In a process for the preparation of ring compounds via a combinatorial synthesis, the reaction procedure is based on a Suzuki coupling, subsequent halo-demetallation and finally a further Suzuki coupling. The \u03b1-Al2O3 layer of the present invention is formed on a bonding layer of with increasing aluminium content towards the outer surface. The first side wall has a transverse cross sectional area of a first predetermined shape and the second side wall has a transverse cross sectional area of a second predetermined shape, the second predetermined shape being different from the first predetermined shape. The cross car beam is provided, between the driver’s side and the assistant driver’s side, with an opening in communication with an air conditioning unit.