Ylide homogeneous catalyst

We found that the reaction of bis(cyclooctadiene)nickel(0) with the two ylides ben-zoyhnethylene-triphenylphosphorane and methylene-trimethylphosphorane in toluene yields a highly active homogeneous catalyst (la) without any co-catalyst -the ethylene turnover being approximately tenfold compared to 2 [10]. 

Rhodium(II) acetate catalyzes C—H insertion, olefin addition, heteroatom-H insertion, and ylide formation of a-diazocarbonyls via a rhodium carbenoid species (144—147). Intramolecular cyclopentane formation via C—H insertion occurs with retention of stereochemistry (143). Chiral rhodium (TT) carboxamides catalyze enantioselective cyclopropanation and intramolecular C—N insertions of CC-diazoketones (148). Other reactions catalyzed by rhodium complexes include double-bond migration (140), hydrogenation of aromatic aldehydes and ketones to hydrocarbons (150), homologation of esters (151), carbonylation of formaldehyde (152) and amines (140), reductive carbonylation of dimethyl ether or methyl acetate to 1,1-diacetoxy ethane (153), decarbonylation of aldehydes (140), water gas shift reaction (69,154), C—C skeletal rearrangements (132,140), oxidation of olefins to ketones (155) and aldehydes (156), and oxidation of substituted anthracenes to anthraquinones (157). Rhodium-catalyzed hydrosilation of olefins, alkynes, carbonyls, alcohols, and imines is facile and may also be accomplished enantioselectively (140). Rhodium complexes are moderately active alkene and alkyne polymerization catalysts (140). In some cases polymer-supported versions of homogeneous rhodium catalysts have improved activity, compared to their homogenous counterparts. This is the case for the conversion of alkenes direcdy to alcohols under oxo conditions by rhodium—amine polymer catalysts... 

Homogeneous ylide-nickel systems were combined with heterogeneous surface chromium(II) catalysts. Both separate catalyst systems work in the absence of aluminum alkyl co-catalysts. In this process the nickel complex is supported on the chromium contact, resulting in a new heterogeneous catalyst, which is active in the ediylene polymerization and where two different catalytic centers co-operate [14a, b]. 

A modified, o-alkoxy-substituted ylide 783 has an improved solubility in nonpolar solvents, such as aromatic hydrocarbons and has a generally higher reactivity than ylide 781 [1069]. In particular, ylide 783 is a useful reagent for the preparation of oxazole derivatives 784 in the reaction with carbodiimides 782 under homogeneous conditions in the presence of Rh(II) or Cu(II) catalysts (Scheme 3.309) [1069]. 

The entire process is schematized on Figure 4. In the first step, ethylene is oligomerized in the presence of a homogeneous nickel phosphine catalyst. This catalyst is a nickel hydride generated by reduction of a nickel salt in the presence of a chelating ligand such as diphenylphosphinobenzoic acid or by reaction of nickel(O) with a phosphorus ylide. 

Thus, Simonneaux and co-workers have reported treatment of methyl allyl sulphide with 2-diazoethyl acetate at 25 in the presence of (SBF>4PRuCO as catalyst (homogeneous reaction, entry 1 in Table 4), which leads to ethyl-2-(methylthio)pent-4-enoate in 88 % yield with 8 % of dimers [56]. As presented in Scheme 21, the formation of ethyl-2-(methylthio)pent-4-enoate derives from the [2,3]-sigmatropic rearrangement of the sulphur ylide and that of the dimers (di-ethylfumarate and diethylmaleate) derives from 2-diazoethyl acetate dimerization. 

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