Rhodium acetate dimer

Dihydro-5-hydroxy-5//-benz[Z ]azepines (200) are formed in high yields by rhodium-catalyzed, kinetically controlled hydroformylation of the aminoalkenes (199) at high pressures <92AJC2l>. The reactions were carried out using the substrate, rhodium acetate dimer, and triphenyl phosphine in the ratio 200 1 4 at 2760 kPa at 60 C. A small amount of 3-alkyl-isoquinoline is formed in all cases. 

Insertion of carbenoid species into the azetidinone N-H bond is the most straightforward route to 2-oxocarbapenams, and thence to the vast majority of carbapenem antibiotics [186]. Unfortunately, synthesis of the 2-oxopenam 281a (R" = Me) from diazomalonic azetidinyl thioester 323 was abortive [172,187]. The prescribed carbene was generated (rhodium acetate dimer or hv), but it underwent Wolff rearrangement to a ketene. 

In 1989, the Moody s group from UK reported the constmction of seven-membered cyclic ethers (Fig. 3.26) [9] via Rh (Il)-catalyzed intramolecular O-H insertion reaction. With the catalyst of rhodium acetate dimer, the catenulate a-diazo carbonyl substrate containing secondary hydroxyl reacted to obtain seven-membered cyclic ethers under toluene reflux conditions with the yield of 88 %. 

A 1 2 mixture of isomeric cis-3,4a-H- and fra s-3,4a-H-3-methyl-2,3,4, 4a,5,6-hexahydro-l//-pyrido[l,2-a]quinazolines gave a 20 1 mixture in the presence of rhodium(II) acetate dimer and triphenylphosphine in ethyl acetate at 80°C for 20 h (94AJC1061). Epimerization probably occurs via a 10-membered ring intermediate (26). 

Rhodium-catalyzed hydroformylation of 2-amino-/V-(but-3 -enyl)- and -A-(3 -rnethylbut-3 -enyi)benzylamines (381) in the presence of rho-dium(II) acetate dimer and triphenylphosphine in deoxygenated ethyl acetate gave mixtures of 5,5a,6,7,8,9-hexahydro-llH-pyrido[2,l-b]quinazo-line (382), isomeric 6-methyl-5,5a,6,7,8,10-hexahydropyrrolo[2,l-b]quina-zolines (383), and 6-methyl-6,7,8,10-tetrahydropyrrolo[2,l-ft]quinazoline (384), as well as a stereoisomeric mixture of 7-methyl-5,5a,6,7,8,9-hexahy-dro-ll//-pyrido[2,l-b]quinazolines (385) and 15% of 7-methyl-6,7,8,9-tetrahydro-llH-pyrido[2,l-fr)quinazolme (386), (95AJC2023). When the bulky tricyclohexylphosphine was used instead of triphenylphosphine, a 3 7 mixture of compounds 382 and 383 and a 3 1 mixture of isomeric 385 were formed. 

Rhodium-catalyzed hydroformylation of -(substituted amino)benzyl-amines (387, X = H2) and -(substituted amino)benzamides (387, R = H, X = O) in the presence of rhodium(II) acetate dimer and triphenylphos-phine in deoxygenated ethyl acetate gave a 7 3 mixture of 1,2,3,4,4 ,5-hexahydro-6//-pyrido[l,2-a]quinazolines (388, X = H2,0) and isomeric 3-methyl-l,2,3,3fl,4,5-hexahydropyrrolo[l,2-a]quinazolines (389, X = H2, O) (94AJC1061). The methyl derivative of benzylamine 387 (R = Me, X = H2) afforded a mixture of diastereoisomers 390 and 391 (X = H2). Their ratio depended on the reaction time. Longer reaction times gave more 391 (X = H2), containing the methyl group in an equatorial position. Compound 390 isomerized into 391 (X = H2), under the aforementioned conditions. The benzamide derivative (387, R = Me, X = O) yielded only one isomer (391, X = O), independent of the reaction period. 

The cyclopropanation of alkenes, alkynes, and aromatic compounds by carbenoids generated in the metal-catalyzed decomposition of diazo ketones has found widespread use as a method for carbon-carbon bond construction for many years, and intramolecular applications of these reactions have provided a useful cyclization strategy. Historically, copper metal, cuprous chloride, cupric sulfate, and other copper salts were used most commonly as catalysts for such reactions however, the superior catalytic activity of rhodium(ll) acetate dimer has recently become well-established.3 This commercially available rhodium salt exhibits high catalytic activity for the decomposition of diazo ketones even at very low catalyst substrate ratios (< 1%) and is less capricious than the old copper catalysts. We recommend the use of rhodium(ll) acetate dimer in preference to copper catalysts in all diazo ketone decomposition reactions. The present synthesis describes a typical cyclization procedure. 

Rhodium diacetate dimer Acetic acid, rhodium(2+) salt (8,9) (5503-41-3)... 

The first step was development of a catalytic epoxidation cycle using stoichiometric amounts of achiral sulfides and rhodium acetate [212-214]. The nucleophilicity of the sulfide plays a key role. In addition, the absence of sulfides led to the formation of stilbenes, and homologated products were formed in the absence of rhodium acetate [214]. This emphasizes that the sulfide and the rhodium catalyst were required for the operation of the catalytic cycle shown in Scheme 6.87B [214], It was also found that the reaction proceeded to completion with catalytic amounts of the sulfide. A prerequisite is slow addition of the diazo compound over a longer period of time, e.g. 24 h, to avoid the assumed dimerization of the diazo compound as a competing reaction under those conditions [214, 215]. 

To a 10-mL round-bottomed flask fitted with a nitrogen balloon was added sulfide catalyst (0.2 equiv), anhydrous dioxane (4.0 mL), rhodium(II) acetate dimer (2 mg, 0.01 equiv), substrate (0.5 mmol), benzyl triethylammonium chloride (23 mg, 0.2 equiv), and tosylhydrazone sodium salt (1.5 equiv). The reaction mixture was stirred vigorously at 40 °C for 48 h. Work-up consisted of the sequential addition to the reaction mixture of water (5 mL) and ethyl acetate (5 mL). The aqueous layer was washed with ethyl acetate (2.5 mL) and the combined organic phases dried (MgSC ), filtered, and concentrated in vacuo. The crude products were analyzed by aH NMR to determine the diastereomeric ratio, and then purified by FC to afford the corresponding cyclopropane. 

Triethylamine, dimethyl malonate, and rhodium(ll) acetate dimer were purchased from Aldrich Chemical Company, Inc., and used without further purification. 

Rhodium(ll) acetate dimer Rhodium, tetrakis(acetato-0,0 )di-, (Rh-Rh) (9) (46847-37-4)... 

A stirred solution of tetrahydrothiophene (0.066 mol), rhodium(II)acetate dimer (0.003 mmol), benzyltriethylammonium chloride (0.066 mmol) and benzaldehyde (0.33 mol) dissolved in 1ml acetonitrile was added to the product from Step 1 (0.495 mmol). The mixture was heated to 45 °C 3 hours, cooled, and 1 ml EtOAc/water, 1 1, added. The organic phase was dried, the epoxide purified by chromatography on silica with CH2Cl2/petroleum ether, 0-25%, and the product isolated. 

Rhodium(II) acetate dimer was purchased from Alfa Aesar Company and used as received. 

Heterofunctionalized derivatives can be prepared following the same methodology. In the case of esters and halides, rhodium(II) acetate dimer must be employed as catalyst instead of copper compounds.After transformation of the acetoxymethyl group of 7 (X = OAc) into an ester functionality, these compounds are valuable precursors of highly functionalized bi-cyclo[1.1.0]butanes since nucleophilic attack on the keto group takes place under very mild conditions. Thus, the t> /o-bicyclo[1.1.0]butane-l,2,3-tricarboxylic ester is obtained from 3-oxo-tricyclo[2.1.0.0 - ]pentane-l, 5-dicarboxylic esters upon treatment with methanol at 20 °C for three hours. 

A solution of l,2-bis(acetoxymethyl)-3-(diazoacetyl)cydopropene (6, X = OAc) (195 mg, 8 mmol) in EtOH-free CHCI3 (10 mL) was added dropwise with stirring to a solution of rhodium(II) acetate dimer... 

Photochemical decomposition of diazo(trimethylsilyl)methane (1) in the presence of alkenes has not been thoroughly investigated (see Houben-Weyl Vol. E19b, p 1415). The available experimental data [trimethylsilylcyclopropane (17% yield) and la,2a,3j8-2,3-dimethyl-l-trimethylsilylcyclopropane (23% yield)] indicate that cyclopropanation occurs only in low yield with ethene and ( )-but-2-ene. In both cases the formal carbene dimer is the main product. In reactions with other alkenes, such as 2,3-dimethylbut-2-ene, tetrafluoroethene or hexafluoro-propene, no cyclopropanes could be detected.The transition-metal-catalyzed decomposition of diazo(trimethylsilyl)methane (1) has been applied to the synthesis of many different silicon-substituted cyclopropanes (see Table 3 and Houben-Weyl Vol.E19b, p 1415) 3.20a,b,2i.25 ( iQp. per(I) chloride has been most commonly used for carbene transfer to ethyl-substituted alkenes, cycloalkenes, styrene, and related arylalkenes. For the cyclopropanation of acyl-substituted alkenes, palladium(II) chloride is the catalyst of choice, while palladium(II) acetate was less efficient, and copper(I) chloride, copper(II) sulfate and rhodium(II) acetate dimer were totally unproductive. The cyclopropanation of ( )-but-2-ene represents a unique... 

The transition-metal-catalyzed decomposition of methyl trialkylsilyldiazoacetates 5 in the presence of styrene, hex-l-ene and cyclohexene has been studied.In all cases, where cyclopropanation occurs, the formation of the thermodynamically favored cyclopropane dia-stereomers E-6 and anti-1 are formed predominantly. The steric demand of the trialkylsilyl substituent has a relatively small influence on the diastereoselectivity on the other hand, catalytic cyclopropanation with the triisopropylsilyldiazoacetate is more difficult than with 5 (R = Me, Et) or fails completely. Copper(I) triflate is a more efficient catalyst for these cyclo-propanations than rhodium(II) acetate dimer and rhodium(II) bis(perfluorobutanoate) dimer the catalyst [Ru2(CO)4(/i-OAc)2] gives somewhat better results than copper(I) triflate for hex-l-ene, but not for styrene. The catalytic cyclopropanation of cyclohexene with 5 (R = Me, Et) to give bicyclo[4.1.0]heptanes 7 succeeds only with [Ru2(CO)4(/j-OAc)2] as catalyst. ... 

Diazo compound 2 is obtained by thermal ring opening of the bicyclic pyrazoline 1." Catalytic decomposition of 2 with copper(I) iodide in refluxing benzene yields the bicyclo[1.1.0]butane 3. The same result is achieved with bis(acetonitrile)palladium(II) chloride as catalyst, whereas rhodium(II) acetate dimer and copper(I) cyanide are unreactive. 

A solution of ( , )-hexa-2,4-dienyl ( )-2-diazo-4-phenylbut-3-enoate (4, R = R == H R = Me 1.201 g, 5 mmol) in CH2CI2 (10 mL) was added dropwise over 10 min to a stirred mixture of rhodium(II) acetate dimer (21 mg, 0.05 mmol) in dry CH2CI2 (10 mL) and heated under reflux in an argon atmosphere for 10 min. The solvent was evaporated under reduced pressure and the residue was purified by column chromatography (silica gel, EtOAc/hexane 1 9) to give a colorless solid yield 0.913 g (76%) mp 104-106°C. 

A solution of diazo ester 23 (1 equiv) in dry CH2CI2 was added dropwise to a refluxing mixture of the diene 24 (5 equiv) and rhodium(II) acetate dimer (0.01 equiv) in dry CHjClj under an argon atmosphere. After the addition was complete, the mixture was refluxed for an additional 0.5 h. The mixture was then cooled and concentrated under vacuum to yield the crude product. 

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