One of the methods of producing an N-heterocyclic ring involves the condensation of ethoxymethylenemalonate with a primary amine and subsequent ring closure. This method has been employed with 8-amino-4-methylcinnoline in the synthesis of substituted pyrido[3,2-Zi]cinnolines.4-Methylcinnoline (I) was prepared, in good yield, according to the directions of Jacobs, et al. (1). Nitration of I (2) gave 4-methyl-8-nitrocinnoline (II).Reduction of II was accomplished by three different methods: A. Stannous chloride and hydrochloric acid (3); B. "Etched" iron and aqueous ethanol (4); C. Raney nickel and hydrogen at 45 pounds pressure. The best yields were obtained using the stannous chloride procedure; however, the ease of isolating the product made the "etched" iron method preferable when large amounts of nitro compound were used. SUMMARY 1. The synthesis of several substituted pyrido[3,2-A]cinnolines is reported.2. The ultraviolet spectrum of three cinnoline derivatives in ethanol solution is given.
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