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OMe
H
N
N
N
N
H
H
O
Pd(OAc)
2
(10 mol%)
Ag
2
CO
3
(1 equiv)
4-OMeC
6
H
4
I(1.5equiv),
t
BuOH, 80 °C, 24h
H
95%
H
O
H
H
H
H
O
HN
O
HN
H
78%
N
N
OMe
Scheme 12.43 Arylation of g-C
sp
3
-H aliphatic amines.
OH
OTBS
OTBS
OH
CH
2
O
2
Me
CH
2
O
2
Me
Pd(OAc)
2
(15 mol%)
Ag
2
CO
3
(1 equiv)
4-NO
2
C
6
H
4
I(1.5equiv)
t
BuOH, 70 °C, 40h
O
NH
HN
O
H
HN
O
O
O
N
OTBS
N
OTBS
NO
2
NO
2
(+)-obafluorin
Scheme 12.44
Synthesis of (+)-obafluorin from a threonine derivative.
O
I
Pd(OAc)
2
(10 mol%)
Ag
2
CO
3
(1 equiv)
H
O
H
H
N
t
BuOH, 80 °C, 2h
N
CO
2
H
(1 equiv)
88%
Scheme 12.45 Direct arylation of
the C
sp
3
-H bond in an intramolecular
transformation.
picolinamide (Scheme 12.43). The synthetic utility of this method was
demonstrated by synthesizing (+)-obafluorin from a threonine derivative
(Scheme 12.44).
Chen and co-workers also utilized 8-aminoquinoline as a directing group
for the Pd-catalyzed direct arylation of the C
sp
3
-H bond in an intramolecular
transformation depicted in Scheme 12.45.
74
In this context, in addition to 8-aminoquinoline, carboxylic acid moieties
were used as the directing group for the activation of aliphatic C
sp
3
-H
bond.
27
Aliphatic carboxylic acids were arylated by using Ar-B(OR)
2
(Scheme 12.46) and a Pd
0
/Pd
II
cycle was proposed. However, with an aryl
iodide as coupling partner, a Pd
II
/Pd
IV
cycle was suggested (Scheme 12.47).
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