BINAP=2,2′-bis(diphenylphosphino)-1,1′-binaphthyl
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Full Paper
Hemilabile BINAP(O) as a Chiral Ligand in Desymmetrizing Mizoroki–Heck Cyclizations†
Article first published online: 22 AUG 2012
DOI: 10.1002/cctc.201200300
Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Additional Information
How to Cite
Wöste, T. H. and Oestreich, M. (2012), Hemilabile BINAP(O) as a Chiral Ligand in Desymmetrizing Mizoroki–Heck Cyclizations . ChemCatChem, 4: 2096–2101. doi: 10.1002/cctc.201200300
- †
Publication History
- Issue published online: 28 NOV 2012
- Article first published online: 22 AUG 2012
- Manuscript Received: 8 MAY 2012
Funded by
- Deutsche Forschungsgemeinschaft. Grant Number: Oe 249/5-1
Keywords:
- asymmetric catalysis;
- enantioselectivity;
- Heck reaction;
- palladium;
- phosphane ligands
Abstract
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.