The dyestufis may be used for dyeing various plastics and certain of the dyestuffs, particularly those in which R is hydroxyalkyl radical of 2 or 3 carbon atoms and R is a lower alkyl radical having from 1 to 5 carbon atoms, show excellent afiinity to cellulose acetate and may be used in dyeing cellulose parted to plastics and certain synthetic fibers by dyestuffs of the present invention are very