L. Yu et al. / Journal of Organometallic Chemistry 705 (2012) 75e78
77
Table 3
Table 4
Synthesis of phenazines by complex 1 catalyzed homocoupling of 2-bromoanilines
Synthesis of phenazines by complex
different 2-iodoanilines.
1
catalyzed cross-coupling between two
in water.a
N
N
N
N
NH2
Br
Complex 1
R
R
R
K2CO3, PTC
H2O
NH2
I
I
N
N
Complex 1
4
+
N
H2N
K2CO3, PTC
H2O
N
5
Yield [%]b
72
1
2
3
Entry
1
2-Bromoaniline
Product
NH2
N
3 Yield [%]a
4 Yield [%]a
5 Yield [%]b
Br
N
Entry
1
2
1
2
3
1.0
1.0
1.0
1.0
3.0
5.0
38
48
61
42
26
15
44
70
62
NH2
N
2
3
77
80
Br
N
N
a
Isolated yield based on 1.
Isolated yield based on 2.
b
NH2
Br
3. Conclusions
N
In summary, we have developed a simple, efficient, economical
and environmentally friendly protocol for the synthesis of phena-
zines via Cu-catalyzed homocoupling of 2-halogen anilines in water.
This methodology could be also successfully applied to coupling
reactions between two different 2-iodoanilines in moderate yields.
NH2
N
N
O
4
56
O
O
Br
NH2
Br
N
N
NO2
5
6
44
44
4. Experimental section
O2N
Cl
O2N
Cl
Typical Procedure for the Catalysis: Catalyst (0.05 mmol), 2-
halogen aniline (0.5 mmol), K2CO3 (1.0 mmol), (nBu)4NBr
(0.1 mmol), and water (10 mL) were added to a sealed tube. The
reaction mixture was stirred at 120 ꢀC for 30 h and then cooled to
room temperature and extracted with ethyl acetate. The organic
layer was then dried with anhydrous Na2SO4, and the solvent was
removed under reduced pressure. The product was finally obtained
by column chromatography on silica gel. All the products were
confirmed by 1H and 13C NMR spectroscopic analysis.
NH2
N
N
Cl
Br
N
N
F
NH2
Br
7
58
F
F
a
Reaction conditions: 2-bromoaniline (0.5 mmol), complex
(nBu)4NBr (20 mol%), K2CO3 (1 mmol), H2O (10 mL), 120 ꢀC, 30 h.
1
(10 mol%),
b
Isolated yield.
Acknowledgments
This project was sponsored by the Natural Science Foundation of
China (Nos. 20901052, 21072132), Sichuan Provincial Foundation
(08ZQ026-041) and Ministry of Education (NCET-10-0581).
Appendix. Supplementary data
Supplementary data associated with this article can be found, in
Fig. 2. The X-ray crystal structure of 2,7-dimethylphenazine.
References
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was further unambiguously confirmed by single-crystal X-ray
analysis (Fig. 2).
Encouraged by the results obtained, we proceeded to apply this
catalytic system to the cross-coupling reactions between different
2-iodoanilines. As shown in Table 4, 2-iodoaniline (1 equiv.) and 2-
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under the optimized reaction conditions to afford the desired 38%
cross-coupled product, while the symmetric products were found to
be the main side products (Table 4, entry 1). When the molar ratio of
the two substrates was changed to be 1:3 or 1:5, 48% or 61% yields of
1,3-dimethylphenazine could be obtained (Table 4, entries 2-3).
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