Synthesis of some new styryl oxazolophenoxazines

Reductive acetylation of 3‐aminophenoxaz‐2‐one (II) gave 3‐acetylamino‐2‐acetoxy‐phenoxazine (IV). Thermolysis of (IV) gave 2‐methyl‐5 H ‐oxazolo(4,5‐ b )phenoxazine (V). The styryl derivatives (VIII) were synthesised by condensation of (V) with aromatic aldehydes. Quaternisation of (V) was carried out giving (VII). Oxidation of (V) using SeO 2 gave 2‐formyl‐5 H ‐oxazolo(4,5‐ b )phenoxazine (VI). Fragmentation patterns of certain of the products under electron impact are suggested.