Chemistry Reference
In-Depth Information
O
MeO
OMe
Ph
O
Ph
H
Ph
Ph
d
n
4
r
4
n
g
|
1
OH
H
Ru
H
O
OC
OC
H
MeO
OMe
Ph
NH
2
OH
OH
OH
H
H
NH
2
N
Ph
NH
Ph
Ph
Ph
-NH
3
O
Ph
O
Ph
Ph
Ph
Ph
Ph
Ru
R
u
OC
OC
OC
OC
O
H
Ph
H
OH
MeO
OMe
Ph
Ph
O
H
Ph
Ph
O
.
OH
R
u
O
OC
OC
H
N
MeO
OMe
O
Scheme 1.9 Proposed mechanism for the oxidative coupling that gives benzoxazole.
synthesis of pharmaceutically important heterocyclics under environ-
mentally benign reaction conditions.
1.2.3.2 Copper-Mediated Heterocycle Synthesis
Another recent report on the preparation of benzimidazoles, benzoxazoles
and benzothiazoles directly from aromatic alcohols and o-phenylenedia-
mine, o-aminophenol and o-aminothiophenol exploits a simple but
ecient Cu(I)/TEMPO/Bpy catalytic system under ambient conditions
(Scheme 1.10).
50
N-Heterocycles can also be prepared using alcohol oxidation as a key
synthesis step. The potential of the Cu/TEMPO/O
2
catalytic system as an
aerobic oxidation catalyst was explored by Cook and co-workers for the
synthesis of substituted indoles and quinolones.
51
Different Cu(
I
) and Cu(
II
)
salts, N-N-ligands (such as 2,2
0
-bipyridine and 1,10-phenanthroline), bases
and TEMPO combinations were screened. The study indicated that the
Search WWH ::
Custom Search