1,4,9‐Benzo[b]triazaphenoxazine, the first and parent compound of this new heterocyclic ring, as well as its derivatives were prepared essentially by cyclo‐condensation of 2‐amino‐3‐hydroxypyridine with the appropriate 2,3‐dichloroquinoxaline in the presence of alkaline DMF or DMAC. Nitration of the product with mixed nitric and sulfuric acids gave the corresponding 13‐nitro derivative. Structural assignments were made by chemical evidence and by a study of the ultraviolet, infrared, nmr and mass spectra.
1,4,9‐Benzo[b]triazaphenoxazine, the first and parent compound of this new heterocyclic ring, as well as its derivatives were prepared essentially by cyclo‐condensation of 2‐amino‐3‐hydroxypyridine with the appropriate 2,3‐dichloroquinoxaline in the presence of alkaline DMF or DMAC. Nitration of the product with mixed nitric and sulfuric acids gave the corresponding 13‐nitro derivative. Structural assignments were made by chemical evidence and by a study of the ultraviolet, infrared, nmr and mass spectra.
3‐Methyl (3a) and 3‐t‐butyl‐1,4‐2H‐benzoxazine (3b) were synthesized by cyclization of the appropriate acetamidoketone (Scheme 1). The former is a highly unstable molecule which rapidly converts in an intractable mixture, while the latter slowly undergoes aerial oxidation affording the hemiacetal 4. The 4H‐forms of the same 3‐methyl (6a) and of the parent 1,4‐benzoxazine (9) could be obtained as 4‐acetyl derivatives. This latter, by hydrolysis, gave the cyclic trimer 10.
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