Hydrogenations chlorotris rhodium

Chlorotris(triphenylphosphine)rhodium Homogeneous hydrogenation of carbon-carbon double bonds Preferential hydrogenation... 

Related Reagents. Trichlorosilane triethylsilane dimethyl-(3) phenylsilane chlorotris(triphenylphosphine)rhodium(T) hydrogen peroxide potassium fluoride tetrabutylammonium fluoride acetyl chloride aluminum chloride. 

Chlorotris(triphenylphosphine)rhodium Preferential hydrogenation of terminal carbon-carbon double bonds... 

Halpern J, Okamoto T and Zakhariev A 1976 Mechanism of the chlorotris(triphenylphosphine)rhodium(l)-catalyzed hydrogenation of alkenes J. Mol. Catal. 2 65-9... 

Aldehydes, both aliphatic and aromatic, can be decarbonylated by heating with chlorotris(triphenylphosphine)rhodium or other catalysts such as palladium. The compound RhCl(Ph3P)3 is often called Wilkinson s catalyst.In an older reaction, aliphatic (but not aromatic) aldehydes are decarbonylated by heating with di-tert-peroxide or other peroxides, usually in a solution containing a hydrogen donor, such as a thiol. The reaction has also been initiated with light, and thermally (without an initiator) by heating at 500°C. 

Acyl chlorides containing an a hydrogen are smoothly converted to alkenes, with loss of HCI and CO, on heating with chlorotris(triphenylphosphine)rhodium, with metallic platinum, or with certain other catalysts. The mechanism probably involves conversion of RCH2CH2COCI to RCH2CH2—RhCO(Ph3P)2Cl2 followed by a concerted syn elimination of Rh and H. See also 14-39 and 19-12. 

The diester 226 undergoes ring-closure to the methylenecyclopentane derivative 227 in the presence of a catalytic amount of chlorotris(triphenylphosphine)rhodium in boiling chloroform saturated with hydrogen chloride. In contrast, if the reaction is catalysed by palladium(II) acetate, the isomeric cyclopentene 228 is produced (equation 115)118. 

Tihe decarbonylation reaction utilizing chlorotris (triphenylphosphine)-- rhodium(I) is a potentially useful method for converting acid chlorides to olefins or alkyl chlorides. Acid chlorides which contain a f3 hydrogen produce olefins (Reaction 1) while an alkyl chloride is the product when no / hydrogen is present (J, 2, 3, 4, 5, 6) (Reaction 2). 

In an attempt to resolve this question of stereochemistry and also to determine whether or not the decarbonylation of an acid chloride containing a f3 hydrogen takes place stereospecifically, erythro- (XI) and fhreo-2,3-diphenylbutanoyl chlorides (XII), obtained by the reaction of the known acids (13, 14) with oxalyl chloride, were synthesized. The reaction of these acid chlorides (see Reaction 8) with chlorotris( triphenyl-phosphine) rhodium gave the corresponding acyl complexes of type lib [R = C6H5CH(CH3)CH(C6H5)]. Decarbonylation of the erythro- cy complex in benzene at 30 °C gave a 90% yield of frans-a-methylstilbene while decarbonylation of the threo-acyl complex under similar reaction... 

The water-soluble Wilkinson-type catalyst chlorotris(diphenylphosphinoben-zene-m-sulfonate)rhodium(I), RhQfdpm) (19), acts as catalyst for H2-evolution [158], hydrogenation and hydroformylation [159]. In a photosystem composed of Ru(bpy)i+ as photosensitizer, ascorbic acid, HA, as electron donor and RhCl(dpm)3, hydrogen evolution proceeds with a quantum efficiency corresponding to (p = 0.033. In the presence of ethylene or acetylene, hydrogen evolution is blocked and hydrogenation of the unsaturated organic substrates predominates. Table 6 summarizes the quantum yields for H2-evolution and... 

Some catalysts suffer a different type of alkyne poisoning. Chlorotris(triphenylphosphine)rhodium(I) is an effective terminal alkyne polymerization catalyst. When this complex is used in the reduction of these alkynes, it gradually loses its activity because of the competing polymerization reaction. Even initially the rate of alkyne hydrogenation is much slower than that of the corresponding alkene because of the greater binding constant of the former substrate. 

Catalytic hydroacylation. Aldimines of 3-methyl-2-aminopyridine and aromatic aldehydes react with chlorotris(triphenylphosphine)rhodium(I) (1) in THF at 55 to afford products of imine C—H insertion (3). Aminals of 2-aminopyridine and aldehydes with a-hydrogens (4) similarly react with 1 to give 5 presumably, the aminals are in equilibrium with the corresponding imines under these conditions. These complexes undergo hydroacylation reactions with ethylene as illustrated for 2. The overall reaction can be performed with catalytic quantities of 1, as indicated for the reaction of 4. 

Enantiomerically pure carboxylic acids are routinely obtained from N-acylsultams by Hydrogen Peroxide assisted saponification with Lithium Hydroxide in aqueous THF. 4 Alternatively, transesterification can be effected under neutral conditions in allyl alcohol containing Titanium Tetraisopropoxide, giving the corresponding allyl esters which can be isomerized/hydrolyzed with Wilkinson s catalyst (Chlorotris(triphenylphosphine)rhodium(I)) in Et0H-H20. This provides a convenient route to carboxylic acids containing base-sensitive functionality. Primary alcohols are obtained by treatment with L-Selectride (Lithium Tri-s-butylborohydride) in THF at ambient temperature. ... 

Chlorotris(triphenylphosphine)rhodium(I), [RhCl(PPh3)3], was reported independently by three groups in 1965, " and its application to catalytic homogeneous hydrogenation has been studied intensively by Wilkinson s group. The Wilkinson catalyst is now the most widely used for hydrogenation of a variety of unsaturated substrates, and several extensive reviews of this catalyst have been published. ... 

To investigate the oxidative addition of acyl halides to a metal to form the acyl complex and to find a better decarbonylation agent, we selected chlorotris(triphenylphosphine) rhodium (XI) as a model complex. This complex is known to catalyze the oxo reaction (8) and the homogeneous hydrogenation of acetylenes and olefins (7, 28). 

Chlorotris(triphenylphosphine)rhodium (Wilkinson s catalyst) is among the most efficient catalysts and permits hydrogenation in homogeneous solution. The Rh complex is readily prepared by heating rhodium chloride with excess triphenylphosphine in ethanol. 

Chlorotris(triphenyIphosphine)rhodium, [(C Hs)3P]3RhCI. Mol. wt. 913.09 This organometallic complex is obtained as purple-red crystals by interaction of ethanolic solutions of RhCla-SHsO and a sixfold molar excess of triphenyl-phosphine. It catalyzes exceedingly rapid hydrogenation of double and triple bonds. Aliphatic aldehydes are decarbonylated to the corresponding paraffins according to the equation ... 

Catalytic hydrogenation of benzo[f]quinoline over platinum in trifluoroacetic acid and subsequent treatment with acetic anhydride affords a mixture of 4-acetyl-l,2,3,4,7,8,9,10-octahydrobenzo[f]quinoline (57) m.p. 68-69°C, 7,8,9,10-tetrahydrobenzo[f]quinoline (58) m.p. 55-56°C, and 5,6,6a,7.8,9,10,10a-octahydrobenzo[f]quinoline (59) m.p. 146-147°C. These three compounds can be separated (M. Cardellini et al., J. org. Chem., 1982, 47, 688). Selective reduction of the heterocyclic ring occurs under mild conditions using l drogen in the presence of chlorotris(triphenylphosphine) rhodium (I) (Ph2P)2RhCl (R.H. Fish, J.L. Tan and A.D. Thormodsen, J. org. Chem., 1984, 4500). 

Reduction of the heterocyclic ring of the benzo[h]quinoline occurs selectively using chlorotris(triphenylphosphine)rhodium(I) as the hydrogenation catalyst (R.H. Fish. J.L. Tan and A. D. Thormodsen, J. org. Chem., 1984, 4500). 

Selective reduction of both double bonds in a,jS-unsaturated carbonyl compounds that also contain an isolated olefin is possible with appropriate catalyst and reaction conditions . Chlorotris(biphenylphosphine)rhodium hydrogenates the isolated double bond. Thus, carvone, 13, is reduced to dihydrocarvone, 14, with careful measure of the uptake of Hj ... 

Hydridotetrakis(triphenylphosphine)rhodium(I) has previously been prepared by addition of triphenylphosphine to preformed hydridotris(triphenylphosphine)rhodium(I) in toluene solution23,24 and by reaction of preformed chlorotris(triphenylphosphine)-rhodium(I) with hydrazine and hydrogen in an ethanol-benzene medium containing excess triphenylphosphine.23 Other syntheses employ aluminum alkyls,25 Grignard reagents,26 sodium prop-oxide,27 and hydrogen under pressure28 as reductants. 

Similarly, reduction of the unsaturated lactone 4 by hydrogenation over palladium on carbon yielded only the tetrasubstituted monohydrogenated product. In this case Wilkinson s catalyst [chlorotris(triphenylphosphane)rhodium] is the catalyst of choice for the regio- and diastereose-lective reduction of the exocyclic double bond7. 

A solution of 290 mg (1.11 mmol) of diene 4 and 100 mg of chlorotris(triphenylphosphane)rhodium in 34 mL of benzene is hydrogenated at 760 Torr for 12 h. The volatiles are removed in vacuo and the residue is stirred with 50 mL of Et20. The solids are filtered through Celite and the filtrate is concentrated in vacuo to afford an oily residue which is chromatographed on silica gel (36 g). Elution with benzene/Lt20 (20 1) affords 5 as a light brown oil [yield 223 mg (76%)] which slowly crystallizes mp 88-90 JC. 

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