Dirhodium tetraacetate

Decomposition of the diazo ester 395 in presence of dirhodium tetraacetate gives the zwitterionic intermediate 396, which undergoes a 1,3-dipolar cycloaddition with the double bond of the adjacent vinylindole. The bridged compound is isolated in good yield when the reaction is carried out at room temperature however, at 50 °C or above, compound 397 is the only compound isolated, again in good yield (Scheme 93) <2005JOC2206>. 

The matter was settled in 1994 in back-to-back communications by Gould [12] and Dmitrienko [13]. Gould showed that treatment of natural prekinamycin with dirhodium tetraacetate in methanol yielded the fluorene 16 (Scheme 3.1). The vinyl proton formed in this reaction (H-l) provided a critical spectroscopic handle and allowed unambiguous determination of the carbocyclic structure, excluding the presence of an indole heterocycle. In parallel, his research group obtained a high-quality crystal structure of a kinamycin derivative. The refined data set was shown to best accommodate a diazo rather than cyanamide (or isonitrile) function. 

Ferreira developed a novel method for the preparation of masked 1,4-dicarbonyl derivatives for utilization in the Paal-Knorr synthesis of pyrroles <00SC3215>. In this process, the reaction between diazocompound 3 and n-butyl vinyl ether using dirhodium tetraacetate as catalyst provides dihydrofurans 4 which are easily converted into substituted... 

The size of the silyl groups in compounds R3SiC(N2)COOMe influences their decomposition by copper triflate, dirhodium tetraacetate and dirhodium... 

For the transition-metal catalyzed decomposition of silyl-substituted diazoacetates 205 [silyl = SiMe3, SiEt3, SiMeiBu-i, SitPr-i SiPtnBiW, SiMe2SiMe3], copper triflate and dirhodium tetrakis(perfluorobutyrate) proved to be the best catalysts114. While these two catalysts induce the elimination of N2 at 20 °C even with bulky silyl substituents, dirhodium-tetraacetate even at 100 °C decomposes only the trimethylsilyl-and triethylsilyl-diazoacetates. When the decomposition reactions are carried out in... 

The formation of aziridines using bromamine-T was catalysed by cobalt porphyrins.77 Yields range from the mid-50% level to >90% with aliphatic and aromatic alkenes. Sulfonimidamide also yielded aziridines when treated with iodosylbenzene diacetate in the presence of dirhodium tetraacetate.78... 

The 1,3-dipolar cycloaddition of the carbonyl ylide (31) to the aldimine (32) produces the adduct (33), which has been used to synthesize the taxol C(13) side-chain (34), which is known to be required for the antitumour activity of taxol (Scheme 9).35 The dirhodium tetraacetate-catalysed decomposition of l-diazo-5-phenylpentane-2,5-dione (35) yields the carbonyl ylide (36), which cycloadds to methylenecyclopropanes (37) to produce spirocyclopropanated 8-oxabicyclo[3.2.1]octan-2-ones [(38)-(40)] in 6-75% yields (Scheme 10).36 The 1,3-dipolar cycloadditions of aliphatic or alicyclic thiocarbonyl ylides with thiobenzophenone produce both regioisomeric 1,3-dithiolanes as expected. However, in the case of highly sterically hindered thiocarbonyl ylides, methylene transfer leads to the formation of 4,4,5,5-tetraphenyl-l,3-dithiolane.37,38... 

The reaction of 2,3-diphenylazirine 613 with diazomalonate 614 in the presence of dirhodium tetraacetate afforded 2,3-diphenylazetine-4,4-dicarboxylate 615, the structure of which was acknowledged through reduction toward azetidine 616 and hydrolysis toward /3-amino ketone 617 (Scheme 82) <2004TL6003>. 

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>. 

An important paper describes the formation of the metal-metal bonded dirhodium tetracarboxylate trifluorophosphine complex [Rh2(OCOCH3)4(PF3)2] made directly from the dirhodium tetraacetate complex by direct addition of PF3 to the formally metal-metal triple bond. The structure was determined by a single-crystal X-ray study, and has been compared with other [Rh2(OAc)4X2] systems (X = py, Et2NH, CO, and P(OR)3). 

Ceccherelli, P., Curini, M., Marcotullio, M. C., Rosati, O. Dirhodium tetraacetate-catalyzed decomposition of 3,Y-unsaturated diazo ketones a new entry to vinylogous Wolff rearrangement. Gazz. Chim. Ital. 1994,124,177-179. 

Arylcyclopropanes can be prepared from a variety of alkenes enamines react sluggishly, electron-rich alkenes are, in general, the most reactive. Thus, phenylcarbene, generated by dirhodium tetraacetate catalyzed decomposition of phenyldiazomethane, gave 2-butyl-1-phenyl-cyclopropane (2) in 6% yield from hex-l-ene, but l-butoxy-2-phenylcyclopropane (3) was obtained in 92% yield from butyl vinyl ether. ... 

Cyclopropanation of dienes 90 or 94 with 3,3-dichlorodiazopropene (91b) or the parent diazo compound 91 a (X = h) in the presence of dirhodium tetraacetate leads to a mixture of the rearranged fused eyeloheptadienes 93 and 96 and the stable tra .v-l,2-divinylcyclopropanes 92 and 95. The trans- 1,2-divinyl derivatives can be transformed to the seven-meinbered ring by heating to 110 °C854. 

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>. 

Honda and his co-workers synthesised methyl (+)-nonactate 179, setting up the C-6 to C-8 relationship by a chelation controlled allylsilane reaction on the aldehyde 169, and the C-3 centre by hydrogenation of the dehydro intermediate 176 carrying two methoxycarbonyl groups (37) (Scheme 24). The thiolactone 175 and dimethyl diazomalonate gave the dehydro intermediate 176 in the presence of dirhodium tetraacetate, by way of a sulfur-ylid rearrangement developed by these... 

Intramolecular carbenoid insertion into NH bonds of diazohydrazides of type 8.142 is also possible, as shown by Lawton et al. (1987). In boiling benzene, diazetidine-l,2-diones (8.143) are obtained in good yield (87-93 <7o), if dirhodium tetraacetate is used as catalyst (8-61). 

ChiralcarboxamMatecomplexes. After exchanging the ligands of dirhodium tetraacetate to chiral pyrrolidinones (as well as their heteroatom analogs) bearing a methyl ester at C-5 new carboxamidate complexes are formed. These are catalysts of choice for enantioselective intramolecular metal carbene transformations. One such complex is particularly effective for the formation of P-benzyl-y-butyrolactones from hydrocinnamyl diazoacetates. The lactones are useful for the synthesis of some lignans. 

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... 

Treatment of benzyl dimethyl amine with the diazo carbonyl compoimd 19 in the presence of a catalytic amount of copper afforded a-trifluoromethyl phenylalanine 20 via a [1,2]-Stevens rearrangement. The reaction time was reduced significantly to 1-2 h when dirhodium tetraacetate was used as catalyst. 

The diazo ketone 31 upon treatment with dirhodium tetraacetate underwent Stevens rearrangement resulting in a mixture of decalone 32 and a ketone 33. It has been found that the yield of 32 is increased in the absence of a nucleophile. The formation of 32 as major product indicated that the reaction proceeds through the key intermediate 34 that possesses a less-strained bicyclic structure. 

The synthesis and characterization of dirhodium tetraacetate in the 1960s introduced a new era for metal-metal bonded compounds due to their diverse array of applications as catalysts [37-39], photocatalysts [40 -43], peptide-modifying agents and metallopeptide catalysts [44-51], DNA and RNA nucleobase-modification catalysts [52], metallo-pharmaceuticals [53-56], photodynamic therapy agents [57], building blocks for the design of supramolecular architectures [58], and others. In this respect, many new Rh2(II,II) systems displaying unique properties have been reported in recent years. 

Recently, Francis etal. reported the selective modification of tryptophan indole side chains in several proteins with a diazo reagent catalyzed by dirhodium tetraacetate [44], and Ball etal. achieved remarkable rate accelerations for tryptophan modification (>10 ) using dirhodium metallopeptides (Section 9.3.2) [45]. 

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