Synthesis, complexation behavior and application of a new diphosphite ligand in rhodium-catalyzed hydroformylation

Oxidative coupling of 3-(3-tert-butyl-4-hydroxyphenyl)propionic acid methyl ester (2) gave dimethyl 3,3′-(5,5′-di-tert-butyl-6,6′-dihydroxybiphenyl-3,3′-diyl)-dipropionate (1c), which upon phosphorylation/transesterification with a phosphochloridite derived from (R)-binaphthol, formed the new unsymmetrical binaphthol-bridged diphosphite 4. A rhodium catalyst based on 4 as ligand gave predominantly iso-selectivity in the hydroformylation of selected styrenes but opposite regioselectivity with 2,6-disubstituted derivatives. New chelate metal complexes (acac)RhL, PdCl2L and PtCl2L have been synthesized by reacting 4 with (acac)Rh(CO)2, PdCl2(MeCN)2 and PtCl2(COD), respectively. The structure of obtained compounds is determined based on 1H, 13C, 31P and 195Pt NMR spectroscopy and mass spectrometry data.

A new unsymmetrical diphosphite was synthesized. Its complexation behavior with Rh, Pd and Pt was investigated. A relevant Rh-complex was successfully used for the hydroformylation of styrenes.Figure optionsDownload as PowerPoint slideHighlights
► A new phosphorus ligand was prepared in a 2-step synthesis.
► As starting material serves a commercial ester group functionalized phenol.
► A rarely observed transesterification takes place.
► The new ligand forms an active hydroformylation catalyst with rhodium.