3,5-Dichlorophenol → 2,4-Di[(1,1-dimethylethyl)carbonylamino]-6-phenoxyimino-5,6,7,8-tetrahydroquinazoline

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Reaction Steps

When the bridging group n is =NO--, 2,4-diamino-5,6,7,8-tetrahydroquinazoline 6-ethylene ketal is prepared from 1,4-cyclohexanedione mono-ethylene ketal and cyanoguanidine, as previously described. The 2,4-diamino moieties are then protected by the reaction of 2,4-diamino-5,6,7,8-tetrahydroquinazoline 6-ethylene ketal with pivalic anhydride in the presence of 4-dimethylaminopyridine, yielding 2,4-di[(1,1-dimethylethyl)carbonylamino]-5,6,7,8-tetrahydroquinazoline 6-ethylene ketal. The 6-ethylene ketal functional group is then cleaved from the so-prepared molecule with acetic acid and water, affording the corresponding 2,4-di[(1,1-dimethylethyl)carbonylamino]-5,6,7,8-tetrahydro-6-quinazolinone. A second intermediate, an O-(phenyl)hydroxylamine, is prepared by the reaction of an appropriately substituted or unsubstituted phenol, for example, 3,5-dichlorophenol, with O-(2,4-dinitrophenyl)hydroxylamine [prepared by the method of T. Sheradsky et al (Tetrahedron, 28, 3833 (1972)). The so-prepared O-(phenyl)hydroxylamine, for example, O-(3,5-dichlorophenyl)hydroxylamine, is then reacted with the 2,4-di[(1,1-dimethylethyl)carbonylamino]-5,6,7,8-tetrahydro-6-quinazolinone in ethanol, yielding the corresponding 2,4-di[(1,1-dimethylethyl)carbonylamino]-6-phenoxyimino-5,6,7,8-tetrahydroquinazoline. Treatment of the 2,4-di[(1,1-dimethylethyl)carbonylamino]-6-phenoxyimino-5,6,7,8-tetrahydroquinazoline with methanolic hydrochloric acid yields the targeted 2,4-diamino-6-phenoxyimino-5,6,7,8-tetrahydroquinazoline. Example 12 provides a detailed description of how this reaction is conducted.

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