The hydroformylation of butyl acrylate in toluene was studied. Ligands were found to impact significantly on the reaction rates and selectivities. When combined with rhodium, ligands with large bite angles displayed higher activities. Whilst 1,4-bis(diphenylphosphino)butane (dppb) was found to be a best choice, a modified, electron-deficient dppb ligand led to considerably higher catalytic activities in comparison with the electron-rich analogues. Other parameters were also examined, including ligand/rhodium ratios, and concentrations of the catalyst and olefin. (c) 2008 Elsevier B.V. All rights reserved.