Synthesis and properties of some 7‐dimethylamino‐1,4‐benzoxazin‐2‐ones

The synthesis of the 7‐dimethylamino‐1,4‐benzoxazin‐2‐ones ( 5 ), fluorescent dyes, by condensing α‐keto‐acids with 2‐amino‐5‐dimethylaminophenol is described. When the 3‐substituent is a methyl group, these compounds can be further condensed with aromatic aldehydes to provide the styryl dyes ( 6 ). These products are easily opened by hydrochloric acid in ethanolic solution to afford the corresponding benzalketoacid ethyl esters ( 7 ).