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.