A series of I-alkyl and 3-alkyl-2-benzoylamino-4-oxo-quinazolines has been prepared and found to have activity in tests for cognition enhancement in rats and mice.In the course of a project aimed at the synthesis of dibenzoylguanidines, 1. as cognition enhancing agents1 we wished to synthesize the N-methyl compound 2. One of the synthetic routesR = H, R' = p-CONH2 2, R = CH3, R' = o-CONH2that we pursued was the reaction of benzoyl isothiocyanate with 2-(methylamino)benzamide to provide the expected benzoylthiourea 3. In our reaction scheme we anticipated that treatment of 3 with hydrogen peroxide/ammonia (Method A)2*3 would yield the guanidine derivative, 4, followed by reaction with benzoyl chloride to yield the desired product, 5. However, compound 4 apparently was not formed. A high melting (252-253" C) crystalline solid was obtained instead. Spectral and elemental analyses demonstrated that it was N-benzoyl aminoquinazolinone 6a. Thesix-membered ring of 6 had formed via the displacement of the sulfinic or sulfonic acid of 3 by the amide nitrogen.4 Although benzoylaminoquinazolinones, e.g. 6b are reported in the literature.5 there are no examples of N-alkyl derivatives. The biological activity of compound 6 a in a Hypoxic Survival screen prompted further analog synthesis.