Abstract: A process for the preparation of a compound of formula (I): wherein Ar represents an optionally substituted aromatic carbocycle or heterocycle, and R1 and R2 independently represent hydrogen, C1-10alkyl, C(O)C1-10alkyl or optionally substituted aryl provided that R1 and R2 are not both hydrogen which process comprises reacting together a compound of formula (II): Ar—X??(II) wherein Ar is as defined in relation to formula (I) and X represents a leaving group with a a compound of formula (III) wherein R1 and R2 are as defined in relation to formula (I) under aqueous conditions in the presence of a Pd (II) salt, a ligand and a Group I or Group II metal hydroxide base at a pH greater than 7. Compounds of formula (I) may be hydrolysed to the corresponding hydrazine.