Propane, rhodium complexes

Propane, (J )-1,2-bis(diphenylphosphino)-rhodium complexes asymmetric hydrogenation, 6, 251... 

Chlorobis[l,3-bis(diphenylpho phine)propane]rhodium, Rh(dppp),Cl (1). The complex is prepared by heating COClRh P(Cf,Hs),], with the phosphine in xylene. ... 

CjHhO.i, Butanoic acid, 3-oxo-, methyl ester, rhodium complex, 27 292 QH,N, Propane, 2-isocyant-2-melhyl-, ruthenium complex, 26 275 C,H,P, Phosphine, (2,2-dimethylpropyli-dyne)-, 27 249, 251... 

C4,Hj,P, Phosphine, 2- (diphenylphos-phino)methyl]-2-methyl-l, 3-propane-diyl]bis(diphenyl-, rhodium complex, 27 287... 

Rhodium complexes of the ligand a,a-TREDIP (2) give very high iso regioselectivity in the hydroformylation of styrene under mild conditions, and this has been extended to the synthesis of 2 -(2-methoxy-6-naphthyl)propanal (3), a precursor of the antiinflammatory drug naproxen." ... 

Rhodium complexes with pyrazole or pyrazolate-type ligands have been studied as catalysts for hydrogenation of alkenes under ambient conditions in propan-2-ol <87JMOC34l). Hydroquinones... 

We have therefore proposed the following mechanism (Scheme If) propiophenone approaches the hydride rhodium complex (described by Gladiali [4]) facing its Si or Re side. This leads to two different complexes and gives (R) or (S) phenyl propan-l-ol. The shape and electronic features of the cavity where the rhodium complex is, should influence the activation energy of these intermediates, thus promoting one of them to react much faster than the other(the one that is created by the Si side approach). (R)-l-phenylpropanol synthesis is favoured. 

Kollar et al. prepared diastereomers of diphosphites which were synthesized by combining different modifications in the bridge and the phosphorus substituents [27, 28] 1. These ligands lead to active rhodium systems, and are considerably affected by chiral cooperativity. Some of these diastereomers prepared from (2S,4S) 2,4-pentenediol and (1 S,3S) diphenyl propane 1,3-diol form rhodium complexes in which the ligand is coordinated in an eight-membered ring, 14, 15, but the enantioselectivity obtained in the experiments described are no higher than 24% [27],... 

NHC derivatives of Wilkinson s catalyst 47 succumbed to displacement of the carbene by bidentate phosphines such as l,2-bis(diphenylphosphino)ethane (dppe), albeit under forcing conditions (Scheme 3.17). A related bidentate carbene/pyridine rhodium complex also underwent quantitative ligand displacement when treated with dppe or l,3-bis(diphenylphosphino)propane (dppp) at room temperature. ... 

A NHC-rhodium complex displayed an intriguing reactivity towards cyclobutanone derivatives. With complex 25, a cyclobutanone having an additional aldehyde function underwent chemoselective decarbonylation of the ketone moiety whilst the aldehyde carbonyl group remained intact, giving the corresponding cyclopropane in 82% yield (Scheme 8.7). On the other hand, no chemoselectivity was observed using [Rh(COD)Cl]2/dppp (dppp=l,3-bis(diphenylphosphino)propane), and both aldehyde and ketone units were decarbonylated to afford l-isopropenyl-4-propoxymethylbenzene in 84% yield. The use of the NHC ligand therefore provides a rare example of preferential activation of a C-C bond over a C-H bond. 

Preformed rhodium complexes or in situ systems with asymmetrical cyclic phosphite (23-26) and phosphinite (27) ligands bearing either trifluoromethyl or pentafluorophe-nyl group(s) were tested in the hydroformylation of styrene. Both systems were found to provide excellent hydroformylation activities at 100 °C. High regioselectivities toward the branched aldehyde (2-phenyl-propanal) were achieved at 40°C [51]... 

The preparation of chiral compounds by catalytic asymmetric hydrogenation is now well established. This year has again seen several reports on both the synthesis of and mechanistic studies on such systems, optical yields of 90% being achieved with a variety of catalysts. One such system which is worthy of note is the rhodium complex of the extremely simple chiral ligand (i )-l,2-bis(diphenyl-phosphino)propane [(i )-prophos] (7). This system is an efficient hydro-... 

X-ray structure analyses of Rh(COCH3)(I)2(dppp) (14) and [Rh(I I)(I)(//-I)(dppp)]2 (15), where dppp l,3-bis(diphenylphosphino) propane, were reported. Unsaturated complex (14) possesses a distorted five-coordinate geometry that is intermediate between sbp and tbp structures.69 Under CO pressure, the rhodium/ionic-iodide system catalyzes either the reductive carbonylation of methyl formate into acetaldehyde or its homologation into methyl acetate. By using labeled methyl formate (H13C02CH3) it was shown that the carbonyl group of acetaldehyde or methyl acetate does not result from that of methyl formate.70... 

Water-soluble complexes constitute an important class of rhodium catalysts as they permit hydrogenation using either molecular hydrogen or transfer hydrogenation with formic acid or propan-2-ol. The advantages of these catalysts are that they combine high reactivity and selectivity with an ability to perform the reactions in a biphasic system. This allows the product to be kept separate from the catalyst and allows for an ease of work-up and cost-effective catalyst recycling. The water-soluble Rh-TPPTS catalysts can easily be prepared in situ from the reaction of [RhCl(COD)]2 with the sulfonated phosphine (Fig. 15.4) in water [17]. 

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