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.
Departments of Chemical Development and Analytical Sciences, Boehringer-Ingelheim Pharmaceuticals, Inc., 900 Ridgebury Rd., Ridgefield, Connecticut 06877, USA. cbusacca@rdg.boehringer-ingelheim.com
Carl A
CA
Busacca
Danja
D
Grossbach
Scot J
SJ
Campbell
Yong
Y
Dong
Magnus C
MC
Eriksson
Robert E
RE
Harris
Paul-James
PJ
Jones
Ji-Young
JY
Kim
Jon C
JC
Lorenz
Keith B
KB
McKellop
Erin M
EM
O'Brien
Fenghe
F
Qiu
Robert D
RD
Simpson
Lana
L
Smith
Regina C
RC
So
Earl M
EM
Spinelli
Jana
J
Vitous
Chiara
C
Zavattaro