Silver -catalyzed reaction

Silver Catalyst Process. In early formaldehyde plants methanol was oxidized over a copper catalyst, but this has been almost completely replaced with silver (75). The silver-catalyzed reactions occur at essentially atmospheric pressure and 600 to 650°C (76) and can be represented by two simultaneous reactions ... 

For the bicarbonate reaction, gently mix for 20 hours at 4°C. For the silver-catalyzed reaction, continue the reaction for 1 hour or until the silver complex has fully dissolved. 

Kinetic experiments have been performed on a copper-catalyzed substitution reaction of an alkyl halide, and the reaction rate was found to be first order in the copper salt, the halide, and the Grignard reagent [121]. This was not the case for a silver-catalyzed substitution reaction with a primary bromide, in which the reaction was found to be zero order in Grignard reagents [122]. A radical mechanism might be operative in the case of the silver-catalyzed reaction, whereas a nucleophilic substitution mechanism is suggested in the copper-catalyzed reaction [122]. The same behavior was also observed in the stoichiometric conjugate addition (Sect. 10.2.1) [30]. 

The autoacceleration of the silver-catalyzed reaction in the early stages is greater than would be expected from a simple increase in catalyst surface by growth of the silver nuclei orginally present. Apparently new nuclei are readily formed during the reaction. A possible mechanism which could lead to this result is ... 

A reactive intermediate may be responsible for the copper catalysis of the hydroxylamine reaction. The intermediate formed in the silver-catalyzed reaction, if it has any real existence, is not further oxidized but breaks down into nitrogen and water. Oxidation of hydroxylamine by cupric ion, on the other hand, yields predominately nitrous oxide. The intermediate formed by the removal of a single electron from the hydroxylamine in this reaction must be further oxidized to yield the final product. Such an intermediate may react readily with silver ions in solution. 

Similar results were obtained by Dake et al. with silver catalyzed reactions, showing that the thermal stability of gold was higher than silver but silver catalyzed reactions were faster [138]. 

Several compensation effects have been reported for the decomposition of formic acid on metals (231) particular interest has been shown in the silver-catalyzed reaction (19, 35, 232, 233). The available data for this rate process do not, however, define a single compensation relation, and, even for groups of closely related reactions, it is difficult to decide which of the various possible calculated lines provides the most meaningful representation of the kinetic measurements. Values of B and e, obtained from various sets of reported results, extend over a significant range and, moreover, there is an apparent tendency for an increase in the value of one of these parameters to be offset by a diminution in the other. Such behavior can, in the widest sense of the word, be described as compensatory. To illustrate the difficulties inherent in this analysis of the published data, some calculated values of B and e derived from possible alternative groups of observations are discussed here. Values of (log A, E) reported by Sosnovsky (35), for the decomposition of formic acid on silver, may be considered either as the three different lines, Table III, K, L, and M for reactions on the (111), (110), and (100) planes, respectively, or as the single line,Table III, N. These combined data (Table III, N and x on Fig. 6) intersect with the line obtained from a different set of results... 

Preparation of highly substituted furans was reported by tandem ring-opening/cyclization reactions of alkynyl epoxy alcohols in moderate to good yields using alcohol as a nucleophile and Cu(OTf)2 as catalyst, as can be seen below <07S3295>. Silver-catalyzed reaction of similar substrates, 3-alkyne-l,2-diols, also furnished the corresponding... 

Paquette et al., examining the same silver-catalyzed reaction as Masa-mune, reported similar stereospecificity A kinetic study of this reaction further established the reversible intervention of a silver-bicyclobutane complex. The kinetic data did not bear on the nature of the complex. The reported equilibrium constant (K =0.19 0-09), however, revealed that the extent of complex formation was substantial. 

The silver-catalyzed reactions of bicyclobutanea were thoroughly studied by Paquette s group. They showed that in some cases, the reaction sequence involves first cleavage of a side bond to form an argentocarbocation, which is then followed by a skeletal rearrangement " . Two examples are shown below (equations 114 and 115). (For the last... 

Yet another case where a bridged compound (33) is obtained rather than the propellane was found when benzocyclopropene (32) reacted with butadiene in a silver-catalyzed reaction This is a case where the sextet of electrons suffices for stabilizing the open... 

A silver-catalyzed reaction of methyl ortfoi-fiarmylphenylpropargylate with alkenes led to a tandem 1,3-dipolar cycloaddition/cyclopropanation producing a series of polycyclic compounds with tetrahydrofuran moieties (140L4412). 

Ketenes generated in situ by dehydrochlorination react with isoqui-noline-N-oxides generated in situ from silver catalyzed reaction of 2-alkynylbenzaldoximes, and give an initial [3 -f- 2] cycloaddition followed by rearrangement to 161 and then to the product 162 (Eqn (4.101)). ° ... 

Silver-catalyzed reactions of benzocyclopropene with various unsaturated hydrocarbons gave coupling products (Table 2.6). 

Scheme 5.128 Enantioselective silver-catalyzed reaction of tin enolates 518 with nitrosobenzene 515 to a-aminooxy ketones 519 as intermediates for the formation of...

The silver-catalyzed reaction of 2-allqmylbenzaldoximes with secondaiy phosphine oxides led eventually to 1-phosphinoyl-isoquinolines after tandem addition, cyclization and dehydration steps (Scheme 35)/ ... 

Scheme 3-196. Silver-catalyzed reaction of stannyl enol ethers with nitroso...

Naodovic M, Yamamoto H. Asymmetric silver-catalyzed reactions. Chem. Rev. 2008 108 3132-3148. 

Kochi JK, Tamura M. Mechanism of the silver-catalyzed reaction of Grignard reagents with alkyl halides. J. Am. Chem. Soc. 1971 93(6) 1483-1485. 

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