Abstract: A process for the preparation of aromatic compounds of the general formula I,Ar--X Iin which Ar represents an optionally substituted aryl group and X represents a group OH, Cl, Br or CN, by reaction of an aryl diazoniumsalt of the formula II,Ar--N.dbd.N.sup.+ Y.sup.- IIin which Ar is as defined above and Y represents a suitable counterion, with water, hydrogen chloride or a salt thereof, hydrogen bromide or a salt thereof, or a cyanide in the presence of a copper(I)salt, characterized in that the copper(I)salt is a copper(I)salt derived from an hydroxy carboxylic acid.

Abstract: Thioxanthone derivatives of the general formula I ##STR1## wherein R.sup.1 wherein R.sup.1 represents a halogen atom or a C.sub.1-10 alkoxy group, R.sup.2 and R.sup.4 each represent a hydrogen atom, a halogen atom or a C.sub.1 -C.sub.6 alkyl group, X represents oxygen or sulphur, and R.sup.3 represents a C.sub.1 -C.sub.10 alkyl group optionally substituted by a hydroxy group which hydroxy group may be alkylated by an optionally substituted C.sub.1-6 alkyl, C.sub.1-6 alkenyl or a benzyl group or acylated by a C.sub.1-8 alkanoyl or C.sub.1-8 alkenoyl group, a C.sub.1-10 alkenyl group, a C.sub.3 -C.sub.6 cycloalkyl group, a C.sub.1 -C.sub.8 alkanoyl group, a C.sub.1-8 alkenoyl group, an optionally substituted phenyl group, an optionally substituted benzyl group or an optionally substituted benzoyl group.