Selective synthesis of 1-benzylquinazoline-2,4(1h,3h)-dione

The reaction of 1,3-dibenzoylquinazoline-2,4(1H,3H)-dione with potassium carbonate in anhydrous DMF at room temperature leads to the formation of a potassium salt of 3-benzoylquinazoline-2,4(1H,3H)-dione, the alkylation of which in situ with benzyl chloride produces 1-benzyl-3-benzoylquinazoline-2,4(1H,3H)-dione. A one-pot method for the preparation of N1-monosubstituted derivatives of quinazoline-2,4(1H,3H)-dione was developed. The effect of an alkaline agent on the yield and ratio of the debenzoylation products was studied.