The reduction of 2-nitro-4,5-methylenedioxyacetophenone (I) with H2 over PtO2 in ethanol gives 2-amino-4,5-methylenedioxyacetophenone (II), which is cyclized by treatment with NaNO2 and HCl in water yielding 6,7-methylenedioxycinnolin-4-ol (III). The bromination of (III) with Br2 and potassium acetate in refluxing acetic acid affords 3-bromo-6,7-methylenedioxycinnolin-4-ol (IV), which is treated with Cu2(CN)2 in refluxing DMF giving 4-hydroxy-6,7-methylenedioxycinnolin-3-carbonitrile (V). Alkylation of (V) with ethyl iodide (A) by means of NaH in DMF affords 1-ethyl-6,7-methylenedioxy-4(1H)-oxocinnolin-3-carbonitrile (VI), which is finally hydrolyzed with HCl in refluxing acetic acid.