The hitherto unprecedented palladium-catalyzed cross-coupling of ()-β-bromo-β-arylethenylboranes can be made to proceed satisfactorily through (1) the use of highly catalytically active bis(tri--butylphosphine)palladium or dichloro[,-bis-(2,6-diisopropylphenyl)imidazol-2-yl](-chloropyridine)palladium and (2) conversion of dibromoboryl group to (pinacol)boryl group. Thus, a wide variety of carbon groups can be used to substitute bromine in ≥98% stereo- and regioselectivity, while suppressing the otherwise dominant β-debromoboration. Together with the alkylethyne-based protocols, the alkyne bromoboration-Negishi coupling tandem process has emerged as the most widely applicable and highly selective route to trisubstituted alkenes including those that are otherwise difficult to access.
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| http://dx.doi.org/10.1002/adsc.200900766 | DOI Listing |
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