A new class of oxazolidinone- and phthalimide-based oxidation dye couplers and their effect on azomethine dye color

In the study of the effects of auxochromes on azomethine dye color, an oxazolidinone ring in the acceptor portion of the dye was useful both as a masking group for preparation of the electron-donating hydroxyethyl group, and as an electron-withdrawing auxochrome. In the case of m-aminophenol derivatives coupled with p-phenylenediamine, there was a 15 nm bathochromic shift relative to the parent azomethine of the series (PPD-MAP)3 and a 30 nm bathochromic shift relative to the azomethine formed from PPD and AHT, which contains an electron-donating group. However, unlike many electron-withdrawing groups, the oxazolidinone group does not significantly slow the rate of oxidative coupling of the MAP derivative with the primary intermediate to form the azomethine dye; it was about 70% of that for PPD with AHT, making the oxazolidinone-containing MAP a potentially effective oxidation dye intermediate. The effect on color of an oxazolidinone moiety in the acceptor portion of an azomethine formed with a 4,5-diaminopyrazole as the primary intermediate was similar in the magnitude of the bathochromic shift. Finally, including an auxochrome (phthalimide) that is electron-withdrawing in the acceptor portion of the azomethine, but which has decreased overlap with the π-system of the chromophore due to twisting out of plane caused by steric interactions, results in a significant hypsochromic shift.