Alkylmercury halides

The photostimulated reaction of alkylmercury halides with ArS02Y yields RY, where Y = Cl or SePh, according to the mechanism given in equations 49-5035. In the case of the... 

The nature of the electrode plays a significant role in the direction and often the products of electrochemical processes, particularly reduction. Metals that can form relatively stable organometallics with the substrate under study often intervene directly to produce a product like that of direct organometallic reaction. The electro reduction of alkylmercury halides was studied on Pt, Hg and carbon electrodes. Whereas at Pt and carbon electrodes two-electron reduction was observed, at mercury-coated electrodes multistep reduction occurred and RHgHgX was observed213. 

The electrophilic PhCOCH2 radical generated by photolysis of PhCOCH2HgCl in DMSO adds readily to enamine 10b to form the substituted enamine 18, which upon hydrolysis gives the 1,4-diketone 19 in 60% overall yield29. In this free radical chain reaction (Scheme 2), the electron transfer from the easily oxidizable adduct radical 17 to PhCOCH2HgCl is facilitated by the fact that the irreversible half-wave reduction potentials of alkylmercury halides are typically more positive than — 0.6 V30. 

Carbon—Carbon Cleavage. As mentioned above, carbon—carbon cleavage usually accompanied the normal carbon-mercury cleavage reaction. While this chain-shortening process was most prominent for the n-alkylmercuric halides which were ozonated at 10°C (Reactions I and 6, Table I), it was reduced to a much lower level when the di-n-alkylmercurials were ozonated at —76°C (Reactions 5 and 10, Table I). Actually even less carbon—carbon scission occurred during the ozonation of the di-s-alkylmercurials halides (Reaction 14, Table I) and during the partial ozonation of the lerl-alkylmercuric halides (not listed). 

Photostimulated addition of r-butylmercury halides to 1,6-dienes (539) and enynes yields cyclised primary alkylmercury halides (540) from 5-exo cyclisation of the intermediate adduct radicals. In some related cases, unfavourable rotamer populations militate against efficient cyclisation. ... 

The free radical chain reaction between PhCOCHjHgCl and 1-morpholinocyclohex-cne has been reported to involve addition of the acceptor radical PhCOCHj- to the jS-position of the enamine followed by electron transfer to regenerate the attacking radical (Scheme 19). Photostimulated reactions of simple alkylmercury halides failed since an electrophilic radical is required. Photolysis of p-nitrobenzyl chloride in the presence of enamines gave the -/>-nitrobenzyl ketone on hydrolysis . Radical mediated reductive alkylation of acyclic-enamines has also been reported with radical precursors such as PhSCH2CN, PhS02CH2Cl and Me3CS02CH2SePh . Reductive alkylation also occurred with chloromethyl p-tolyl sulphone in the presence of tributyltin hydride and azobis(isobutyronitrile) (AIBN) (Scheme 20). 

Reduction of an alkylmercury halide or acetate with a borohydride provides an alternative method for accessing a carbon radical species (see Scheme 4.11). The alkylmercury compound can be prepared by one of a number of methods, such as from the corresponding Grignard reagent or from addition of Hg(OAc)2 to an alkene. For example, intramolecular amido-mercurafion of the alkene 50, followed by formation of the alkyl radical and addition to methyl acrylate provides a route to the alkaloid 8-coniceine (4.46). ... 

R can be alkyl or aryl and R has usually been aryl 212, 214), though more recently the dimethyl compounds (CH3)2AsMgX (X = Br, I) have been prepared 194, 204). Trialkyl- and triarylarsines react with alkylmercury halides affording salts containing ions such as [CH3HgAs(C2Hs)3] 288a). 

The electrolysis of solutions of the lower alkylmercury halides in liquid ammonia results in the deposition on the cathode of an electrically conducting solid of metallic appearance, which decomposes at room temperature into equimolar proportions of R Hg and Hg. The methyl derivative is the easiest to obtain. It was the first example of an organic metal to be described and appears to consist of MeHg cations and an equivalent number of free electrons. Its possible formulation as consisting of free radicals, or RHgHgR or amalgams of Hg -h RHg, has been excluded in various ways. 

Reactions of electron acceptor radicals with alkylmercury halides 306... 

The reactions of alkylmercury halides with nucleophiles under free radical conditions (i.e. photostimulation, heat, ultrasound) follows the Srn reaction path. However, apparently RHgX is not a reaction intermediate, and electron transfer from the radical anion to RHgX is dissociative. Thus, reactions (4) and (5) of Scheme 10 occur in a concerted fashion to yield the two step chain process of Scheme 13. Evidence for the dissociative electron... 

Alkylmercury halides or carboxylates undergo a free radical aromatic substitution reaction with pyridine, pyridinium ions or dialkylanilines. Addition of R to these substrates produces the easily oxidized radicals... 

REACTIONS OF ELECTRON ACCEPTOR RADICALS WITH ALKYLMERCURY HALIDES... 

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