Rhodium-catalyzed hydroformylation enantioselective

Abstract Recent advances in synthetic aspects of the rhodium-catalyzed hydroformylation of alkenes are reviewed. Emphasis is given to practical improvements, efficient new catalysts for regioselective and enantioselective hydroformylation, and to applications of the reaction in organic synthesis. Furthermore, new developments in directed hydroformylation are covered as well as new approaches toward efficient hydroformylation catalysts employing the concept of self-assembly. 

Finally, water-soluble phosphorylated BlNAPs were tested as ligands in aqueous biphasic rhodium-catalyzed hydroformylation of vinyl acetate. Compared with catalysts prepared with the parent ligand in a homogeneous medium, the chemo-, regio- and enantioselectivities were markedly lower [24]. 

Electrophilic aldehydes have been also generated through a rhodium catalyzed hydroformylation process of alkenes, which has been combined with the aldol addition catalyzed by prohne (1,30 mol%) in a tandem reaction sequence, providing the aldol products 4 in good yields (59-86%) and enantioselectivities (71-83%), but with low diastereoselectivities [20]. 

The most common oxidatiou states and corresponding electronic configurations of rhodium are +1 which is usually square planar although some five coordinate complexes are known, and +3 (t7 ) which is usually octahedral. Dimeric rhodium carboxylates are +2 (t/) complexes. Compounds iu oxidatiou states —1 to +6 (t5 ) exist. Significant iudustrial appHcatious iuclude rhodium-catalyzed carbouylatiou of methanol to acetic acid and acetic anhydride, and hydroformylation of propene to -butyraldehyde. Enantioselective catalytic reduction has also been demonstrated. 

Rhodium complexes with chiral dithiolato and dithiother ligands have been studied in rhodium-catalyzed asymmetric hydroformylation. In all instances, enantioselectivities were low.391-393 Catalysis with compounds containing thiolate ligands has been reviewed.394... 

Fig. 6 Rhodium-catalyzed asymmetric hydroformylation of styrene using ligands 3 and 23-26. Enantioselectivities obtained at 100 bars of syngas and 60 °C are shown in brackets...

The potential of QUINAPHOS ligands for asymmetric catalysis was assessed in rhodium-catalyzed enantioselective hydroformylation using styrene as a benchmark substrate (Table 2.1.5.2). The catalysts were prepared in situ from [(acac)Rh(CO)2] and 4 equiv of the diastereomeric mixture or the single diaste-... 

I 7 Enantioselective Catalysis in Ionic Liquids and Supercritical CO Table 7.17 Rhodium-catalyzed asymmetric hydroformylation of styrene in SCCO2. 

Scheme 3.4 Synthesis ofthe chiral fluorous (R,S)-3-H F -Binaphos (16) ligand for the rhodium-catalyzed enantioselective hydroformylation of olefins in supercritical carbon dioxide (seCOj) [19] (Rf = (CH2)2(CF2)6F).

Homogeneous catalysts play an important role in industry as well as in research laboratories. Established applications include, for example, polymerization processes with zirconocene and its derivatives, rhodium- or cobalt-catalyzed hydroformylation of olefins, and enantioselective isomerization catalysts for the preparation of menthol. In contrast to heterogeneous catalysts, more experimental studies of reaction mechanisms are available and the active species can be characterized experimentally in some cases. Most catalysts are based on transition metal compounds, for which electronic structures and properties are well studied theoretically. A substantial number of elementary reactions, such as reductive elimination, oxidative addition, alkene or carbonyl migratory insertion, etc., have been experimentally Studied in detail by means of isotopic, NMR, and IR studie.s, as well as theoretically. ... 

Zhang XW, Coo BN, Yu SC, Zhang XM. Rhodium-catalyzed asymmetric hydroformylation of A-allylamides highly enantioselective approach to beta(2)-amino aldehydes. Angew. Chem. Int. Ed. 2010 49 4047 050. 

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