Hydrochloric Acid → Pirquinozol

Participants

Reaction Conditions

Reaction Steps

500 mg (0.0019 mole) of 5,6-dihydro-5-oxopyrazolo[1,5-c]quinazoline-2-carboxylic acid, ethyl ester, prepared as described in Example 2A, is suspended in 10 ml distilled tetrahydrofuran and treated with 99.6 mg (0.0039 mole or 2 equivalents) of 85% lithium borohydride at room temperature. The mixture is stirred overnight (~20 hours), cooled down to 0° C., treated with 4.5 ml of 1.0 N hydrochloric acid and stirred for 30 minutes. The mixture is then diluted with water (25 ml), stirred for 10 minutes and filtered. The white precipitates are dried in a vacuum oven at ~70° for 1.5 hours to give 344 mg of title compound, m.p. 289°-290°; 84% yield. An additional 31.3 mg is obtained from the filtrate on addition of an equal volume of methylene chloride.

Provenance & Evidence