Organosilvers

Other methods consist of the use of organosilver or organomercury aryl species, which have been used with 2,4,6-trinitrophenyl (Equation (28)),2113,21 4 polyhalophenyl,2115 or Mes derivatives (Equation (29)) 2116... 

The studies of structure and reactivity of organosilver radicals are significant to understand the mechanism of catalytic and biological processes. However, the radical reactions are very fast and in solution can be studied only by time-resolved techniques. Zeolites are well-suited for radical investigations because the reaction rates are much slower due to the sterical hindrances of the silicaalumina lattice. 

It was postulated that organosilver radicals were formed by reaction of CH2OH radicals with Ag+ cations. In order to solve a problem of organosilver radicals structure we carried out the experiments with 109Agi-NaA zeolite exposed to 13CH3OH. 

Stable organosilver(m) complexes having a general formula [Ag(GF3) X(4 )] with organic groups such as cyano, halo, methyl, alkynyl, difluoromethyl, and perfluoroethyl, replacing the trifluoromethyl groups in the [Ag(CF3)4] anion, as well as [Ag(CF3)3(NCMe)], were prepared. For instance, the air and moisture sensitive silver(i)... 

Allenic alcohols with a variety of allene substitution patterns form 2-alkenyltetrahydropyrans by a 6-exo ring closure upon cyclization with silver or mercury salts (equation 91 ).209 The organosilver intermediate undergoes protiodemetallation under the reaction conditions, while the vinylmercury... 

An alternative, but considered (192) a less likely possibility, was that Ru NO induced radical decomposition the case of an organosilver compound was cited as precedent (190). However, we note that in that work a nitroxide and not a spin trap was used. 

Kauffmann and coworkers have described the reaction of alkylsilver compounds with cyclohexenone (Scheme 1.6).29 It was found that the alkylsilver derivatives reacted preferentially, and in some cases exclusively, in the (3 position. A significant amount of 3-methylcyclohex-2-enol was observed for the reaction of Me2AgMgBr, which has been attributed to the elimination and subsequent reaction of silver(I) hydride. Silver(I) hydride has been observed in the gas-phase fragmentation of other organosilver compounds.30... 

As is general for organosilver compounds, perfluorophenylsilver is considerably more stable than phenylsilver.55 The first example of a perfluoroarylsilver compound was reported by Miller and Sun in 1970.49 Reaction of perfluorophenyllithium with silver trifluoroacetate, or of perfluorophenyl bromide with perfluoroisopropylsilver, gave perfluorophenylsilver as colorless crystals (Scheme 1.17). The compound was found to be stable up to 150°C, at which temperature it slowly dimerized to give perfluorobiphenyl and metallic silver. Since this initial report a number of syntheses of perfluorophenylsilver from perfluorophenyllithium followed.56,57... 

The use of silver acetylides to effect useful synthetic transformations has been perhaps more widely reported than the use of any other organosilver compound, as previously reviewed by Pale et al.81 and Sladkov et al.82 Their use, however, in comparison to that of other metal acetylides (Na, Cu, Li), has perhaps been limited by their relatively low reactivity and/or solubility. The silver acetylides are, however, generally comparatively more stable than the more commonly used metal acetylides, as they can be... 

Silver acetylides undergo oxidative condensation in the presence of cupric chloride to give diynes.124 Dimerization is a reaction common to a number of organosilver compounds, including both alkyl- and arylsilver derivatives. 

In conclusion, it is clear that much scope remains for the development of methodology that exploits the unique chemistry of organosilver compounds. From the methods... 

Schmidbaur, H. Bayler, A. Synthesis and uses of organosilver compounds, in The Chemistry of Organic Derivatives of Gold and Silver, Patai, S. Rappoport, Z., eds., Wiley, Chichester, UK, 1999, pp. 211-226. 

As for the cyclopropane rearrangement, the reaction probably involved the formation of a cationic silver cationic species followed by regioselective o-bond migration, leading preferentially to the more stable carbocation intermediate that is finally intramolecularly trapped by the organosilver species (Scheme 3.25).39... 

Taking into account this lack of stereoselectivity and equilibration between allenic stereoisomers, Benn proposed a mechanism in which silver ion facilitates the acyloxy shift on formation of n complex (or a bridged ionic silver intermediate).52 The thus-formed acetoxyallenes would remain coordinated to silver, allowing the formation of an organosilver allyl cation. Free rotation at this stage would provide both acetoxy-allene isomers after reversible loss of silver (Scheme 3.32). 

Organosilver Species as Intermediates in Catalyzed Enyne or Arylyne Synthesis... 

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