reaction of 5,8‐dichloropyrido[2,3‐ d ]pyridazine (IV) with ω‐dialkylaminoalkylamines gave the two expected products 8‐chloro‐5‐(ω‐dialkylaminoalkylamino)pyrido[2,3‐ d ]pyridazine (V) and 5‐chloro‐8‐(ω‐dialkylaminoalkylamino)pyrido[2,3‐ d ]pyridazine (VI) in a 2:3 ratio. 4,7‐Dichloroimidazo[4,5‐ d ]pyridazine (XII) was found to be much less reactive towards nucleophilic substitutions and more vigorous conditions resulted in disubstituted products (XIII). 7‐Chloroimidazo[4,5‐ c ]pyridazine (XVIII) was also found to be much less reactive towards nucleophilic substitution. In both of these cases one of the imidazole nitrogen atoms was blocked by a tetrahydropyranyl group which increased the reactivities and led to the desired monosubstituted products XVII from XII and in the latter case the expected products (XIX).