Efficient Boron−Copper Additions to Aryl-Substituted Alkenes Promoted by NHC−Based Catalysts. Enantioselective Cu-Catalyzed Hydroboration Reactions
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- 17 February 2009
- journal article
- research article
- Published by American Chemical Society (ACS) in Journal of the American Chemical Society
- Vol. 131 (9) , 3160-3161
- https://doi.org/10.1021/ja809382c
Abstract
A Cu-catalyzed method for efficient boron−copper addition processes involving acyclic and cyclic disubstituted aryl olefins are reported. Reactions are promoted with 0.5−5 mol % of a readily available N-heterocyclic carbene (NHC) complex; the presence of MeOH promotes in situ protonation of the C−Cu bond and leads to efficient catalyst turnover, constituting a net Cu-catalyzed hydroboration process. Reactions proceed in >98:<2 site selectivity and furnish secondary organoborane isomers that complement those obtained through reactions of boron-hydride reagents or by Rh- or Ir-catalyzed hydroborations (benzylic secondary C−B bonds). Initial observations regarding processes catalyzed by chiral NHC complexes, delivering products in up to 99:1 enantiomeric ratio, are disclosed.Keywords
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