Sulfuric Acid → 1-Anthracenediazonium, 9,10-dihydro-9,10-dioxo-, sulfate (1:1)

Participants

Reaction Steps

Briefly, 3,5-dibromo-6H-anthra[1,9-cd]isoxazol-6-one (1) was prepared by the diazotation of 1-amino-2,4-dibromoanthraquinone by adding sodium nitrite to a solution of the amine in concentrated sulfuric acid to give the 1-anthraquinonediazonium hydrogen sulfate which was subsequently converted to the 1-azidoanthraquinone by reacting with an aqueous solution of sodium azide. The azidoanthraquinone was azeotropically refluxed in toluene to provide, by evolution of nitrogen, the required isoxazole ring (1). Arylamination of 1 at the 5-position was accomplished with anhydrous AlCl3 in nitrobenzene at ambient temperature to give a moderate yield of the 6-arylamino substituted compound (2). A second amination was carried out at the 3-position using refluxing acetonitrile to give a moderate yield of (3). Next, hydrolysis of the benzoate ester (3) to the carboxylic acid (4) occurred under conditions of heating an aqueous solution of sodium hydroxide and methanol. The sodium carboxylate salt (5) was synthesized quantitatively by reacting (4) with sodium hydride in THF at room temperature.

Provenance & Evidence