Some reactions of quinazoline-2,4(1H,3H)-diones

Quinazoline-2,4(1H,3H)-diones (III) have been prepared by modifications of known methods. 3-Phenylquinazoline-2,4(1H,3H)-diones gave, with either phosphorous pentachloride or phosphoryi chloride, 2-chloroquinazoline-4(3H)-ones (IVb), which reacted with various amines to give 2-amino-derivatives (IVc—i). 3-Phenylquinazoline-2,4(1H,3H)-diones reacted with arylmagnesium halides to give 1,2,3,4-tetrahydro-2,4-diarylquinazoline2,4-diols (VII) and with alkylmagnesium halides to give 4-alkylidene-3,4-dihydroquinazolin-2(1H)-ones (X). The reaction mechanism is discussed. The products from both methyl- and methoxyphenylmagnesium halides underwent dehydration to give 3,4-dihydro-4-methylenequinazolines (IX), and 3,4-dihydroquinazolin-4-ols (XI), respectively. Unsubstituted 1,2,3,4-tetrahydroquinazolines reacted with Grignard reagents to give 2,4-disubstituted quinazolines (VIIIa and b).