The compounds of the formula I ##STR1## where R is unsubstituted or substituted phenyl or naphthyl, R.sup.1 and R.sup.2 are each unsubstituted or substituted alkyl, alkenyl or cycloalkyl, and one of the radicals may furthermore be hydrogen, R.sup.3 is hydrogen, methyl, methoxy, ethoxy or chlorine, and R.sup.4 is acylamino, are particularly useful for dyeing polyesters.
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