10.1007/BF00506621
The research investigates the free-radical hydroxymethylation of benzimidazole derivatives and the condensation of 3,4-dicyano-5-aminopyrazole with ethyl orthoformate. In the hydroxymethylation study, benzimidazole derivatives such as 1-methylbenzimidazole and 1-phenylbenzimidazole were subjected to free-radical hydroxymethylation using ammonium persulfate in methanol and sulfuric acid, with silver ions as a catalyst to enhance yields. The study found that benzimidazole displayed lower activity than quinoline in the addition of the hydroxymethyl radical, and the yields of hydroxymethylation products were influenced by the ability of intermediate benzimidazolium cation radicals to undergo oxidation. In the condensation study, 3,4-dicyano-5-aminopyrazole was reacted with ethyl orthoformate under different conditions to produce compounds like N-ethyl-3,4-dicyano-5-ethoxymethyleneaminopyrazole and 3,4-dicyano-5-ethoxymethyleneaminopyrazole. The formation of these products and their subsequent conversion to pyrazolo[3,4-d]pyrimidines using a methanol solution of ammonia were also explored.