Cyclopropanes mercury salts

One major advantage of the alkoxymercuration-demercuration approach to ethers over the acid-catalyzed process is the fact that carbon skeleton rearrangements are seldom observed. Only unsaturated cyclopropanes,42S>426 or aryl-substituted alkenes427 428 in the presence of highly electrophilic mercury salts afford rearranged products. 

Mercury salts have previously been shown to be capable of cleaving cyclopropyl bonds. Phenyl-substituted cyclopropanes react with mercury(II) acetate to give 3-mercurio-l-methoxy-l-phenylpropane derivatives, which can undergo further reactions such as reduction with sodium borohydride or addition to alkenes. For example, treatment of phenyl-cyclopropane (1) with mercury(II) acetate in methanol, followed by the addition of sodium chloride, produced 3-(chloromercurio)-l-methoxy-l-phenylpropane(2) in good yield.When the primary mercury adduct was reacted with alkenes without isolation, the yields were lower than those in the two-step transformation. ... 

Organomercury compounds such as ICFbHgl and Hg(CH2Br)2 may be prepared by the reaction of metallic mercury with diiodomethane or by reaction of mercury(II) salts with diazoalkanes. These mercury derivatives are related to the intermediate that has been proposed in the Simmons-Smith reaction, and likewise, they have been found to convert alkenes into cyclopropanes.92... 

The first stereochemical study of the cleavage of a cyclopropane derivative by a mercuric salt was reported by DeBoer and DePuy 22). By the series of reactions given (Eq. (30)), they showed that 1-phenyl-cts, fyaws-2,3-dimethylcyclopropanol 33) and l-phenyl- ra s, methyl ethers, react with mercuric acetate in acetic acid exclusively with inversion of configuration at the carbon to which the mercury becomes attached. More recently... 

Although cyclopropanes are far less reactive than alkenes, they can be opened by various electrophiles including protic acids, bromine, chlorine, mercury(II) salts and acetyl chloride. The ring-cleavage processes of cyclopropanes by electrophiles were studied with the aid of ab initio molecular orbital and other calculations. Early studies assumed that traditional... 

Cyclopropanes are activated to protolytic cleavage by electron-withdrawing substituents.They can be cleaved as well with mercury(II) salts " or with tin(lV) chlo-ride instead of protons. 

The more substituted systems rearranged simply on warming in 2,2,2-trifluoroethanol but the assistance of silver(I) or mercury(II) salts was necessary to achieve cyclization of the less highly substituted compounds. In the formation of 3-(phenylmethylene)tetrahydropyran, cyclization occurred at the less highly substituted cyclopropane carbon atom, in the disrotatory mode, to give the product as a single isomer. ... 

The Hunsdiecker process has the disadvantage of requiring dry silver salts. As a consequence, other methods have been sought, and it has been found that some carboxyhc acids undergo oxidative decarboxylation on formation of mercury (Hg), lead (Pb), or copper (Cu) salts. For example, cyclopropane carboxyhc acid, on treatment with bromine (Br2) in the presence of red mercury(II) oxide (HgO), yields hydrogen bromide (HBr), carbon dioxide (CO2), and bromcxyclopropane (cyclopropyl bromide) as shown in Equation 9.84. 

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