Cupric acetate, reaction with

Figure 16 also shows that the concentration of cupric acetate remained constant as long as dichromate was undergoing reaction. Only when the reduction of dichromate was complete did the cupric acetate react with hydrogen to form cuprous oxide. Apparently the reduction of cupric acetate is not affected by the previous dichromate reaction or by the presence of small amounts of chromic salts in the solution. 

The rate of the catalyzed dichromate reaction was measured at temperatures ranging from 80° to 140°. The results were found to give a good Arrhenius plot. The activation energy is 24.6 kcal./mole, in close agreement with the value of 24.2 kcal./mole found for the reaction of cupric acetate itself with hydrogen. 

The details of the cupric salt reaction with the palladium adduct are not clear. Exchange to form a cupric alkyl is one possibility or complex formation,"probably with chloride bridges between the palladium adduct and cupric chloride, may occur with subsequent anion shift from palladium to carbon or perhaps an Sn2 displacement of the complex metal group by an anion may occur. Rearrangements producing 1,3 and 1,4 substituted products from linear olefins have also been observed. For example, 1-butene produced several percent of 1,3- and 1,4-chloro acetates and diacetates under the reaction conditions used 16>. "Hydrido-palladium acetate or chloride" -complexes would seem to be likely intermediates in these arrangements. 

Oxygenation. Brackman et al.1 found that cupric acetate complexed with an amine (pyridine was used) in the presence of abase such as triethylamine functions as a homogeneous catalyst in methanol for the air oxidation of A5-cholestenone to A4-cholestene-3,6-dione in 75% yield. The reaction is applicable to a,fi- and fi.y-aldehydes and ketones for example ... 

Routes via o-aminophenylpyrroles present the most convenient syntheses of a wide variety of pyrrolo[l,2-a]quinoxalines. Thus reaction of the amino compound 6 with acetic anhydride in acetic acid gave the acetamido derivative which was cyclized with phosphoryl chloride to give the 4-methyl compound 7 (R = Me) in 56% yield. The 4-phenyl compound 7 (R = Ph) has been prepared similarly. An even more convenient synthesis of 4-aryl compounds is achieved by reaction of compound 6 with aromatic aldehydes to give the 4,5-dihydro derivatives These are readily oxidized to 4-arylpyrrolo[l,2-a]quinoxalines 9 with manganese dioxide. This approach may be carried out in one step by reaction of compound 6 with aromatic aldehydes (e.g., benzaldehyde) in the presence of cupric acetate. Reaction of the aminophenylpyrrole 6 with 90% formic acid gave pyrrolo[l,2-a]quinoxaline (7, R = H) directly in 98% yield. Pyrrolo[l,2-a]quinoxalines substituted in the l-position and the 7-position have also been prepared from appropriately substituted... 

AU these authors proposed that the mechanism bears some similarity to the copper-mediated arylation of amines from triarylbismuth compounds, described by Barton et al. [273]. Thus, the reaction would proceed via the formation of a cupric acetate complex with the nucleophile followed by a transmetallatimi with arylboronic acid playing the role of the triarylbismuth, before affording the N-arylated compound by reductive elimination. This last step would be facilitated by prior oxidation by dioxygene of a copper II intermediate to a copper IB intermediate [266-270, 274]. Some authors reported that the addition of molecular... 

A solution of bismuth trioxide in hot glacial acetic acid provides a specific method for the oxidation of acyloins. " The reaction rate is dependent on the steric accessibility of the ketol system. A 2,3-ketol requires less than one hour for completion but an 11,12-ketol is not yet fully oxidized in thirty hours." The reaction is highly selective as a-keto acids, hydrazines and phenols are not oxidized. In a direct comparison with cupric acetate, this procedure is somewhat superior for the preparation of a 2,3-diketone from a 2-keto-3-hydroxy steroid. ... 

A mixture of 800 g of potassium o-bromo-benzoate, 1,500 ml of bis-(2-methoxyethyl)ether, 355 g of N-ethyl-morpholine, 375 g of 2,3-dimethylaniline, and 30 g of cupric acetate is heated gradually with stirring to 140°C over a period of 90 minutes. The hot reaction mixture is then acidified with 260 ml of concentrated hydrochloric acid and the acidified mixture divided into 2 equal portions. One liter of water is added to each portion and the mixtures allowed to cool. The N-(2,3-dimethylphenyl)anthranllic acid which separates upon cooling is collected by filtration and recrystallized from bis(2-methoxyethyl)ether MP 229° to 230°C (corr.). 

The involvement of carbenes has been excluded in the DNA cleavage reactions activated by cupric acetate as these experiments were conducted in the dark. However, the contribution of metal-carbenoids [79] could not be ruled out. In a series of studies dealing with the metal-catalyzed... 

Oxidative addition consumes one equivalent of expensive Pd(OAc)2 in most cases. However, progress has been made towards the catalytic oxidative addition pathway. Knolker s group described one of the first oxidative cyclizations using catalytic Pd(OAc)2 in the synthesis of indoles [19]. They reoxidized Pd(0) to Pd(II) with cupric acetate similar to the Wacker reaction, making the reaction catalytic with respect to palladium [20]. 

Copper-catalyzed monoaddition of hydrogen cyanide to conjugated alkenes proceeded very conveniently with 1,3-butadiene, but not with its methyl-substituted derivatives. The most efficient catalytic system consisted of cupric bromide associated to trichloroacetic acid, in acetonitrile at 79 °C. Under these conditions, 1,3-butadiene was converted mainly to (Z )-l-cyano-2-butene, in 68% yield. A few percents of (Z)-l-cyano-2-butene and 3-cyano-1-butene (3% and 4%, respectively) were also observed. Polymerization of the olefinic products was almost absent. The very high regioselectivity in favor of 1,4-addition of hydrogen cyanide contrasted markedly with the very low regioselectivity of acetic acid addition (vide supra). Methyl substituents on 1,3-butadiene decreased significantly the efficiency of the reaction. With isoprene and piperylene, the mononitrile yields were reduced... 

A -Arylation of a wide range of NH substrates by reaction with boronic acid in the presence of cupric acetate and either triethylamine or pyridine at room temperature. The reaction works even for poorly nucleophilic substrates such as aryla-mide. 

Akermark et al. reported the palladium(II)-mediated intramolecular oxidative cyclization of diphenylamines 567 to carbazoles 568 (355). Many substituents are tolerated in this oxidative cyclization, which represents the best procedure for the cyclization of the diphenylamines to carbazole derivatives. However, stoichiometric amounts of palladium(II) acetate are required for the cyclization of diphenylamines containing electron-releasing or moderately electron-attracting substituents. For the cyclization of diphenylamines containing electron-attracting substituents an over-stoichiometric amount of palladium(II) acetate is required. Moreover, the cyclization is catalyzed by TFA or methanesulfonic acid (355). We demonstrated that this reaction becomes catalytic with palladium through a reoxidation of palladium(O) to palladium(II) using cupric acetate (10,544—547). Since then, several alternative palladium-catalyzed carbazole constructions have been reported (548-556) (Scheme 5.23). 

In terms of A -substitution, Hartwig reported improved conditions for the Pd(0) catalyzed N-arylation of indoles and pyrrole <99JOC5575>. It was found that when commercially available P(<-Bu)3 was employed as ligand and cesium carbonate as base, the reaction between indoles 95 and unhindered aryl bromides 96 or chlorides occurred under milder conditions than the Pd(OAc)2/DPPF system previously reported yielding the A/-arylated products 97. Alternatively, it has been found that pyrrole- and indole-2-carboxylic acid esters can be selectively 7V-arylated with phenylboronic acids in the presence of cupric acetate and either tiiethylamine or pyridine <99T12757>. 

In order to shorten the reaction time, various heavy metal salts (zinc, lead, and manganese acetates) of weak organic acids, zinc or cobalt and tin chlorides are added to the reaction mixture [11]. For example, refluxing an uncatalyzed mixture of 3 moles of isobutyl alcohol and urea for 150 hr at 108°-126°C gives a 49% yield of the carbamate. Adding lead acetate or cobalt chloride to the same reaction lowers the reaction time to 75 hr, at which point an 88-92 % yield is obtained. In another example, ethylene glycol (1 mole) and urea (2 moles) are heated for 3 hr at 135°-155°C with Mn(OAc)2 to give a 78% yield of the diurethane [11]. The commercial production of butyl carbamate uses catalytic quantities of cupric acetate [12]. 

Another important reaction of XXXIII and of XXXIV consists of their facile conversion to ferrocenyl acetate on treatment with cupric acetate. Ferrocenyl acetate in turn has been hydrolyzed to hydroxyferrocene, the ferrocene analog of phenol (74). 

A 250-mL, one-necked, round-bottomed flask is equipped with a magnetic stirrer and a reflux condenser protected by a calcium chloride drying tube. Into the flask are placed 30.0 g (0.14 mol) of di-tert-butyl malonate (Note 1) 8.4 g (0.28 mol) of paraformaldehdye (Note 2), 1.4 g (0.014 mol) of potassium acetate, 1.4 g (0.007 mol) of cupric acetate monohydrate, and 70 mL of glacial acetic acid. The resulting green-white suspension is placed in an oil bath preheated to 90-100°C and stirred for 2 hr (Note 3). The reaction mixture is allowed to cool to room temperature, and the reflux condenser is replaced with a short-path distillation apparatus, the vacuum outlet of which 1s connected in sequence to a trap cooled in acetone-dry ice, a potassium hydroxide trap, another trap cooled in acetone-dry ice, and a vacuum pump. The receiving flask 1s cooled in acetone-dry 1ce, and the system is evacuated over approximately 1 hr to remove acetic acid and other volatile material... 

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