Convenient preparation of <i>N</i>‐substituted 2‐amino‐4<i>H</i>‐3,l‐benzoxazin‐4‐ones and 3‐substituted 2,4(1<i>H</i>,3<i>H</i>)‐quinazolinediones

Abstract

Abstract Room temperature treatment of 2‐(3‐arylureido)benzoic acids ( 1 ) and methyl 2‐(3‐alkyl‐, or 3‐arylureido)‐ benzoates ( 2 ) with concentrated sulfuric acid leads to N ‐substituted 2‐amino‐4 H ‐3,l‐benzoxazin‐4‐ones ( 3 ) in generally very good yields. The isomeric 3‐substituted 2,4(1 H ,3 H )‐quinazolinediones ( 4 ) are conveniently made in high yield by the action of aqueous‐ethanolic sodium hydoxide on 2.