Rhodium compounds reaction with diazoketones

Where the carbon-carbon double bond is a part of an aromatic system, in general, cyclopropanation of diazoketones results in the formation of unstable cyclopropane adducts. For example, Saba140 has shown that in the intramolecular cyclopropanation of diazoketone 57 the norcaradiene ketone 58 can be detected by low-temperature NMR and can be trapped in a Diels Alder reaction with 4-phenyl-l,2,4-triazoline-3,5-dione (equation 69). In addition, Wenkert and Liu have isolated the stable norcaradiene 60 from the rhodium catalysed decomposition of diazoketone 59 (equation 70)105. Cyclopropyl ketones derived from intramolecular cyclopropanation of hetereoaromatic diazoketones are also known and two representative examples are shown in equations 71 and 72106. Rhodium(II) compounds are the most suitable catalysts for the cyclopropanation of aromatic diazoketones. 

The formation of thiocarbonyl ylids by the reaction of metallocarbenoids with thiocarbonyl compounds has not been extensively studied, as noted by Padwa and Weingarten in a review [167]. However, formation of rings by interaction of these compounds has recently received some attention. A key step in the synthesis of a polyhydroxylated indolizidine alkaloid related to castanospermine is the reaction of diazoketone with a thioamide, in the presence of rhodium acetate [135]. After desulfurisation an enaminone was obtained. 

Diazoketones also undergo macrocyclic aromatic cycloaddition reactions. Decomposition of 108 with rhodium(II) prefluorobutyrate yields aromatic cycloaddition products 109 and 110 in 30% and 9% yield, respectively. When cycloheptatriene 109 is exposed to neutral alumina, isomerization to 111 occurs. It is interesting that the 1,4-isomer 110 is inert to rearrangement on both silica and alumina. The ability to formally connect a carbene to a remote aromatic ring provides new opportunities for the construction of macrocyclic compounds. 

Rhodium(II) acetate was found to be much more superior to copper catalysts in catalyzing reactions between thiophenes and diazoesters or diazoketones 246 K The outcome of the reaction depends on the particular diazo compound 246> With /-butyl diazoacetate, high-yield cydopropanation takes place, yielding 6-eco-substituted thiabicyclohexene 262. Dimethyl or diethyl diazomalonate, upon Rh2(OAc)4-catalysis at room temperature, furnish stable thiophenium bis(alkoxycarbonyl)methanides 263, but exclusively the corresponding carbene dimer upon heating. In contrast, only 2-thienylmalonate (36 %) and carbene dimer were obtained upon heating the reactants for 8 days in the presence of Cul P(OEt)3. The Rh(II)-promoted ylide formation... 

Polymer-supported benzenesulfonyl azides have been developed as a safe diazotransfer reagent. ° These compounds, including CH2N2 and other diazoalkanes, react with metals or metal salts (copper, paUadium, and rhodium are most commonly used) to give the carbene complexes that add CRR to double bonds. Diazoketones and diazoesters with alkenes to give the cyclopropane derivative, usually with a transition-metal catalyst, such as a copper complex. The ruthenium catalyst reaction of diazoesters with an alkyne give a cyclopropene. An X-ray structure of an osmium catalyst intermediate has been determined. Electron-rich alkenes react faster than simple alkenes. ... 

Rhodium(II) acetate was found to be much more superior to copper catalysts in catalyzing reactions between thiophenes and diazoesters or diazoketones The outcome of the reaction depends on the particular diazo compound With f-butyl... 

The intramolecular Buchner reaction of aryl diazoketones has been carried out using both copper(I) and rhodium(II) catalysts. For example, 1-diazo-4-phenylbutan-2-one 27a cyclizes in bromobenzene with copper(I) chloride catalysis, furnishing 3,4-dihydroazulen-l(2//)-one 30 in 50% yield after purification by chromatography over alumina. Trienone 30 is not the primary cyclization product, and the less conjugated isomeric trienone 29a is first produced, but contact with alumina causes isomerization to 30. The yield of this cyclization is further improved when rhodium(II) acetate is used as the catalyst instead of copper(I) chloride. Thus a catalytic amount of rhodium(II) acetate brings about the nearly quantitative conversion of 27a to 29a within minutes in hot dichloromethane. Compound 29a isomerizes to 30 on treatment with triethylamine, and rearranges to 2-tetralone 31a when exposed to silica gel or acid. 

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