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Hemilabile BINAP(O) as a Chiral Ligand in Desymmetrizing Mizoroki–Heck Cyclizations
Author(s) -
Wöste Thorsten H.,
Oestreich Martin
Publication year - 2012
Publication title -
chemcatchem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.497
H-Index - 106
eISSN - 1867-3899
pISSN - 1867-3880
DOI - 10.1002/cctc.201200300
Subject(s) - binap , chemistry , denticity , ligand (biochemistry) , palladium , heck reaction , stereochemistry , medicinal chemistry , enantioselective synthesis , organic chemistry , catalysis , crystal structure , biochemistry , receptor
BINAP(O), rarely used as a chiral ligand, was found to induce significantly higher levels of enantioselection in representative desymmetrizing Mizoroki–Heck cyclizations where conventional BINAP produces essentially racemic material. BINAP(O) is a ligand with a stronger and weaker donor atom, and that hemilabile nature lends itself the ability to act as either a bi‐ or monodentate ligand. On that basis, we introduce mechanistic models where the weak donor, in one case, mediates the equilibration of diastereomeric alkene–palladium(II) complexes and, in another case, dissociates from the palladium(II) atom, thereby rendering BINAP(O) as a monodentate ligand. These new findings, along with the recently reported effects in intermolecular Mizoroki–Heck reactions, suggest that BINAP(O) ought to be included into ligand screenings.