Add time:09/27/2019         Source:infona.pl

Condensation of 2-substituted-1,4-dihydroxyanthraquinones with 2-amino-benzenethiol generally results in the elimination of the 2-substituent and formation of 7-hydroxy-14H-naphtho[2,3-a]phenothiazine-8,13-dione (I). In addition to the anticipated replacement of labile 2-substituents such as halogeno, sulphone, carboxamido and t-amino, the elimination of ether, thioether, 1° and 2°-amino and hydroxy groups also occurs. 2-Alkyl substituents are retained, affording the 6-alkyl derivatives (II). 1,4-Dihydroxyanthraquinone undergoes direct thiolation and ring closure to I and similar reaction of 1-hydroxy-4-amino- and 1-hydroxy-4-arylamino-anthraquinones also gives I, with preferential reaction ortho to the amino group. The use of 1-hydroxy(or amino)-2-bromo-4-aminated anthraquinones, however, yields 7-aminated analogues (III). With both the 2- and 3-bromo-derivatives of 1-hydroxy-4-aminoanthraquinone, the reaction proceeds via debromination and subsequent reaction as with 1-hydroxy-4-aminoanthraquinone, giving I. The isomeric 6-hydroxy-14H-naphtho[2,3-a] phenothiazine-8,13-dione was obtained via 1,3-dihydroxyanthraquinone.

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