The invention relates to a dyeing composition for keratinous fibres containing, in a cosmetically acceptable solvent medium, at least one para-type oxidation dye precursor in combination with at least one heterocyclic coupler of formula: ##STR1## in which R denotes a hydrogen atom, a C.sub.1 -C.sub.4 radical, a C.sub.2 -C.sub.4 hydroxyalkyl radical, a C.sub.3 to C.sub.6 polyhydroxyalkyl radical, or a C.sub.2 -C.sub.6 alkoxyalkyl radical, Z, independently of R, denotes a C.sub.1 to C.sub.4 alkyl radical, a C.sub.2 to C.sub.4 hydroxyalkyl radical, a C.sub.3 to C.sub.6 polyhydroxyalkyl radical, a C.sub.2 -C.sub.6 alkoxyalkyl radical or a trifluoroethyl radical, R.sub.1 and R.sub.2 independently of each other denote a hydrogen atom or a C.sub.1 to C.sub.4 alkyl radical, or one of the addition salts of the compound of formula (I) with an inorganic acid, a process for the oxidation dyeing of hair using this composition as well as the new couplers of formula (I) where Z is other than methyl when R.sub.1, R.sub.2 and R=H, the process for their preparation, the new intermediate compounds of formula: ##STR2## and the process for their preparation.