Hydroformylation aryl phosphines

Second generation BINAPHOS-type ligands have been developed recently. Placing 3-methoxy substituents on the aryl phosphine unit furnishes a catalyst which allows for an enantioselective hydroformylation of vinylfurans (Scheme 19) [68]. 

Figure 7. The perfluoroalkyl-substituted aryl phosphines/phosphite prepared for the hydroformylation in SCCO2...

Erkey studied the hydroformylation of 1 -octene in scCOi using several different fluoralkyl and fluoralkoxy functionalized aryl phosphines [29]. They found an increasing activity of the rhodium catalyst with decreasing basicity ofthe phosphine ([3,5-(CF3)jC sHs] 3P > [4-CF3QH4]3P and [3-CFj QH4]3P > [4-CF30CgH4]3P). The basicity was measured by the carbonyl stretching frequencies ofthe complexes. 

Scheme 2.27 Methods for sulfonation of aryl phosphines and a selection of sul-fonated aryl mono- and diphosphines tested for rhodium-catalyzed aqueous two-phase hydroformylation.

In the mid-1960s, Wilkinson revealed that aryl phosphines are suitable for Rh-catalyzed hydroformylation. Subsequently, research mainly focused on metal rhodium [5]. As a result, the replacement of rhodium-phosphine complex catalytic process by Co-based process pushed the science and technology of olefin hydroformylation rapidly forward. The homogeneous catalytic process of UCC (Union Carbide Corporation, now Dow Chemical) is often referred to as the LPO (low-pressure 0X0) process. The reaction conditions then become easy. The conversion rate of olefin and the selectivity of aldehyde increase greatly. 

Cationic phosphine ligands containing guanidiniumphenyl moieties were originally developed in order to make use of their pronounced solubility in water [72, 73]. They were shown to form active catalytic systems in Pd-mediated C-C coupling reactions between aryl iodides and alkynes (Castro-Stephens-Sonogashira reaction) [72, 74] and Rh-catalyzed hydroformylation of olefins in aqueous two-phase systems [75]. 

Modified cobalt complexes of the type frans-Co2(CO)6(phosphine)2 are promising candidates for certain transition metal-catalyzed reactions, in particular for the hydroformylation of long-chained olefins [117]. A series of complexes Co2(CO)6[P(alkyl) (aryl)m]2 (n 0,1,2,3 m S - n) was synthesized and used for solubility measurements. Since the basicity of phosphines affects the catalytic activity, use of fluorous substituents might induce unexpected changes in the activity. Therefore, also derivatives with an additional ethyl spacer between the fluorous group and the phosphine moiety were examined (Sect. 3.1). 

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