Rhodium tetraacetate

The use of dirhodium(II) catalysts for catalytic reactions with diazo compounds was initiated by Ph. Teyssie [14] in the 1970s and rapidly spread to other laboratories [1]. The first uses were with dirhodium(II) tetraacetate and the more soluble tetraoctanoate, Rh2(oct)4 [15]. Rhodium acetate, revealed to have the paddle wheel structure and exist with a Rh-Rh single bond [16], was conve-... 

Ether Formation with Ethyldiazoacetate. Disperse Red 1 (2.0 g, 1.0 eq.) and rhodium tetraacetate [Rh2(OAc)4] (47 mg, 0.016 eq.) are dissolved in DCM-toluene (1 1, 50 ml) in a dry two-neck round-bottom flask and stirred at 40°. A solution of ethyldiazoacetate (2.64 ml, 4.0 eq.) in toluene (13 ml) is added dropwise (Caution) and the solution is left to react overnight. The solution is concentrated to dryness by rotary evaporation. The reaction flask is placed on an ice bath and a solution of 10% aq. HO Ac (50 ml) is added to the crude product. The mixture is adsorbed onto silica gel, and the product is purified by column chromatography [silica gel, EtOAc-Hex (1 9)]. 

In CHEC-II(1996), carbene insertion reactions into the N-H bond to form a fused-ring azetidinone warranted a separate section. In the last decade, the popularity to this approach to bicyclic systems seems to have markedly declined. Nevertheless, dirhodium tetraacetate and rhodium octanoate were used to generate the corresponding bicyclic compounds from the diazo compounds 241 (R2 = H and /3-Me), respectively, via the carbene intermediates. In the latter case, the produced enol was esterified and then the ester group replaced with a hydroxymethyl substituent to give derivatives 242 in a one-pot process <2001JCM166, 1999TL427>. 

Rhodium tetraacetate, as catalyst, in O-alkylation 666 Rhodococcus 978 Ring current effects 336 Ring inversion, cone-to-cone 1385, 1386 Ring-walk isomerization 283 Ripening, state of, effect on organoleptic properties of foodstuffs 913 River water, analysis of 946, 947, 962, 977 Road particulate matter, phenoUc compounds in 938... 

Without the disadvantage of using diazo compounds in the first step, Wenkert s latest monoterpenoid syntheses would be most efficient approaches, and in any case represent novel routes to well-known materials. Nezukone (754) was the result of examining the reaction between butadiene and diazopyruvic ester catalyzed by rhodium tetraacetate. The major product of the addition was the cyclopropane 758 (Scheme 62). It was known that divinylcyclopropanes could be thermolyzed to cycloheptadienes (Vol.4, p.537, Ref.600). The Wittig product from 758 thus gives a cycloheptadiene, and subsequent steps are shown in the scheme. The last step involves Grignard addition to the ester function of the enolate, then loss of water and redistribution of the double bonds.(Further examples of the use of diazo compounds will be found under perillene in the section on furans.)... 

A highly stereoselective synthesis of alkyl vinylcyclopropane carboxylates has also been reported21. Using rhodium(II) tetraacetate, several alkenyl-substituted diazoacetates transfer their carbene unit to monosubsliluled olefins with good efficiency. 

Rhodium(ll)-catalyzed decomposition of vinyldiazomethanes in dichloromethane in the presence of dirhodium(II) tetraacetate has found wide application in the construction of seven-membered rings828,829,854. Several methods for the synthesis of the required vinyldiazomethanes are available, for example, diazo transfer from 4-acetamidobenzenesulfonyl azide in the presence of a base (triethylamine for 17, or l,8-diazabicyclo[5.4.0]undec-7-ene for less acidic precursors, e.g., 21, p 3580) to a C-H acidic compound824, 829 8=5"859 e.g., the formation of 19824. 

A convenient route to polysubstituted oxazoles was developed through a variation on the Robinson-Gabriel synthesis in which the key 1,4-dicarbonyl compounds were obtained by a rhodium carbene N-H insertion reaction. Dirhodium tetraacetate catalysed reaction of primary amides 103 and diazocarbonyl compounds 107 gave a-acylaminoketones 108, which were converted into 109 by cyclodehydration using the Wipf and Miller protocol <04T3967>. 

Taber and co-workers also showed that diazocarbonyls undergo C—H insertion reactions in the presence of rhodium acetate [Rh2(OAc)4].3i0b,3ll jaber and Schuchardt used this method for the conversion of 393 to 394 (91% yield) in a synthesis of ( )-pentalenolactone E methyl ester. a-Cuparenone was also synthesized by this method.313 Undheim used this approach for the synthesis of p-oxaspirane systems.3i4 When 395 was treated with a catalytic amount of rhodium tetraacetate, for example, spiro diketone 396 was obtained in 43% yield. 

A very impressive comparison of yields in cyclopropanations of a large number of alkenes with methyl and ethyl diazoacetate under identical reaction conditions, but with three different catalysts, namely copper(ii) triflate, palladium(ii) diacetate, and dirhodium(ii) tetraacetate, was made by Anciaux et al. (1980). They demonstrated that the rhodium catalyst gives the highest yield in 17 out of 20 cases the palladium catalyst is better in three cases, and copper triflate is lower, except in one case in which it equals the result with the rhodium catalyst. 

Oxazolin-2-ones 88 are formed when a-hydroxyamides 85) (R, R = alkyl or aiyl) are treated with the cumulated phosphorus ylide 86. The reactions are thought to proceed via the intermediates 87 <97LA217>. The diazomalonylurea derivative 89 is converted into the betaine 91 in the presence of a catalytic amount of dirhodium tetraacetate, presumably by way of the rhodium complex 90 (L = ligand). The betaine reaiTanges to the isomiinchnone 92, which reacts... 

Other syntheses of 33 have been presented in more recent years Weeratunga et al. presented a nine-step-synthesis with 4% overall yield (45), where the key steps were a cycUzation-deiodination-reaction and a lead tetraacetate-conducted ring closure. Koreeda et al. published their building-block-synthesis in 1993 with 11% overall yield (46), and in 1996, Pirrung and Lee synthesized 33 via a rhodium carbenoid dipolar cycloaddition (47). 

Thus, exposure of diazoamide (14) to rhodium(II) tetraacetate gave a 72% yield of y-lactam (15) and the corresponding -lactam was not detected. 

Related Reagents. Acrylonitrile boron trifluoride etherate ceric(rV) ammonium nitrate 2,3-dichloro-5,6-dicyano-/7-benzo-quinone drrhodium(II) tetrakis[methyl 4(/J)-2-oxazolidinone-4-carboxylate] drrhodium(II) tetrakis[(5)-Ai-phthaloyl-r-leucinate] DMSO epichlorohydrin lithium aluminum hydride methyl acrylate methyl lithium methyl triflate tetrabuty-lammonium fluoride trimethylsilyl chloride rhodium(II) tetraacetate. 

Candeias and coworkers have employed a-diazoamides 23 in the presence of dirhodium tetraacetate for the synthesis of 2-azetidinones 24 containing an acyl, sulfonate, and phosphonate groups on C-3 in aqueous medium (Scheme 7) [36]. The reaction has been explained by intramolecular C-H insertion of rhodium carbenoids. The study... 

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