Synthesis of 1,2,4-triazino[5,6-b]- and imidazo[4,5-b]quinoline derivatives

Abstract

o -Nitrophenylpyruvic acid thiosemicarbazone ( I ) has been cyclized to 2-thio-5-( o -nitrobenzyl)-6-azauracil ( II ) which has been transformed in 5-( o -nitrobenzyl)-6-azauracil ( III ) by both oxidation, and methylation and hydrolysis of the 3-methylmercapto-6-( o -nitrobenzyl)-2,5-dihydro-1,2,4-triazin-5-one ( V ) formed. Reduction of derivative III with iron(II) hydroxide and cyclization of the amino derivative IV formed gives 2,3,4,10-tetrahydro-1,2,4-triazino[5,6- b ]quinolin-3-one ( VI ). Compound VI is transformed in acid medium to 1-amino-1,2-dihydroimidazo[4,5- b ]quinolin-2-one ( VIII ) via the tautomer VII , and in boiling acetic acid it gives the acetylamino derivative IX . The N-amino derivative VIII reacts with carbonyl compounds to give the corresponding hydrazones X - XII , and its nitrosation gives 1,2-dihydroimidazo[4,5- b ]quinolin-2-one ( XIII ).