Synthesis of Leuco Quinones

Anthraquinone leuco dyes are widely known as vat dyes.10 Vat dyes possess extensively conjugated aromatic systems containing two or more carbonyl groups, e.g., anthraquinone, indigoid chromophores. The colored form of vat dyes are insoluble in water. The dyes are applied by a process whereby the dye is converted to the reduced form (leuco dye) which is soluble in water and can penetrate into a cellulosic fiber. On exposure to the atmosphere the leuco form is oxidized to the original quinoid form which then precipitates as an aggregate. Vat dyes generally have excellent chemical and photochemical stability. 

The leuco quinoneimine dyes are unstable to isolate but the substitution of an electron-withdrawing group such as acyl,13 carbamoyl,13 carboxy,13 or arylsulfonyl 12 group at the amino nitrogen atom stabilizes the 

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