Highly regioselective hydroformylation of internal, functionalized olefins applying Pt/Sn complexes with large bite angle diphosphines

The regioselective hydroformylation of methyl 3-pentenoate (M3P) leading to linear 5-formyl methyl pentanoate (3-FMP) was studied. For this purpose Pt/Sn catalyst systems were modified by diphosphine ligands derived from heteroaromatic xanthene-type hydrocarbons. These xantphos ligands possess a large bite angle combined with a rigid backbone. The (PnP)PtCl2 catalyst precursor complexes were prepared and characterized by 1H- and 31P NMR-spectroscopy. The catalysts show unprecedented high regioselectivity to the terminal aldehyde. In addition, the undesired hydrogenation of the substrate and the products is largely suppressed. It was shown that activity as well as selectivity are controlled both by the bite angle and the rigidity of the backbone of the ligands.