Abstract: The invention provides a compound of formulaA--E--SO.sub.2 --NH--SO.sub.2 --E--A (I),whereineach --E--, independently, signifies a bivalent aromatic radical,each --A, independently, signifies a heterocyclic group of formula ##STR1## and the group --R.sub.1 --R.sub.2 -- signifies a 2- or 3-membered bridging chain to form, together with the group ##STR2## to which it is bound, a 5- or 6-membered heterocycle, with the proviso that the carbon indicated by the asterisk * is capable of being coupled with a diazonium compound,or a mixture of compounds of formula (I), and the use thereof as (bis)coupling components for the production of azodyes and metal complexes, which are useful as dyes, especially for the dyeing of leather.

Abstract: Azo dyestuffs of the formula ##STR1## wherein R.sub.1 denotes acyl,R.sub.2 denotes hydrogen, fluorine, chlorine or trifluoromethyl,R.sub.3 denotes hydrogen, optionally substituted C.sub.1 -C.sub.4 -alkyl, cyclohexyl or optionally substituted phenyl andR.sub.4 denotes hydrogen or C.sub.1 -C.sub.4 -alkyl groupare suitable for dyeing natural and synthetic fibre materials, for example for dyeing wool or polyamide fibres, in level read to violet shades with very good fastnesses to light, wet processing and perspiration, the color yield being good.