Synthesis of 2-aminochromones. Studies on the nucleophilic displacement of sulphinyl and sulphonyl groups in the 2-position of 5,8-dimethoxychromone

The synthesis is described of a number of N-substituted 2-amino-5,8-dimethoxychromones ( 1 ) by replacement of the sulphoxide group in 2-ethylsulphinyl-5,8-dimethoxychromone ( 5a ) with the appropriate amine. Analogous substitution of 2-ethylsulphonyl-5,8-dimethoxychromone ( 5b ) is also possible but limited by the instability of the sulphone. Replacement reactions of 5a involving oxygen, sulphur, and phosphorus nucleophiles are also described.