Carbomercuration alkynes

Metal-mediated additions of silyl enolates to alkynes also are valuable for intra-and intermolecular vinylation of ketones. The Hg(II)-induced cychzation of alky-nyl-branched SEE provides regio- and stereochemicaUy homogeneous exocychc vinyl mercurial products that can be converted into a variety of functionahzed alkenes [265-267]. Two plausible mechanisms for the intramolecular carbomercura-tion have been proposed, as in the above Pd(II)-mediated cycloaUcenylation-nu-cleophihc enolate addition to the Hg(II)-activated alkyne and concerted addition of an a-keto mercurial species generated by Si-Hg transmetalation. Forsyth et al. have determined that carbomercuration occurs in an anti fashion by the former... 

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