Advances in C–C and C–X Coupling Using Palladium–NHeterocyclic Carbene (Pd–NHC) Complexes - New Trends in Cross-Coupling: Theory and Applications - page 161

was capable of promoting the coupling between primary bromides and
alkyl organozinc reagents to create sp 3 -sp 3 bonds in high yields, at room
temperature, in THF-NMP (2:1) as solvent (Scheme 4.13).
One year later, Organ et al. developed the first well-defined palladium
precatalyst to achieve the cross-coupling, namely [Pd(IPr)(PEPPSI)] (15,
Scheme 4.14). 75 The system proved highly ecient in Negishi coupling,

Pd 2 (dba) 3 (2mol%)
IPr.HCl (8 mol%)

R R' R

+

Br ZnBr R'

THF / NMP (2:1)
RT, 24 h

O

O

EtOOC

N

NC

O

O

92% 65% 75%

O

CN

SiMe 3

COOEt

O

61% 62%

Scheme 4.13 Negishi coupling using an in situ-generated catalyst system for the
formation of sp 3 -sp 3 bonds.

[Pd(IPr)(PEPPSI)] ( 15 )
(1 mol%)

RX + ' ZnB r R R'

NN

THF / NMP or THF / DMI
RT - 60°C, 2 h

sp 3 -sp 3 :

Me 3 Si

Cl Pd Cl

CN

N

X=Cl,RT:74%

Cl
[Pd(IPr)(PEPPSI)]
15

O

N

CN

O

X=OTs,RT:70%

sp 2 -sp 2

MeO

X=Br,RT:80%

sp 3 -sp 2 : sp 2 -sp 3 :

OMe

OMe

X=Cl,60°C:89%

COOEt

NC

N

N

X=Br,RT:87% X=Cl,RT:98%

MeO

O t Bu

X=Cl,RT:90%

O

N

S

Ph

Me 3 Si CO OEt

NN

X=Cl,RT:89% X=Br,RT:83% X=Cl,RT:96%

Scheme 4.14 Negishi coupling using the well-defined [Pd(IPr)(PEPPSI)] precatalyst.