Sodium Hydroxide → 4,9-Dihydro-4-methyl-9-oxo-pyrazolo[5,1-b]quinazoline-2-carboxylic Acid

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Reaction Steps

A mixture of 5.8 g of 4,9-dihydro-4-methyl-9-oxo-pyrazolo[5,1-b]quinazoline-2-carboxylic acid, ethyl ester, 50 ml of 1 N aqueous sodium hydroxide and 400 ml of methanol is heated at reflux until complete solution is attained (about 30 minutes). The solution is evaporated at reduced pressure to remove methanol; the residue is diluted with water and acidified with 1 N hydrochloric acid. The resulting precipitate is 4,9-dihydro-4-methyl-9-oxo-pyrazolo[5,1-b]quinazoline-2-carboxylic acid is collected by filtration, washed with water and dried; mp 265° C., after crystallization from dimethylformamide/methanol.

Provenance & Evidence