Copper carboxylate, decomposition, metal

Transition-metal catalyzed decomposition of alkyl diazoacetates in the presence of acetylenes offers direct access to cyclopropene carboxylates 224 in some cases, the bicyclobutane derivatives 225 were isolated as minor by-products. It seems justified to state that the traditional copper catalysts have been superseded meanwhile by Rh2(OAc)4, because of higher yields and milder reaction conditions217,218) (Table 17). [(n3-C3H5)PdCl]2 has been shown to promote cyclopropenation of 2-butyne with ethyl diazoacetate under very mild conditions, too 2l9), but obviously, this variant did not achieve general usage. Moreover, Rh2(OAc)4 proved to be the much more efficient catalyst in this special case (see Table 17). 

The reaction, formally speaking a [3 + 2] cycloaddition between the aldehyde and a ketocarbene, resembles the dihydrofuran formation from 57 a or similar a-diazoketones and alkenes (see Sect. 2.3.1). For that reaction type, 2-diazo-l,3-dicarbonyl compounds and ethyl diazopyruvate 56 were found to be suited equally well. This similarity pertains also to the reactivity towards carbonyl functions 1,3-dioxole-4-carboxylates are also obtained by copper chelate catalyzed decomposition of 56 in the presence of aliphatic and aromatic aldehydes as well as enolizable ketones 276). No such products were reported for the catalyzed decomposition of ethyl diazoacetate in the presence of the same ketones 271,272). The reasons for the different reactivity of ethoxycarbonylcarbene and a-ketocarbenes (or the respective metal carbenes) have only been speculated upon so far 276). 

Because of the high nucleophilicity and reactivity of diazoalkanes, catalytic decomposition occurs readily, not only with a wide range of transition metal complexes but also with Brpnsted or Lewis acids. Well-established catalysts for diazodecomposition include zinc halides [638,639], palladium(II) acetate [640-642], rhodium(II) carboxylates [626,643] and copper(I) triflate [636]. Copper(II)... 

This mechanism is of importance in radical induced amino acid damage catalyzed by copper ions. The study of the decomposition of transients with a metal-carbon -bond containing two potential leaving groups (both an amine and a carboxylate group) at the p position of the carbon centered radical is of special interest. It was reported that the intermediate formed with the amino acid 2-methylalanine with cupric ions decomposes via p-carboxyl elimination whereas the intermediate formed with cuprous ions decomposes via p-amine elimination (102). 

Broadbent et al. [69] showed that ar-time curves for the decomposition of copper(II) oxalate (503 to 533 K) were sigmoidal and that data for the vacuum reaction fitted the Avrami-Erofeev equation with values of = 2.9 initially and later n = 3.5 ( , = 136 kJ mol ). Electron transfer was identified as the step controlling the reaction. There was no evidence from X-ray diffraction studies for the intervention of the Cu salt the orthorhombic structure was present until disappearance of the reactant and product copper metal was detected. However, many metal carboxylates, chilled after dehydration, yield anhydrous salts that are amorphous to X-rays or poorly crystalline, see, for example [70]. 

Allyldiethylamine behaves similarly, but the yields are low since neither the starting amine nor the products are stable to the reaction conditions. For the efficiency of the cyclopropanation of the allylic systems under discussion, a comparison can be made between the triplet-sensitized photochemical reaction and the process carried out in the presence of copper or rhodium catalysts whereas with allyl halides and allyl ethers, the transition metal catalyzed reaction often produces higher yields (especially if tetraacetatodirhodium is used), the photochemical variant is the method of choice for allyl sulfides. The catalysts react with allyl sulfides (and with allyl selenides and allylamines, for that matter) exclusively via the ylide pathway (see Section 1.2.1.2.4.2.6.3.3. and Houben-Weyl, Vol. E19b, pll30). It should also be noted that the purely thermal decomposition of dimethyl diazomalonate in allyl sulfides produces no cyclopropane, but only the ylide-derived product in high yield.Very few cyclopropanes have been synthesized by photolysis of other diazocarbonyl compounds than a-diazo esters and a-diazo ketones, although this should not be impossible in several cases (e.g. a-diazo aldehydes, a-diazocarboxamides). Irradiation of a-diazo-a-(4-nitrophenyl)acetic acid in a mixture of 2-methylbut-2-ene and methanol gave mainly l-(4-nitrophenyl)-2,2,3-trimethylcyclo-propane-1-carboxylic acid (19, 71%) in addition to some O-H insertion product (10%). ... 

Transition-metal catalyzed decomposition of alkyl diazoacetates in the presence of acetylenes offers direct access to cyclopropene carboxylates 224 in some cases, the bicyclobutane derivatives 225 were isolated as minor by-products. It seems justified to state that the traditional copper catalysts have been superseded meanwhile by RhjCOAc), because of higher yields and milder reaction conditions (Table 17). 

The above example demonstrates the manner in which a study of model nonenzymatic reactions can elucidate enzymatic reactions. Another example of such a model reaction that has been studied is the decomposition of 6-succinoaminopurine and its derivatives in the presence of metal ions (8). The results of this study indicated that a side-chain carboxyl group is essential for the reaction, and that in the a-position it was much more effective than in the jS-position. Therefore a metal chelate intermediate for the reaction was postulated in which cleavage of the C—N bond could occur quite readily to give adenine, a product which was identified, and fumaric acid. The latter compound was not identified but is obtained in analogous enzymatic reactions involving adenylsuccinic acid. The most effective metal ions were copper(II) and manganese(II), although protons in the absence of metal ions were also able to carry out this reaction at a slow but measurable rate. 

The use of cobalt and manganese carboxylates to initiate the oxidation of a large number of olefins such as the butenes [447, 448], propylene [449], oleic [450] linoleic [451], and stearic [452, 453] acids or their derivatives and a-methylstyrene [454, 455] is well known. The kinetics of oxidation of a-methylstyrene in the presence of cobaltous and manganous acetylacetonates as well as copper phthalocy-anine have been investigated [454, 455]. The results of this study led Kamiya to postulate a mechanism involving formation of radical species by a metal dioxygen complex, equation (270), concurrent with radical generation by hydroperoxide decomposition. 

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