The acylation of 2-aminoquinazol-4-one by unsaturated acid chlorides proceeds principally at the exocyclic nitrogen atom and is complicated in the case of acryloyl chloride by a further intramolecular condensation forming 1,2,3,4tetrahydropyrimido(2,l-b)quinazolin-2,6-dione.
A lower acylation temperature using methacryloyl chloride leads to accumulation of l-methacryloyl-2-aminoquinazol-4-one in the reaction mixture.
2-Aminoquinazol-4-ones on alkylation and acylation can show a capacity for dual reactions. Alkylation of 2-aminoquinazol-4-ones by unsaturated acids proceeds at the ring N s atom [I]. The alkylation products are unstable and undergo intramolecular acylation forming 1,2,3,4-tetrahydropyrimido(2,l-b)quinazolin-2,6-diones.
The aim of the present work is to investigate the acylation of 2-aminoquinazolin-4-one (I) by unsaturated acid chlorides. Alkylation of compound (I) by methacrylic (Ila), crotonic (IIb), and cinnamic (IIc) acid chlorides in the presence of an equimolar quantity of triethylamine in DM_F at 80-900C proceeds selectively at the exocyclic nitrogen atom with formation of 2-acylaminoquinazol~ (IIIa-c).