Silver carboxylates synthesis

The reaction is likely to proceed by a radical-chain mechanism, involving intermediate formation of carboxyl radicals, as in the related Kolbe electrolytic synthesis. Initially the bromine reacts with the silver carboxylate 1 to give an acyl hypobromite species 3 together with insoluble silver bromide, which precipitates from the reaction mixture. The unstable acyl hypobromite decomposes by homolytic cleavage of the O-Br bond, to give a bromo radical and the carboxyl radical 4. The latter decomposes further to carbon dioxide and the alkyl radical 5, which subsequently reacts with hypobromite 3 to yield the alkyl bromide 2 and the new carboxyl radical 4Z... 

The Hunsdiecker reaction is a free-radical reaction for the synthesis of an alkyl halide. The starting material comes from the reaction of a silver carboxylate with a solution of a halogen in a solvent such as carbon tetrachloride (see Figure 12-44). The overall free-radical mechanism is shown in Figure 12-45. 

One particular radical decarboxylation reaction, which is used in the synthesis of alkyl or aryl bromide (Hunsdiecker reaction), involves reaction of the silver salt of a carboxylic acid with bromine, and results overall in loss of CO2 to form the corresponding alkyl or aryl bromide (Scheme 4.47). When silver carboxylate is treated with I2 ester formation occurs (Simonini reaction). 

Scheme 3.10 Synthesis of various sulfur-bridged silver clusters by reactions of silver carboxylates with silylated sulfur compounds in the presence of tertiary phosphanes.

This methodology is illustrated by the synthesis of platinum carboxylates through the reaction of platinum bromide complexes with silver carboxylates in dichloromethane, Scheme 5.1 ... 

Charan, S., Singh, N., Khanna, P.K. and Patil, K.R. (2006) Direct synthesis of nanocrystalline silver from the reaction between silver carboxylates and n-trioctylphosphine. Jourrud of Nanoscience and Nanotechnolcgy, 6, 2095-102. 

Isoquinoline reacts with aliphatic carboxylic acids photolyticaHy or with a silver catalyst to give excellent yields of alkylation products by decarboxylation (155). This method is useful in the synthesis of 2-benzoyhsoquinolines bearing a variety of aromatic substituents in the 1-position (156). 

In a modified procedure the free carboxylic acid is treated with a mixture of mercuric oxide and bromine in carbon tetrachloride the otherwise necessary purification of the silver salt is thereby avoided. This procedure has been used in the first synthesis of [1.1.1 ]propellane 10. Bicyclo[l.l.l]pentane-l,3-dicarboxylic acid 8 has been converted to the dibromide 9 by the modified Hunsdiecker reaction. Treatment of 9 with t-butyllithium then resulted in a debromination and formation of the central carbon-carbon bond thus generating the propellane 10." ... 

The aqua ion as a ligand is discussed in section 4.5. Silver forms a range of light-sensitive, insoluble carboxylates that find application in the synthesis of, for example, alkyl halides and esters. The benzoate, trifluoroacetate and perfluorobutyrate have dimeric structures others are polymers (Figure 4.6). 

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