Abstract: A method of preparing a compound useful as a brightener in aqueous copper electroplating solutions comprising reacting a compound of the following formula: ##STR1## with a compound of the formula:HS--R.sub.2 --Z.sub.nwherein:R.sub.1 and R.sub.2 are each an alkylene containing from 2 to 8 carbon atoms, an arylene, an alkylarylene, an arylalkylene or a heterocyclic group containing at least one nitrogen atom in its ring structure:x, y and z each is a hydrogen or a water-solubilizing group; andn is an integer of from 1 to 4; with the proviso that:when R.sub.1 is a heterocyclic group, x, y and z are hydrogen and R.sub.2 is an alkylene containing from 2 to 8 carbon atoms, an arylene, an alkylarylene or an arylalkylene;when R.sub.2 is a heterocyclic group, x, y and z are hydrogen and R.sub.1 is an alkylene containing from 2 to 8 carbon atoms, an arylene, an alkylarylene or an arylalkylene;when x or y is a water-solubilizing group, R.sub.

Abstract: A method of preparing a compound useful as a brightener in aqueous copper electroplating solutions comprising reacting a compound of the following formula: ##STR1## with a compound of the formula:HS--R.sub.2 --Z.sub.nwherein:R.sub.1 and R.sub.2 each is an alkyl containing from 2 to 8 carbon atoms, an aryl, an alkylaryl, an arylalkyl or a heterocyclic group containing at least one nitrogen atom in its ring;X, Y and Z each is hydrogen or a water-solubilizing group; andn is an integer of from 1 to 4; provided that:when R.sub.1 is a heterocyclic group, X, Y and Z are hydrogen and R.sub.2 is an alkyl containing from 2 to 8 carbon atoms, an aryl, an alkylaryl or an arylalkyl;when R.sub.2 is a heterocyclic group, X, Y and Z are hydrogen and R.sub.1 is an alkyl containing from 2 to 8 carbon atoms, an aryl, an alkylaryl or an arylalkyl;when X or Y is a water-solubilizing group, R.sub.