76
3.3.7.2 C–H and O–M as Nucleophiles
Organometallic reagents containing O–M bonds have seldom been utilized as
nucleophiles in oxidative cross-coupling. One example is demonstrated by Zhang
and co-workers that in the presence of Pd(TFA) 2 , the oxidative coupling of indoles
with AgOAc under oxygen atmosphere afforded the C3-position acetoxylated biindolyls in good yields (Scheme 3.50) [108]. Only electron-rich indoles were suitable substrates in this transformation.
92%
89%
95%
CaX 2 , HOAc, 110 °C
H
Ar
X
Ar
Cl
Cl
Br
Br
74%
N
N
N
N
Pd(OAc) 2 (5 mol%)
Cu(OTFA) 2
N
N
N
N
N
N
N
N
OMe
MeO
OMe
Scheme 3.48 Pd-catalyzed chlorination and bromination of 2-arylpyrimidines using calcium
halides as the halogen sources
H
R
O
N
H
N
CuI, NMO
or
H
R
N
H
O
N
Me Me
AgF
DMF or DMPU
F
R
O
N
H
N
or
F
R
N
H
O
N
Me Me
F
F
Scheme 3.49 Cu-mediated bidentate auxiliary-directed oxidative Csp
2 –H fluorination
C. He
3.3.7.2 C–H and O–M as Nucleophiles
Organometallic reagents containing O–M bonds have seldom been utilized as
nucleophiles in oxidative cross-coupling. One example is demonstrated by Zhang
and co-workers that in the presence of Pd(TFA) 2 , the oxidative coupling of indoles
with AgOAc under oxygen atmosphere afforded the C3-position acetoxylated biindolyls in good yields (Scheme 3.50) [108]. Only electron-rich indoles were suitable substrates in this transformation.
92%
89%
95%
CaX 2 , HOAc, 110 °C
H
Ar
X
Ar
Cl
Cl
Br
Br
74%
N
N
N
N
Pd(OAc) 2 (5 mol%)
Cu(OTFA) 2
N
N
N
N
N
N
N
N
OMe
MeO
OMe
Scheme 3.48 Pd-catalyzed chlorination and bromination of 2-arylpyrimidines using calcium
halides as the halogen sources
H
R
O
N
H
N
CuI, NMO
or
H
R
N
H
O
N
Me Me
AgF
DMF or DMPU
F
R
O
N
H
N
or
F
R
N
H
O
N
Me Me
F
F
Scheme 3.49 Cu-mediated bidentate auxiliary-directed oxidative Csp
2 –H fluorination
C. He