Hydrochloric Acid → 2,4-Diamino-5-methylquinazoline-6-carbonitrile

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Under a nitrogen atmosphere, a stirred solution of 2.5 grams (0.013 mole) of 2,4,6-triamino-5-methylquinazoline (prepared in Example 13) and 25 mL of 2N hydrochloric acid (0.050 mole) was cooled to 5° C., and a solution of 1.1 grams (0.016 mole) of sodium nitrite in 4 mL of water was added dropwise. Upon completion of addition, the reaction mixture was stirred at 5° C. during a 10 minute period. In a separate reaction vessel, a stirred solution of 14.7 grams (0.225 mole) of potassium cyanide in 70 mL of water was cooled to 5° C., and a solution of 1.4 grams (0.056 mole) of copper(II) sulfate pentahydrate in 100 mL of water was added dropwise. To this solution was added, portionwise, the reaction mixture containing the quinazoline diazonium salt prepared above. Upon completion of addition, the reaction mixture was allowed to warm to ambient temperature as it stirred during a 2 hour period. After this time, the reaction mixture was diluted with 60 mL of aqueous 50% potassium carbonate and was extracted with four 700 mL portions of tetrahydrofuran. The combined extracts were acidified with 50 mL of acetic acid, and the mixture was concentrated under reduced pressure to a residual solid. The solid was subjected twice to column chromatography on silica gel. Elution was accomplished in each case with 20% N,N-dimethylformamide in ethyl acetate. The product-containing fractions were combined and concentrated under reduced pressure, yielding 1.1 grams of 2,4-diamino-6-cyano-5-methylquinazoline. The NMR spectrum was consistent with the proposed structure; however, it showed that the product was in the form of the acetate salt.

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