Palladium-catalyzed 1,3-butadiene telomerization with methanol. Improved catalyst performance using bis-o-methoxy substituted triarylphosphines

New, improved phosphine ligands for palladium-catalyzed butadiene telomerization with methanol have been discovered. Using high throughput experimentation and an Electrospray Ionization-Mass Spectrometry (ESI-MS) investigation of telomerization catalysts solutions, we have identified phosphines of the type P(C6H4-2-OMe)(2)(C6H5-n(X)(n)), where X is an electron-withdrawing group, as high selectivity, high activity phosphine ligands for butadiene telomerization with methanol to 1-methoxy-2,7-octadiene (MOD-1). These ligands were designed to mitigate anaerobic oxidation of phosphines by alkylation which was shown by Electrospray Ionization-Mass Spectrometry (ESI-MS) studies to correlate with catalyst death and palladium precipitation in working telomerization catalyst solutions. The best phosphine-promoted catalysts achieve selectivities to desired 1-methoxy-2,7-octadiene of 94% at high butadiene conversion, significantly improved over those achieved commercially by triphenylphosphine. (C) 2011 Elsevier B.V. All rights reserved.