Synthesis and fluorescence properties of novel benzo[ a ]phenoxazin‐5‐one derivatives

Thirteen, benzo[ a ]phenoxazin‐5‐one derivatives 3a‐m were synthesized from 4‐nitrosoaniline hydrochlorides 1a‐m and ethyl 1,3‐dihydroxynaphthoate 2 and their fluorescence properties were discussed in terms of the electronic effect of substituents. A coupling reaction was carried out with 6‐carbethoxy‐9‐ N ‐(2‐hydroxyethyl)‐ N ‐methylamino‐5 H ‐benzo[ a ]phenoxazin‐5‐one (3k) and acetyl‐DL‐alanine to afford N ‐[(6‐carbethoxy‐5‐oxo‐5 H ‐benzo[ a ]phenoxazin)‐9‐yl]‐ N ‐methylaminoethylene acetyl‐DL‐alanine ester (4).