Rhodium-phosphine complexes, reaction

Dialdehydes 8 have been converted to y-lactones 9 in the presence of a rhodium phosphine complex as catalyst. The example shown below demonstrates that this reaction works also with aldehydes that contain a-hydrogen atoms. 

Hydroaminomethylation of alkenes occurred to give both n- and /. so aliphatic amines catalyzed by [Rh(cod)Cl]2 and [Ir(cod)Cl]2 with TPPTS in aqueous NH3 with CO/H2 in an autoclave. The ratio of n-and /.soprimary amines ranged from 96 4 to 84 16.178 The catalytic hydroaminomethylation of long-chain alkenes with dimethylamine can be catalyzed by a water-soluble rhodium-phosphine complex, RhCl(CO) (Tppts)2 [TPPTS P(m-C6H4S03Na)3], in an aqueous-organic two-phase system in the presence of the cationic surfactant cetyltrimethy-lammonium bromide (CTAB) (Eq. 3.43). The addition of the cationic surfactant CTAB accelerated the reaction due to the micelle effect.179... 

Oheme and co-workers investigated335 in an aqueous micellar system the asymmetric hydrogenation of a-amino acid precursors using optically active rhodium-phosphine complexes. Surfactants of different types significantly enhance both activity and enantioselectivity provided that the concentration of the surfactants is above the critical micelle concentration. The application of amphiphilized polymers and polymerized micelles as surfactants facilitates the phase separation after the reaction. Table 2 shows selected hydrogenation results with and without amphiphiles and with amphiphilized polymers for the reaction in Scheme 61.335... 

In 1997, Miyaura and co-workers reported the nonasymmetric version of 1,4-addition of aryl- and alkenylboronic acids to a,/ -unsaturated ketones using rhodium-phosphine complex as the catalyst.97 Later, Hayashi and Miyaura realized the asymmetric 1,4-addition with high catalytic activity and enantioselectivity.98 In the presence of ( y)-BINAP, the reaction of 2-cyclohexenone with 2.5 equiv. of phenylboronic acid gave (A)-3-phenylcyclohexanone with 97% ee (BINAP = 2,2 -bis (diphenylphosphino)-l,l -binaphthyl Scheme 29).99... 

Similarly, highly selective hydrogen reductions of rhodium-acyl intermediates are known, such as in hydroformylation reactions. Rhodium phosphine complexes are highly selective with little further reduction of products to alcohols (19). 

It has been reported that the chiral NMR shift reagent Eu(DPPM), represented by structure 19, catalyzes the Mukaiyama-type aldol condensation of a ketene silyl acetal with enantiose-lectivity of up to 48% ee (Scheme 8B1.13) [29-32]. The chiral alkoxyaluminum complex 20 [33] and the rhodium-phosphine complex 21 [34] under hydrogen atmosphere are also used in the asymmetric aldol reaction of ketene silyl acetals (Scheme 8BI. 14), although the catalyst TON is quite low for the former complex. 

Homogeneous hydrogenation in the fluorous phase has been so far reported only for a limited set of simple olefins (Richter et al., 1999, Rutherford et al., 1998), as exemplified with the neutral rhodium phosphine complex 18 as catalyst precursor (eq. 5.7). Isomerization of the substrate 1-dodecene (17a) was observed as a competing side reaction under the reaction conditions. The catalyst formed from 18 could be recycled using a typical FBS protocol, but deactivation under formation of metal deposits limited the catalyst lifetime. 

Butadiene and ethylene are codimerized with a soluble rhodium-phosphine complex as the catalyst. Very little has been reported on the mechanistic evidence for this reaction. However, a catalytic cycle as shown in Fig. 7.9 involving a rhodium hydride seems likely. Reducing rhodium trichloride with ethanol in the presence of a tertiary phosphine generates the hydride complex 7.32. The 1,4-hydride attack on the coordinated butadiene gives an rf-allyl complex. This is shown by the conversion of 7.33 to 7.34. Ethylene coordination to 7.34 produces 7.35. 

We previously prepared surface-bonded rhodium phosphine complexes in Al-MCM-41. In a solution of dichloromethane, [Rh(acac)(chiraphos)] and Al-MCM-41 react to a surface bonded [(Os)x-Rh(chiraphos)] complex due to an exchange reaction of the acetylacetonato ligand and surface oxygens of the acidic support12. Here we present a heterogeneous Rhodium diphosphine catalyst and its application in the enantioselective hydrogenation of dimethylitaconate. The results indicate the localisation of the complex inside of the mesoporous channel system. 

When our studies commenced it had been assumed that the mechanism of asymmetric hydrogenation by chelating rhodium phosphine complexes followed a similar pathway. It has been demonstrated, however, that the timing is quite different, and that oxidative addition of hydrogen to metal does not occur in the initial stages of reaction. This conclusion follows from studies on the phosphorus-31 NMR spectra of hydrogenated complex solutions made separately by Halpern,... 

The hydroformylation of propene to form butyralde-hyde invariably produces some isobutyraldehyde at the same time (reaction 1.21).216 One of the best processes uses a water-soluble rhodium phosphine complex to produce 94.5% of the former and 4.5% of the latter.217 The products form a separate layer that is separated from the water. Rhodium is expensive so it is important to lose as little as possible. In 10 years of operation by Rhone-Poulenc-Ruhrchemie 2 million metric tons of butyralde-hyde have been made with the loss of only 2 kg of rhodium. The process is 10% cheaper than the usual one. Higher olefins are not soluble enough in water to work well in the process. The process does work for omega-alkenecar-boxylic acids such as 10-undecenoic acid, where a 97 3... 

The asymmetric hydrogenahon of dehydro-a-amino acid derivahves catalyzed by chiral rhodium-phosphine complexes is a successful example of an aqueous micellar system [Eq. (1)]. Normally, achvity and selectivity are decreased by changing from an organic solvent to water but the addihon of a small amount of a micelleforming amphiphile leads to a significant increase in the reaction rate and in the enanhoselectivity [13, 14]. 

Hydrometallations of alkenes and acetylenes such as hydroboration, hydrosila-tion, hydroalumination, hydrostannation and hydrozirconation are useful synthetic reactions. Rhodium-phosphine complexes catalyze hydroboration of substituted styrenes with a catecolborane (Scheme 68). An extensive survey of the phosphine... 

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