Azobenzene → 2-(2-hydroxy-5-methylphenyl)benztriazole N-oxide

Participants

Reaction Steps

Example 9 of U.S. Pat. No. 4,835,284 is duplicated. A mixture of methanol (60 ml), water (30 ml), 97% sodium hydroxide (12.4 g), and 2-nitro-2'-hydroxy-5'-methyl azobenzene (12.9 g) is heated and stirred at 45°-50° C. 9-Fluorenone (1.0 g) and then glucose (5.5 g) are added to the resultant mixture over 30 minutes while stirring. The mixture is further stirred at 75° C. (boiling point) for 7 hours. As a result, the azobenzene disappears to produce 2-(2'-hydroxy-5'-methylphenyl)benzotriazole-N-oxide. Glucose (6 g) is then added to the reaction liquor over 30 minutes and the reaction is conducted 75° C. (boiling point) for further 6 hours. As a result, the above prepared N-oxide disappears. Thereafter, water (50 ml) is added to the reaction liquor, and the resultant reaction liquor is neutralized with 62% sulfuric acid (15 g) to precipitate a crystal. The precipitated crystal is separated by filtration, and the separated crystal is fully washed with water and further with methanol. The washed crystal is then dried, thus obtaining 9.6 g of 2-(2'-hydroxy-5'-methylphenyl)benzotriazole having a melting point of 128° to 130° C. at the yield of 85.0%. One can see that the reaction using the aromatic ketone 9-fluorenone takes over 14 hours to complete.

Provenance & Evidence