4 FLP-Mediated C–H-Activation
121
CatB Cl
+ Et 3 Si[CbBr 6 ]
[CbBr 6 ] = [closo-1-H-CB 11 H 5 Br 6 ]
[CatB][CbBr 6 ]
- Et 3 SiCl
H
CatB
CatB
L
H
PhBCat
H
PhBCat
HL
+
+
EAS Mechanism
C-H Insertion Mechanism
L = a weak nucleophile
e.g. CatBH, Et 3 SiCl
Int4
Int5
Int6
Scheme 4.5 Possible mechanistic pathways for the borylation of benzene using in situ generated
borenium cation Int4
N
R 1
NMe 2
Me 2 N
[BBN]
R 2
N
R 1
R 2
BBN
+
Tf 2 N
4 examples
- Tf 2 NH
50 °C
CH 2 Cl 2
Vedejs (2011)
Ar-H
CatB NEt 3 [AlCl4]
1) 20 °C, CH 2 Cl 2
2) pinacol, Et 3 N
Ar BPin
+
10 examples
Ingleson (2011)
Ingleson (2012)
S
B
S
NEt 3
Cl
1) Me 2NTol, Al 2 Cl 6
2) 2-Methylthiophene
S
Me
B
S
S
N
Me
Me
H
B
S
S
+
[AlCl4]
+
[Me 2 N(H)tol][AlCl 4 ]
Scheme 4.6 Examples of stoichiometric borylation of various (hetero-)arenes using different boron
cations