Rhodium oximes

Costa G., Tavagnacco C., Mahajan R. Electrocatalytic dioxygen reduction in the presents of cobalt and rhodium-oximes complexes. Bulletin of electrochemistry 1998 14(2) 78-85. 

Other hydrogenation methods are less chemoselective. Use of Raney nickel provides hydroxylamines in low yield °. Hydrogenation of 1-acetonaphthone oxime over rhodium-chiral phosphine catalysts was found to proceed under harsh conditions and provided low... 

Nonsteroidal antiinflammatory drugs, interaction with lithium, 36 66 No-phonon transition, 35 324 Norbomadiene complexes with cobalt, 12 286 with copper, 12 328, 330, 331 with gold, 12 348, 349 with group VIB metals, 12 231 with group VnB metals, 12 241 with iron, 12 265 with palladium, 12 314 with platinum, 12 319 with rhodium, 12 300-302 with ruthenium, 12 278, 279 with silver, 12 340-342, 344, 346 Norbomylsiloxane, 42 226, 228 Notch receptor proteins, 46 473, 475 h (N)" oxime complexes, osmium, 37 260 h (N,0) oxime complexes, osmium, 37 260 (NPr ljiFeCfrdto),], magnetization versus temperature, 43 230... 

Heterogeneous hydrogenation of the C=N bond is a very widely used synthetic process with application to small and large-scale reactions. Many of the catalysts described in other sections may also be employed, for example those based on supported rhodium, palladium etc, and Raney Nickel. This area has been reviewed extensively recently192. Hydrogenation of oximes and hydrazones results in formation of amines. Milder conditions can be used for oxime reduction if the ethylaminocarbonyl derivative is prepared in situ prior to reduction276. 

The formation and intramolecular dipolar cycloaddition of azomethine ylides formed by carbenoid reaction with C=N bonds has recently been studied by the authors group.84 Treatment of 2-(diazoace-tyl)benzaldehyde O-methyl oxime (176) with rhodium(II) octanoate in the presence of dimethyl acetylenedicarboxylate or N-phenylmaleimide produced cycloadducts 178 and 179, respectively. The cycloaddition was also carried out using p-quinone as the dipolarophile. The major product isolated corresponded to cycloadduct 180. The subsequent reaction of this material with excess acetic anhydride in pyridine afforded diacetate 181 in 67% overall yield from 176. The latter compound incorporates the basic dibenzofa, d -cyclohepten-5,10-imine skeleton found in MK-801,85 which is a selective ligand for brain cyclidine (PCP) receptors that has attracted considerable attention as a potent anticonvulsive and neuro-protective agent.86,87... 

The oxime nitrogen lone pair of electrons must be properly oriented so as to interact with the rhodium carbenoid.84 Thus, subjection of the -oximino isomer 182 to a catalytic quantity of Rh2(OAc)4 in CH2C12 (40 °C) with a slight excess of DMAD afforded the bimolecular cycloadduct 184 in 93% yield. In sharp contrast, when the isomeric Z-oximino diazo derivative 183 was exposed to the same reaction conditions, only indanone-oxime 185 (80%) was obtained. The formation of this product is most likely the result of an intramolecular C-H insertion reaction. 

The formation and intramolecular dipolar cycloaddition of azomethine ylides formed by carbenoid reaction with C-N double bonds has recently been studied by the author s group [66]. Treatment of 2-(diazoacetyl)benzaldehyde O-methyl oxime (118) with rhodium (II) octanoate in the presence of dimethyl acetylenedicarboxylate or iV-phenylmaleimide produced cycloadducts 120 and... 

An intramolecular rhodium-catalyzed [2+2+2] cycloaddition of diynenitriles <07OL1295> diyne esters <07T12853> and alkynevinyl oximes <07TL6852> also afforded pyridine versions of dihydrobenzo[c]furans. Trost prepared these pyridine derivatives employing a similar ruthenium-catalyzed cycloisomerization-6 cyclization route as depicted in the following scheme <07OL1473>. 

A synthesis of a set of 2-pyridylpyrroles has been described, involving annulation of 1,3-dicarbonyl compounds with 2-(aminomethyl)pyridine under acidic conditions, as illustrated by the construction of compound 437 (Equation 121) <20020L435>. Likewise, pyrroles have also been obtained from reactions between 1,3-diaryl-l,3-dicarbonyl compounds and imines or oximes promoted by the TiCU/Zn-system <2004SL2239>. Yet another approach involves rhodium-catalyzed reactions of isonitriles with 1,3-dicarbonyl synthons, which enables for instance preparation of fluorinated pyrroles <20010L421>. 

There are some reports on the asymmetric catalytic hydrogenation of C=N double bonds. Rhodium phosphine complexes do not have high activity, and the stereoselectivity is low. - Homogeneous hydrogenation of oximes, Schiff s bases and cyclic imines " have been reported. A cyano cobalt complex has been used for the homogeneous catalytic hydrogenation of oximes and Schiff s bases but the degree of asymmetric induction is unknown. 

Cycloheptanone oxime can be converted into the amine in good yield by high-pressure hydrogenation of the oxime with Raney nickel and ammonia, but Freifelder " found that the reaction is so strongly exothermal that on a large scale it may get out of hand. He then found that the hydrogenation can be accomplished smoothly by low-pressure hydrogenation in the presence of rhodium-alumina. The temperature was allowed to rise spontaneously to 60° and kept there until reduction... 

Hydrogenation is selective for size and shape.200 Cyclohexene, but not cyclododecene, was reduced by hydrogen with a rhodium in NaY zeolite. The Beckmann rearrangement of cyclohexanone oxime to caprolactam (6.37) (for... 

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