A method of using homogenous rhodium catalysts comprising N-heterocyclic carbene ligands for the hydroformylation of olefins and substituted olefins is provided. In some aspects, the methods provided herein relate to the hydroformylation of allyl alcohol to 4-hydroxybutaldehyde in the presence of a rhodium catalyst which contains one or more N-heterocyclic carbene ligands of the formula: wherein R1, R2, R3, and R4 are defined herein.