2-Amino-3-chloro-1,4-naphthoquinone → 2-(2-Chlorophenyl)naphth[2,3-d]oxazole-4,9-dione

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Reaction Steps

To a solution of 5 g (24 mmol) of 2-amino-3-chloro-1,4-dihydro-1,4-dioxonaphthalene in 60 mL of dioxane, 15.3 mL (120 mmol) of 2-chlorobenzoic acid chloride are added; after 5 min of stirring, 0.5 mL of concentrated sulfuric is added. The reaction mixture is heated to reflux for 4 h, and the precipitate obtained after evaporation of the dioxane at a reduced pressure is dissolved in 200 mL of dichloromethane. To this solution, 100 mL of a cold 10N sodium hydroxide solution are added. The mixture is stirred for 2 h. The organic phase is then extracted, washed several times with water and dried over calcium chloride. The solid residue obtained after evaporation of the solvent is purified on a medium-pressure column (support: silica; eluant: dichloromethane/heptane, 40/60). The product obtained is recrystallized after color removal in a heptane/dichloromethane mixture (1/1) to produce 5 g of 2-(2-chlorophenyl)-4,9-dihydro-4,9-dioxo-naphtho[2,3-d]oxazole in the form of light yellow crystals.

Provenance & Evidence