Handbook of Functionalized Organometallics Applications in S

410
10 Functional Organonickel Reagents
R-Br + R 2
R 1
R 1
R 2
+ Ph-MgBr NiCl 2(dppf) R 2
R=i-C 3H 5,R 1 =Me,R 2 =H 91%(E/Z =67:33)
R=c-C 6H 11, R 1 =H,R 2 =Ph 60%(E/Z =100:0)
Unactivated secondary alkyl bromides and iodides have been shown to proceed
Suzuki couplings with arylboronic acid in the presence of Ni(COD) 2 and bathophenathroline
ligand [94].
R alkyl-X + (HO) 2B-R
X=Br,I
Ni(COD) 2/bathophenanthroline
KOt-Bu
Ph Ph
N N
bathophenanthroline
R
R 1
R alkyl-R
Negishi cross-coupling reactions of primary and secondary alkyl bromides and
iodides are achieved when Ni(COD) is employed as the catalyst in the presence of
a diamine ligands such as bupybox [95].
I
+
O
N
R 1
O
BrZn NEt 2
N
R 1 -Pybox
4
N
O
R 1
Ni(COD) 2/s-Bu-Pybox
78%
H O
N
H
N
O
N
H
Indanyl-Pybox
H
R 1
Ph
4
O
R 2
NEt 2
Recently,nickel-catalyzed cross-couplings of organosilicon reagents with unactivated
secondary alkyl bromides have been disclosed. Functional groups such as
fluoride,chloride,ether,lactones,ketones,acetals,and cyanides are stable under
the reaction conditions. Bathophenanthroline appears to be the best ligand for
these transformations [96].
R alkyl -X
+
F 3Si Ph
NiBr2.diglyme/bathophenanthroline CsF
O
R alkyl -X (Yield %)
O
H
H I
NC I
(60)
(73)
R alkyl -Ph