Carbometalation
Carbometalation (less often carbometallation) is an organometallic reaction involving the nucleophilic addition to alkenes and alkynes of a diverse range of organometallic reagents such as organolithium compounds, organocopper compounds and Grignard reagents according to the following general alkyne scheme:
The addition can yield the cis or trans isomer and with unsymmetrical alkynes the organometallic compound can add in two different way thus control of regioselectivity is important.
In a follow-up step the sensitive metalalkenyl group is replaced by an electrophile E+.
In one study methylphenylacetylene is reacted with phenylmagnesium bromide to a vinyl magnesium bromide which is quenched with water:
Another demonstration of this reaction type is an alternative route to tamoxifen starting from diphenylacetylene and ethyllithium:
The capturing electrophile here is triisopropyl borate forming the boronic acid R–B(OH)2. The second step completing tamoxifen is a Suzuki reaction.
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