PSiP-Pincer Type Palladium-Catalyzed Dehydrogenative Borylation of Alkenes and 1,3-Dienes
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19
摘要:
Dehydrogenative borylation of alkenes and 1,3-dienes was realized by carrying out the reaction in the presence of bis(pinacolato)diboron (B2pin2) and a catalytic amount of PSiP-pincer palladium complex. This protocol has the following notable features. 1) Monoanionic nature of the PSiP-pincer ligand prevents the formation of boryl(hydrido)- or dihydridopalladium species, enabling synthesis of various vinyl- or dienylboronic esters in good yield from a 1:1 mixture of B2pin2 and alkenes or 1,3-dienes without forming hydroboration or hydrogenation products. 2) Due to the strong trans influence of the silicon atom, PSiP-pincer palladium complex showed high activity toward migratory insertion. 3) Suppression of these side-reactions and the high reactivity of the PSiP-pincer palladium complex enabled an efficient, successive dehydrogenative borylation to give 1,1- or 1,2-diborylated products depending on the kind of substituent on alkenes by using more than 2 equivalents of B2pin2. Mechanistic study revealed that PSiP-pincer borylpalladium complex was generated from hydridopalladium complex and B2pin2, and this complex underwent alkene insertion followed by β-hydride elimination to give alkenylboronic ester with regeneration of the hydridopalladium complex.
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DOI:
10.1246/bcsj.20130004
被引量:
年份:
2013
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