Tris rhodium chloride

The replacement of rhodium from a wide range of rhodacycles to form condensed furans, thiophenes, selenophenes, tellurophenes and pyrroles has been widely explored and a range of examples is shown in Scheme 97. The rhodacycles are readily generated from the appropriate dialkyne and tris(triphenylphosphine)rhodium chloride. Replacement of the rhodium by sulfur, selenium or tellurium is effected by direct treatment with the element, replacement by oxygen using m-chloroperbenzoic acid and by nitrogen using nitrosobenzene. 

The reduction of keto steroids by treatment with chloroiridic acid, or sodium chloroiridate, and trimethyl phosphite has been studied in some detail.Ketones at the 2- and 3-positions are reduced predominantly to the corresponding axial alcohols, while ketones at 4,6,7,11,12,17 and 20 are not affected. The rate of reaction is increased by addition of aqueous sodium hydroxide. Replacement of sodium chloroiridate by tris(triphenylphos-phine)rhodium chloride gives a system which reduces a 3-keto steroid to the... 

The eliminaUon of carbon monoxide from nonfluonnated acyl fluorides, however, does not result in a fluonne compound Although it was claimed earlier that benzoyl fluoride can be converted into fluorobenzene by using tris(triphenyl-phosphme)rhodium chloride, recent studies proved that the product is benzene and not fluorobenzene [91]... 

Wender et al. have demonstrated the power of the rhodium-catalyzed [5 + 2]-cycload-dition reaction discovered in their laboratories by synthesizing (+)-dictamnol (148) [33], Allenylvinylcyclopropane 145 was treated with rhodium biscarbonyl chloride dimer or rhodium tris(triphenylphosphine) chloride (Scheme 19.27). Both catalysts provided the cycloadduct 146 in 70-76% yield and high diastereoselectivity (8-9 1). The diaster-eoselectivity was attributed to the C8 hydroxyl group assuming a position on the less sterically encumbered exo face of the transition-state structure 147. 

Many catalysts, certainly those most widely used such as platinum, palladium, rhodium, ruthenium, nickel, Raney nickel, and catalysts for homogeneous hydrogenation such as tris(triphenylphosphine)rhodium chloride are now commercially available. Procedures for the preparation of catalysts are therefore described in detail only in the cases of the less common ones (p. 205). Guidelines for use and dosage of catalysts are given in Table 1. 

Divalent sulfur is a poison for most noble metal catalysts so that catalytic hydrogenation of sulfur-containing compounds poses serious problems (p. 10). However, allyl phenyl sulfide was hydrogenated over tris trisphenyl-phosphine)rhodium chloride in benzene to give 93% yield of phenyl propyl sulfide [674. ... 

Reduction of the double bond only was achieved by catalytic hydrogenation over palladium prepared by reduction with sodium borohydride. This catalyst does not catalyze hydrogenation of the aldehyde group [31]. Also sodium borohydride-reduced nickel was used for conversion of cinnamaldehyde to hydrocinnamaldehyde [31]. Homogeneous hydrogenation over tris(triphenylphosphine)rhodium chloride gave 60% of hydrocinnamaldehyde and 40% of ethylbenzene [5(5]. Raney nickel, by contrast, catalyzes total reduction to hydrocinnamyl alcohol [4S. Total reduction of both the double... 

Hydrogenation of phthalic anhydride over copper chromite afforded 82.5% yield of the lactone, phthalide, and 9.8% of o-toluic acid resulting from hydrogenolysis of a carbon-oxygen bond [1015]. Homogeneous hydrogenation of a,a-dimethylsuccinic anhydride over tris(triphenylphos-phine)rhodium chloride gave 65% of a,a-dimethyl- and 7% of )S,)S-dimethyl-butyrolactone [1016]. 

Methyl cinnamate was reduced quantitatively to methyl 3-phenylpropa-noate by hydrogen over colloidal palladium at room temperature and atmospheric pressure [7057] ethyl cinnamate was reduced to ethyl 3-phenyIpropa-noate over tris(triphenylphosphine)rhodium chloride in ethanol at 40-60° and 4-7 atm in 93% yield [55], and over copper chromite at 150° and 175 atm in 97% yield [420]. On the other hand, hydrogenation of ethyl cinnamate over... 

Preparation of the Catalyst Tris(triphenylphosphine)rhodium Chloride [57]... 

Rhodium chloride trihydrate (1 g, 5.2 mmol) and triphenylphosphine (6 g, 23 mmol) are refluxed in 120 ml of ethanol. The solid tris(triphenylphosphine)rhodium chloride is filtered with suction and washed with ethanol and ether. Yield is 3.5 g (73%). 

The isomerization of allyl ethers to 1-propenyl ethers, which is usually performed with potassium tert-butoxide in dimethyl sulfoxide, can also be carried out under milder conditions using tris(triphen-ylphosphine)rhodium chloride,208 and by an ene reaction with diethyl azodicarboxylate,209,210 which affords a vinyl ether adduct. Removal of an O-allyl group may be achieved by oxidation with selenium dioxide in acetic acid,211 and by treatment with N-bromosuccinimide, followed by an aqueous base.201,212... 

The reaction of bis-phenylpropargyl ether (321) with tris(triphenylphosphine)rhodium chloride in benzene or toluene led to the formation of the unusual organometallic compound (322), which can be viewed as a derivative of an oxygen-rhodium pentalene system. Reaction of the rhodium complex (322) with sulfur leads to the corresponding 4,6-diphenyl-l,3-dihydro[3,4-c]furan (323). The selenium and tellurium analogs (324) and (325) were made in a similar manner (Scheme 111) (76LA1448). 

Previous work has shown that the electronic characteristics of the benzene substituent in triarylphosphine chlororhodium complexes have a marked influence on the rate of olefin hydrogenation catalyzed by these compounds. Thus, in the hydrogenation of cyclohexene using L3RhCl the rate decreased as L = tri-p-methoxyphenylphosphine > triphenylphosphine > tri-p-fluorophenylphosphine (14). In the hydrogenation of 1-hexene with catalysts prepared by treating dicyclooctene rhodium chloride with 2.2-2.5 equivalents of substituted triarylphosphines, the substituent effect on the rate was p-methoxy > p-methyl >> p-chloro (15). No mention could be found of any product stereochemistry studies using this type of catalyst. 

The activity of homogeneous catalysts also has been demonstrated Wilkm son s catalyst tris(triphenylphosphine) rhodium chloride induces petfluoroalkyl iodides to add to olefins at 80 °C [10] (equation 10) Tetrakis(tnphenylphosphme)-palladtum promotes the addition to both alkenes and alkynes in hexane [11] Amines and amine salts induce addition at 120-140 °C [12] (equation 11)... 

The tris(triphenylphosphine)rhodium chloride catalyst was prepared according to the procedure of G. Wilkinson and co-workers.4... 

Recently, it has been discovered that catalysis by rhodium compounds is more effective than by the older cobalt catalyst when tris(triphenylphosphine)rhodium chloride is treated with carbon monoxide, the catalyst bis(triphenylphosphine)rhodium carbonyl chloride is formed. This catalyst is very effective under very mild conditions (49-51). It is believed that the tr-ir rearrangement is also important with this catalyst and operates in a manner analogous to that in the cobalt-catalyzed process, since stablization of the cr complex has been shown to lead to olefin isomerization and lower linear selectivity (52). 

P-31 NMR was a powerful tool in studies correlating the structure of tertiary-phosphine-rhodium chloride complexes with their behavior as olefin hydrogenation catalysts. Triphenylphosphine-rhodium complex hydrogenation catalyst species (1) were studied by Tolman et al. at du Pont and Company (2). They found that tris(triphenylphosphine)rhodium(I) chloride (A) dissociates to tri-phenylphosphine and a highly reactive intermediate (B). The latter is dimerized to tetrakis(triphenylphosphine)dirhodium(I) dichloride (C). 

Reduction of the amide (123 R1 = R2 = OMe) with sodium aluminium hydride gave a mixture of the bases (125 R1 = R2 = OMe), (127), and (130),165 and the last of these lost carbon monoxide when heated with tris(tri-phenylphosphine)rhodium chloride in benzene to give the dimethyl ketal of 14/3-methylcodeinone, which could be hydrolysed to 14j8-methylcodeinone, the 7,8-dihydro-derivative of which proved to be identical with material previously prepared by a different route (see Volume 9, p. 116). The corresponding morphinone and dihydromorphinone have been prepared.164... 

Some positional isomers of coralyne have been synthesized and examined for antileukaemic activity,82 and the distribution of salts of coralyne after they have been administered to rodents has been studied.83 Dehydrogenation of canadine to berberrubine (59) can be accomplished in ethylene glycol and hydrochloric acid with palladium or with tris(triphenylphosphinyl)rhodium chloride, the reaction proceeding faster at low temperatures with the latter catalyst.84 Derivatives of 13-methylberberrubine and its analogues have been synthesized, so that they might be screened to find their potential as antitumour agents.85... 

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