a compound having the formula : ## str1 ## where x is hydrogen , chlorine or bromine , b is hydrogen , methyl , ethyl or propyl , and one of the radicals r 1 or r 2 is phenyl which is unsubtituted or mono - or poly - substituted by chlorine , methyl , ethyl , t - butyl , phenoxy , methoxy , ethoxy , propoxy or butoxy , and the other is c 2 - c 8 - alkyl which is unsubstituted or substituted by c 1 - c 8 - alkoxy or phenyl , or is allyl , cyclopentyl , cyclohexyl , methylcyclohexyl , ## str2 ## the compounds of formula are used as dyes , preferably for cellulose and cellulose - containing fabrics .