Electronic control of chiral quaternary center creation in the intramolecular asymmetric heck reaction.
The Boehringer-Ingelheim phosphinoimidazoline (BIPI) ligands were applied to the formation of chiral quaternary centers in the asymmetric Heck reaction. Several different substrates were examined in detail, using more than 70 members of this new ligand class. Hammett relationships were determined through systematic variation of the ligand electronics. All substrates showed essentially the same Hammett behavior, where enantioselectivity increased as the ligands were made more electron-deficient. Ligand optimization has led to catalysts which give the highest enantioselectivities reported to date for these difficult systems.
Busacca
Carl A
CA
Departments of Chemical Development and Analytical Sciences, Boehringer-Ingelheim Pharmaceuticals, Inc., 900 Ridgebury Rd., Ridgefield, Connecticut 06877, USA. cbusacca@rdg.boehringer-ingelheim.com
Grossbach
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D
Campbell
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SJ
Dong
Yong
Y
Eriksson
Magnus C
MC
Harris
Robert E
RE
Jones
Paul-James
PJ
Kim
Ji-Young
JY
Lorenz
Jon C
JC
McKellop
Keith B
KB
O'Brien
Erin M
EM
Qiu
Fenghe
F
Simpson
Robert D
RD
Smith
Lana
L
So
Regina C
RC
Spinelli
Earl M
EM
Vitous
Jana
J
Zavattaro
Chiara
C