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In Quest of Factors That Control the Enantioselective Catalytic Markovnikov Hydroboration/Oxidation of Vinylarenes
Author(s) -
Segarra Anna M.,
DauraOller Elias,
Claver Carmen,
Poblet Josep M.,
Bo Carles,
Fernández Elena
Publication year - 2004
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200400574
Subject(s) - hydroboration , chemistry , enantioselective synthesis , catalysis , rhodium , cationic polymerization , medicinal chemistry , reagent , catalytic cycle , enantiomer , markovnikov's rule , organic chemistry , regioselectivity
This study attempts to rationalise the unpredictable performance of transition metal catalysed asymmetric hydroboration of vinylarenes on varying the precursor of the catalyst from cationic to neutral species, [M(cod)( L– L)]BF 4 , [M(μ‐Cl)(cod)] 2 /(L–L), the metal (M=Rh and Ir), and the hydroborating reagent (catecholborane, pinacolborane). The approaches are based on the agreement between experimental data provided by ( R )‐Binap and ( R )‐Quinap modified catalytic systems and computational data evidenced by DFT calculations and QM/MM strategies. Unprecedentedly high enantiomeric excesses in the hydroboration/oxidation of vinylarenes with both electron‐withdrawing substituents (( R )‐(+)‐1‐ p ‐F‐phenylethanol, ee up to 92 %) and electron‐releasing substituents (( R )‐(+)‐1‐ p ‐MeO‐phenylethanol, ee up to 98 %), can be attributed to a rhodium halide key intermediate.