| 摘要 |
This invention relates to phenazine dyes, and more particularly, to phenazine dyes suitable as intermediates for leuco phenazine dyes. Essentially all of the phenazine dyes capable of providing red, orange, and magenta hues have unsubstituted amine groups at the 3- or 7-position, or both. The presence of unsubstituted amine groups at the 3- or 7-positions, or both, does not allow one to employ a simple, direct method to reduce and acylate the dye at the 10-position without also acylating the dye at the 3- or 7-position or both. In a reduced leuco dye which contains acyl groups at the 10-position as well as the 3- and/or 7-positions, reoxidation under normal conditions removes only the acyl group at the 10-position, which will yield a dye form having different absorption properties from that of the original, unreduced dye containing the unsubstituted amine group. Therefore, phenazine dyes known in the art, such as phenosafranine, which are red, magenta, and the like, do not provide the original dye color upon reduction acylation and reoxidation. Although phenazine dyes containing substituents at the 3- and 7-positions are well known, essentially all of them provide turquoise or blue colors. This invention provides 3,7-diamino phenazine dyes having at least one electron-withdrawing substituent on at least one of the groups attached to the amine groups at the 3- and 7-positions, provided that the algebraic sum of the para position Hammett sigma ( sigma p) values for the groups attached to the nitrogen atoms of the amine groups at the 3- and 7-positions is more positive than about -0.6. The group containing the electron-withdrawing substituent can be selected from: (1) a substituted alkyl group, and (2) a substituted aryl group.
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