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Boron Lewis Acid‐Catalyzed Hydroboration of Alkenes with Pinacolborane: BAr F 3 Does What B(C 6 F 5 ) 3 Cannot Do!
Author(s) -
Yin Qin,
Kemper Sebastian,
Klare Hendrik F. T.,
Oestreich Martin
Publication year - 2016
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.201603466
Subject(s) - hydroboration , chemistry , borane , lewis acids and bases , adduct , medicinal chemistry , substituent , boranes , trifluoromethyl , frustrated lewis pair , hydroamination , triflic acid , metathesis , catalysis , alkene , boron , stereochemistry , organic chemistry , alkyl , polymer , polymerization
The transition‐metal‐free hydroboration of various alkenes with pinacolborane (HBpin) initiated by tris[3,5‐bis(trifluoromethyl)phenyl]borane (BAr F 3 ) is reported. The choice of the boron Lewis acid is crucial as the more prominent boron Lewis acid tris(pentafluorophenyl)borane (B(C 6 F 5 ) 3 ) is reluctant to react. Unlike B(C 6 F 5 ) 3 , BAr F 3 is found to engage in substituent redistribution with HBpin, resulting in the formation of Ar F Bpin and the electron‐deficient diboranes [H 2 BAr F ] 2 and [(Ar F )(H)B( μ ‐H) 2 BAr F 2 ]. These in situ‐generated hydroboranes undergo regioselective hydroboration of styrene derivatives as well as aliphatic alkenes with cis diastereoselectivity. Another ligand metathesis of these adducts with HBpin subsequently affords the corresponding HBpin‐derived anti ‐Markovnikov adducts. The reactive hydroboranes are regenerated in this step, thereby closing the catalytic cycle.