Central nervous system active compounds. XIV. On the cyclization of N-Acyl-N'-arylureas

Abstract

The cyclization of N-acyl-N'-arylureas in polyphosphoric acid has been reinvestigated. The product is not only the 4-substituted quinazolin-2(1H)-one as reported, but also contains the 2-acylaniline in major proportions. Two minor products have also been isolated. At 80�, an intermediate has been detected, the properties of which are consistent with it being the corresponding 2-acylphenyl- urea. Acyl ureas with strongly electron-withdrawing acyl groups form major amounts of the corresponding anilide by the formal loss of cyanic acid. The application of this reaction to the synthesis of quinazolinylphthalides has been investigated.