Rhodium sulfur containing

In recent years, the asymmetric hydrogenation of prochiral olefins have been developed in the presence of various chiral sulfur-containing ligands combined with rhodium, iridium or more rarely ruthenium catalysts. The best results have been obtained by using S/P ligands, with enantioselectivities of up to 99% ee in... 

McKervey and Ye have developed chiral sulfur-containing dirhodium car-boxylates that have been subsequently employed as catalysts for asymmetric intramolecular C-H insertion reactions of y-alkoxy-ot-diazo-p-keto esters. These reactions produced the corresponding ci -2,5-disubstituted-3(2H)-furanones with diastereoselectivities of up to 47% de. Moreover, when a chiral y-alkoxy-a-diazo-p-keto ester containing the menthyl group as a chiral auxiliary was combined with rhodium(II) benzenesulfoneprolinate catalyst, a considerable diastereoselectivity enhancement was achieved with the de value being more than 60% (Scheme 10.74). 

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. ... 

Recently, the known method for the synthesis of thiolanes by cyclization of diazo ketosulfides (72CC860) has received further development (92TL169 95JOC53). It was found that sulfur-containing a-diazo ketones 437 bearing a tethered alkyne unit decomposed in the presence of Rh2(OAc)4 via the addition of the rhodium-stabilized carbenoid onto the acetylene jr-bond to give a vinyl carbenoid, followed by sulfonium ylide formation and a subsequent [2,3]- or [l,2]-sigmatropic shift. This transfor-... 

Like thiophene, selenophene derivatives react with dimethyl diazomalonate in the presence of rhodium acetate to give ylides (17) which are less stable than their sulfur-containing congeners <84CS253>. 

Karatzas et al. [34] investigated the performance of rhodium catalyst containing 3 wt.% rhodium, 10 wt.% ceria, 10 wt.% lanthana on alumina carrier for the autothermal reforming of n-tetradecane, low sulfur diesel containing 6 ppm sulfur, and Fischer-Tropsch diesel over cordierite monolithic reactors. At temperatures exceeding 740°C, full conversion of the feed was achieved. 

As stated earlier, the number of possibilities for reaction of these species with radiation-induced radicals is large and the exact mechanism may be different from that suggested by the above reaction. In recent results the in vitro sensitizing action of rhodium carboxylates has been attributed to their thiol binding capacity [58], and this is of interest in view of their known affinity for sulfur-containing cellular constituents (see Chapter 6). The in vitro sensitizing efficiency of the carboxylates follows the order butyrate > propionate > acetate > methoxyacetate, which parallels the antitumour effect and is related to the intracellular uptake. The sensitiza-... 

Cases of the S-coordinated rhodium and iridium are quite scarce. To complete the picture, we next consider the possibilities of S-coordination using complicated derivatives of thiophene. 2,5-[Bis(2-diphenylphosphino)ethyl]thiophene is known to contain three potential donor sites, two phosphorus atoms and the sulfur heteroatom, the latter being a rather nucleophilic center (93IC5652). A more typical situation is coordination via the phosphorus sites. It is also observed in the product of the reaction of 2,5-bis[3-(diphenylphosphino)propyl]thiophene (L) with the species obtained after treatment of [(cod)Rh(acac)] with perchloric acid (95IC365). Carbonylation of [Rh(cod)L][C104]) thus prepared yields 237. Decarbonylation of 237 gives a mixture of 238 and the S-coordinated species 239. Complete decarbonylation gives 240, where the heterocycle is -coordinated. The cycle of carbonylation decarbonylation is reversible. 

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