Various approaches to transfers improvement during biphasic catalytic hydroformylation of heavy alkenes

Abstract

The [HRh(CO)(TPPTS) 3] precursor, where TPPTS is the water-soluble P( m-C 6H 4SO 3Na) 3 ligand, has opened a large area for the Supported-Aqueous-Phase (SAP) catalysed functionalisation of heavy substrates. We investigated several ways to increase the efficiency of heavy alkenes hydroformylation by [Rh 2(μ-S tBu) 2(CO) 2(TPPTS) 2]. Addition of a cosolvent was shown to lead to a significant leaching of rhodium in the organic phase. Promising results were obtained. First, the Delmas–Chaudhari method of adding small amounts of PPh 3 to [HRh(CO)(TPPTS) 3] to maintain the complex at the interface, was examined for [Rh 2(μ-S tBu) 2(CO) 2(TPPTS) 2]. Here [Rh 2(μ-S tBu) 2(CO) 2(PPh 3) 2] was rapidly formed and is operating classically in the organic phase. Moreover, β-cyclodextrin was used as a phase-transfer agent allowing the inclusion of the substrate and its transport to the aqueous phase where the reaction is occurring. Finally, the use of silica with various hydration ratios in SAP catalysis led us to propose that the microreactors containing water, complex and extra TPPTS operate on the surface of the support.