|
Carbometalation 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+. ==Scope== In one study methylphenylacetylene is reacted with phenylmagnesium bromide to a vinyl magnesium bromide which is quenched with water:〔''Arylmagnesiation of Alkynes Catalyzed Cooperatively by Iron and Copper Complexes'' Eiji Shirakawa, Takafumi Yamagami, Takahiro Kimura, Shigeru Yamaguchi, and Tamio Hayashi J. Am. Chem. Soc.; 2005; 127(49) pp 17164 - 17165; (Communication) 〕〔In this reaction the Grignard reagent together with iron acetylacetonate and tributylphosphine first form an ill-defined aryliron intermediate and then by reaction with copper(I) chloride an intermediate cuprate〕 Another demonstration of this reaction type is an alternative route to tamoxifen starting from diphenylacetylene and ethyllithium:〔''Carbolithiation of Diphenylacetylene as a Stereoselective Route to (Z)-Tamoxifen and Related Tetrasubstituted Olefins'' Neola F. McKinley and Donal F. O'Shea J. Org. Chem.; 2006; 71(25) pp 9552 - 9555; (Note) 〕 The capturing electrophile here is triisopropyl borate forming the boronic acid R-B(OH)2. The second step completing tamoxifen is a Suzuki reaction. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Carbometalation」の詳細全文を読む スポンサード リンク
|