4 FLP-Mediated C–H-Activation
143
N
B
H 2
NMe
H
TS13
Metal-free C-H bond activation
N
Me
16 (2.5 mol%)
HBR 2 (1 equiv.)
80 °C
CDCl 3
N
Me
BR 2
H-H
+
HBR 2
HBPin
HBCat
9-BBN
Yield [%] 2
93
42
60
N
B
H
H
B
N
16
H
H
Scheme 4.35 Catalytic borylation reaction of 1-Me-pyrrole using aminoboranes
only yielded the 3-substituted isomer. The reaction was shown to be tolerant towards
aryl or alkyl halides, epoxides, ethers, hexamethylphosphoramide and less basic
amines, but inhibition was observed in the presence of more basic amines, carbonyl
groups, or unsaturated hydrocarbons (Scheme 4.36).
Scheme 4.36 Scope over
various N-protected pyrroles
towards the catalytic
borylation reaction with 16
N
R
16
HBPin
80 °C, 16 h
CHCl 3
N
R
N
R
BPin
BPin
+
Me
Bn
TIPS
93 %
60 %
98 %
7 %
40 %
0 %
E
16 (2.5 mol%)
HBPin
80 °C, 16 h
CHCl 3
E
BPin
N
BPin
Me
85%
85%
81%
62%
S
MeO
BPin
O
MeO
BPin
O
BPin
Scheme 4.37 Isolated yields for selected examples of the catalytic borylation reaction promoted
by 16