4-[(4-benzylphenyl)amino]-1-methyl-1H-pyrazole-5-carboxylic acid → 7-Benzyl-1-methyl-1,4-dihydro-pyrazolo[4,3-b]quinolin-9-one

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A mixture of 4-[(4-benzylphenyl)amino]-1-methyl-1H-pyrazole-5-carboxylic acid (EXAMPLE 11, step 1, 4.86 g, 15.81 mmol) in phosphorus oxychloride (40 ml) was refluxed for 3 h. After cooling to room temperature, the mixture was concentrated and dried in vacuo. The mixture was dissolved in ethyl acetate (300 ml), washed with water (100 ml) and saturated aqueous sodium bicarbonate (100 ml×2) and dried over magnesium sulfate. Removal of solvent gave the dark red residue, which was chromatographed on a column of silica gel eluting with ethyl acetate/hexane (1/3) to afford 3.86 g (79%) of the title compound as a yellow solid.

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