Hydroformylation of vinylarenes is pet-formed using rhodium precursors with various P,N-donor chiral 4-diphenylphosphanyl-1-(dialkylamino)butane ligands (8a-d) with DIOP backbone. The systems were active at mild conditions and the selectivity in aldehydes was total when mixtures of CO/H-2 at a ratio 1/1 were used. The maximum regioselectivity in the branched products was 95%. The highest ee was 23%. NMR studies under catalytic conditions showed that species with monodentate ligands were present in the catalytic solution. (C) 2002 Published by Elsevier Science B.V.