Use of the nuclear Overhauser effect in the determination of the orientation of aromatic substitution in tricyclic quinoxalinones
Abstract
1 H N.m.r. nuclear Overhauser enhancement studies involving the amide NH of 7,8,9,10-tetrahydropyrido[1,2-a]quinoxalin-6-ones have been used to identify the aromatic proton signals of the quinoxalin-6-ones and to show that bromination with bromine in glacial acetic acid takes place at C-3 whilst nitration with potassium nitrate–concentrated sulphuric acid takes place at C-2.