Iodomethane reaction with zinc

Di-iodomethane reacts with zinc to produce a carbenoid reagent which adds to olefins in the Simmons-Smith cyclopropanation (Fig. 41).23i The reaction is carried out after a preliminary activation of the metal, which can be of low-grade purity ("mossy zinc"). Even if conducted under solvent reflux, i.e., conditions of low-intensity cavitation, the sonochemical procedure offers the advantage of... 

Gomberg was the first to characterize a free radical when, in 1900, he generated triphenylmethyl radical 5 by reacting chlorotriphenylmethane (4) with zinc metal.l Triphenylmethyl radical 5 is unusual in that it is quite stable and its formation is probably the first experimental verification of a free radical. Frankland, however, may have been the first to generate transient methyl and ethyl radicals in the reaction of iodomethane and iodoethane with zinc, in 1849.2 In the last 30 years, attention has been focused on radicals, their reactivity, and their applications to organic synthesis. Excellent monographs by Davies and Parrott, Lazar et al., Hay, ... 

The use of iodoform as the reagent precursor under Furukawa s conditions gives rise to a more complex scenario, since the additional C—I bonds can further react with an ethylzinc species (equation 8)" . The reaction of the iodo-substituted zinc carbenoid with an alkene will generate an iodo-substituted cyclopropane, whereas that involving the gem-dizinc carbenoid will lead to a cyclopropylzinc product. The evidence for the formation of a. gem-dizinc carbenoid was obtained not only by the analysis of the cyclopropanation products but also by the formation of rfi-iodomethane upon quenching the reagent with D2O/DCI. 

As shown in equation 55, when the benzyl ether of ci.s-2-butcn-1,4-diol is treated with bis(iodozincio)iodomethane, the cyclopropylzinc intermediate is obtained and reacts with various electrophiles. The obtained cyclopropyl derivative has all-d.v configuration. In this reaction, zinc halide, which is present in the solution, plays an important role79. 

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