Disperse dyestuffs of the formula ##STR1## in which R, R.sub.1 and R.sub.2 denotes alkyl,E denotes A or B,A denotes alkyl, alkenyl, cycloalkyl or aralkyl,B denotes aryl,m denotes the numbers 2-4,Y and Z denotes R, Cl, Br or O--E andX denotes R, Cl, Br, CHO, CO--E, COO--A, CONR--E, SO.sub.2 --E, SO.sub.2 O--B,SO.sub.2 NR--E, CN, NO.sub.2, CF.sub.3 or Y--C.sub.6 H.sub.4 --N.dbd.N-- with the proviso that Y and Z represent H, Cl, Br or O--E if X denotes 4-nitro, are especially suitable for the dyeing of polyester material since they give deep dyeings with high fastness to sublimation and interesting greenish-tinged yellow shade on that material.