A convenient synthesis of N-ethoxyphthalimido-3-methyl-4-substituted phenylpyrazolo[ 4ʹʹ,3ʹʹ5,6]pyrido[2,3-d] pyrimido[6,1-b]quinazolin-10-one via Niementowski reaction

Synthesis of 5-methyl-4-substitutedbenzylidene-2,4-dihydro-3H-pyrazol-3-one (3a-e) were achieved by the condensation reaction of 5-methyl-2,4-dihydro-3H-pyrazol-3-one (1) with various arylaldehyde (2a-e). Further compounds (3a-e) were converted into (4a-e) by treatment with malononitrile and ammonium acetate in ethanol. Compounds (4a-e) refluxed with formic acid to yield 3-methyl-4-(3-nitrophenyl)-1,6-dihydro-5H-pyrazolo[4ʹ,3ʹ:5,6] pyrido[2,3-d] pyrimidin-5-one (5a-e). After treatment of (5a-e) with phthalimidoxyethyl bromide (6) gave 1-N,6-N-diethoxyphthalimido-3-methyl-4-(4- substitutedphenyl)-5H-pyrazolo[4ʹ,3ʹ:5,6]pyrido[2,3-d]pyrimidin-5-one (7a-e). In another route compounds (8a-e) 3-methyl-4-substitutedphenyl-pyrazolo[4ʹ,3ʹ:5,6]pyrido[2,3-d]pyrimido[6,1-b]quinazolin-10-one were synthesized by a Niementowski reaction involving condensation of anthranilic acid with (5a-e) in polyphosphoric acid media via direct fusion and classical method. Compounds (8a-e) were treated with (6) to give the final compounds N-ethoxyphthalimido-3-methyl-4-substutitedphenyl-pyrazolo[4ʹ,3ʹ:5,6]pyrido[2,3-d]pyrimido [6,1-b]quinazolin-10-one (9a-e).