The present invention provides a process for preparing a polyaromatic compound comprising at least one sequence of two aromatic rings. The process of the invention, which consists in reacting an aromatic compound bearing a leaving group and an arylboronic acid and/or its derivatives in the presence of a base and an effective amount of a nickel catalyst, is characterized in that the reaction is conducted in a reaction solvent which is water optionally in a mixture with an organic solvent and in the presence of an effective amount of a catalyst based on nickel with at least one water-soluble phosphine ligand.