Nitrite → Nitroso acetamidophenol

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Reaction Steps

According to this scheme 1a, the compounds of formula (Ia) are prepared by reaction of an appropriate 3-acetamidophenol compound (1) with a nitrite (2), such as a sodium nitrite (X=Na), a potassium nitrite (X=K), etc., at a temperature of −3° C. The nitroso acetamidophenol (3) thus obtained is subsequently reacted with 1,3-dihydroxynaphthalene (4) in a solvent such as butanol, by heating to a temperature of approximately 70° C., then adding concentrated sulfuric acid and continuing the heating to 90° C., and then cooling, so as to form the appropriate 9-acetamido-benzo[a]phenoxazin-5-one. The latter compound is subsequently hydrolyzed by heating with moderately concentrated sulfuric acid so as to give the 9-amino-benzo[a]phenoxazin-5-one (5). The last step is equivalent to that of scheme 1.

Provenance & Evidence