Rhodium diacetate

The catalytic activity of rhodium diacetate compounds in the decomposition of diazo compounds was discovered by Teyssie in 1973 [12] for a reaction of ethyl diazoacetate with water, alcohols, and weak acids to give the carbene inserted alcohol, ether, or ester product. This was soon followed by cyclopropanation. Rhodium(II) acetates form stable dimeric complexes containing four bridging carboxylates and a rhodium-rhodium bond (Figure 17.8). 

The rhodium diacetate dimer is used in catalytic amounts 0.132% (weight of dimer/weight of diazo ketone) has worked out to be the best ratio for this reaction. 

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

Diphenyl-1-sila-cyclohexan-4-one, prepared from divinyldiphenylsilane, is converted into 1,1-diphenyl-l-silacycloheptan-4-one, first by treatment with ethyl diazoacetate and LDA at -78 °C then rhodium diacetate at room temperature <95SLt i t>. 

It has been reported that the glycal 348 undergoes cyclopropanation to give 349 or 350 as the major products, depending on the choice of reagent [99]. Treatment of 348 with ethyl diazoacetate in the presence of rhodium diacetate gave a 59% yield... 

Boc-D-tyrosine in five steps, which included p-tetralone formation by rhodium diacetate-catalyzed C—H insertion of the diazo compound 65. Then, treatment of 66 with methyl iodide under the influence of PTC 2(12 mol%) in toluene/ 50% aqueous KOH solution led to the production of the desired (lS,4/ )-isomer of 67 in 90% yield with a diastereo-meric ratio of 12 1 (based on isolated yield). After the removal of acid-sensitive protective groups and the... 

The reaction mechanism and rates of methyl acetate carbonylation are not fully understood. In the nickel-cataly2ed reaction, rate constants for formation of methyl acetate from methanol, formation of dimethyl ether, and carbonylation of dimethyl ether have been reported, as well as their sensitivity to partial pressure of the reactants (32). For the rhodium chloride [10049-07-7] cataly2ed reaction, methyl acetate carbonylation is considered to go through formation of ethyUdene diacetate (33) ... 

Acetyl chlotide is reduced by vatious organometaUic compounds, eg, LiAlH (18). / fZ-Butyl alcohol lessens the activity of LiAlH to form lithium tti-/-butoxyalumium hydtide [17476-04-9] C22H2gA102Li, which can convert acetyl chlotide to acetaldehyde [75-07-0] (19). Triphenyl tin hydtide also reduces acetyl chlotide (20). Acetyl chlotide in the presence of Pt(II) or Rh(I) complexes, can cleave tetrahydrofuran [109-99-9] C HgO, to form chlorobutyl acetate [13398-04-4] in about 72% yield (21). Although catalytic hydrogenation of acetyl chlotide in the Rosenmund reaction is not very satisfactory, it is catalyticaHy possible to reduce acetic anhydride to ethylidene diacetate [542-10-9] in the presence of acetyl chlotide over palladium complexes (22). Rhodium trichloride, methyl iodide, and ttiphenylphosphine combine into a complex that is active in reducing acetyl chlotide (23). 

An early attempt to hydroformylate butenediol using a cobalt carbonyl catalyst gave tetrahydro-2-furanmethanol (95), presumably by aHybc rearrangement to 3-butene-l,2-diol before hydroformylation. Later, hydroformylation of butenediol diacetate with a rhodium complex as catalyst gave the acetate of 3-formyl-3-buten-l-ol (96). Hydrogenation in such a system gave 2-methyl-1,4-butanediol (97). 

Alternatively, butadiene can be oxidized in the presence of acetic acid to produce butenediol diacetate, a precursor to butanediol. The latter process has been commercialized (102—104). This reaction is performed in the Hquid phase at 80°C with a Pd—Te—C catalyst. A different catalyst system based on PdCl2(NCCgH )2 has been reported (105). Copper- (106) and rhodium- (107) based catalysts have also been studied. 

In addition to conventional generation of carbenes from nitrodiazo compounds (22) (79), target intermediates C can be prepared by oxidation of functionalized AN CH2XNO2 with phenyliodonium diacetate. The reactions of Rhodium intermediates with certain olefins afford the corresponding cyclopropanes (23). The cycloaddition reaction was performed in the presence of a catalyst. (The successful synthesis of nitrocyclopropanes from trinitromethane derivatives and nitroacetic ester was also documented (81)). 

The single step conversion of methyl acetate to ethylidene diacetate is catalyzed by either a palladium or rhodium compound, a source of iodide, and a promoter. The mechanism is described as involving the concurrent generation of acetaldehyde and acetic anhydride which subsequently react to form ethylidene diacetate. An alternative to this scheme involves independent generation of acetaldehyde by reductive carbonylation of methanol or methyl acetate, or by acetic anhydride reduction. The acetaldehyde is then reacted with anhydride in a separate step. 

Reductive Carbonylation of Methanol. As discussed earlier, rhodium based catalysts are capable of catalyzing the reductive carbonylation of methyl acetate to ethylidene diacetate ( 1), as well as the carbonylation of methyl acetate to acetic anhydride (16). These reaction proceed only, wjjen, tjie reaction environment... 

Intramolecular carbene insertion into the O-H bond (Equation 11), which proceeds after the treatment of diethyl 6-hydroxy-2-oxo-l-diazoalkylphosphonates with rhodium(ll) diacetate, leads to the respective oxepanes <1994J(P1)501>. 

Sulfamate indan-2-yl ester 145 is oxidized by iodobenzene diacetate to give condensed 1,2,3-oxathiazole di-A-oxides 146 (Equation 35). Various rhodium <2001JA6935, 2004HCA1607>, manganese(m) Schiff base <2005TL5403>, and ruthenium porphyrin <2002AGE3465> catalysts can be used for this transformation. Enantioselective intramolecular amidation is achieved with good yields. 

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... 

Starting from butenediol acetate (28), a further carbon atom is introduced by rhodium-catalyzed hydroformylation, likewise after a copper-catalyzed allyl rearrangement to give vinylglycol diacetate. Splitting of an acetyl group leads to the P-formylcrotyl acetate (8 b) (C5 acetate) 34 a). 

In the BASF process the 1,2-diacetate is the substrate for the hydroformylation step. It can be prepared either directly via oxidative acetoxylation of butadiene using a selenium catalyst or via PtCl4-catalyzed isomerization of the 1,4-diacetate (see above). The latter reaction affords the 1,2-diacetate in 95% yield. The hydroformylation step is carried out with a rhodium catalyst without phosphine ligands since the branched aldehyde is the desired product (phosphine ligands promote the formation of linear aldehydes). Relatively high pressures and temperatures are used and the desired branched aldehyde predominates. The product mixture is then treated with sodium acetate in acetic acid to effect selective elimination of acetic acid from the branched aldehyde, giving the desired C5 aldehyde. 

Even with added iodide salt formation of the inactive [Rh(CO)2l4] can be a problem, since under anhydrous conditions this Rh(III) species cannot be reduced to the active [Rh(CO)2l2] by reaction with water. In the Eastman process, this problem is addressed by addition to the CO gas feed of some H2 which can reduce [Rh(CO)2l4] by the reverse of Equation 8. However, the added H2 does lead to some undesired by-products, particularly ethylidene diacetate (1,1-diacetoxyethane) which probably arises from the reaction of acetic anhydride with acetaldehyde (Equation 19 from hydrogenolysis of a rhodium acetyl) ... 

The ligand was then used to form a variety of transition metal carbene complexes [207] (see Figure 3.72). Interestingly, more than one method for the formation of transition metal carbene complexes was successfully employed presence of an inorganic base (IC COj) to deprotonate the imidazolium salt and the silver(I) oxide method with subsequent carbene transfer to rhodium(I), iridium(I) and copperfi), respectively. The silver(I) and copper(I) carbene complexes were used for the cyclopropanation of styrene and indene with 1,1-ethanediol diacetate (EDA) giving very poor conversion with silver (< 5%) and qnantitative yields with copper. The diastereomeric ratio (endolexo) was more favonrable with silver than with copper giving almost a pnre diastereomer for the silver catalysed reaction of indene. 

It takes place in the liquid phase around 130 to 160 G and between 4 and 7.10 Pa absolute, in the presence of a catalyst complex based onpaHadium or rhodium, methyl iodide, and an amine or phosphine as initiator. Acetic anhydride ts formed as an intermediate. The convefston is directed toward the production of etfaytidene diacetate by increasing the proportionof CO in the synthesis gas. 

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