Copper-catalyzed direct amination of ortho-functionalized haloarenes with sodium azide as the amino source

Article abstract of DOI:10.1021/jo100345t

A simple copper-catalyzed direct amination of ortho-functionalized haloarenes (2-halobenzoic acid, 2-halobenzamide, and N-(2-bromophenyl)acetamide derivatives) has been developed with use of NaN₃ as the amino source in ethanol, and the corresponding ortho-functionalized aromatic amines were synthesized in good to excellent yields. The protocol undergoes one-pot Ullmann-type coupling of ortho-functionalized haloarenes with NaN₃ to lead to ortho-functionalized azidoarenes, followed by reduction with ethanol.

Full text of DOI:10.1021/jo100345t

pubs.acs.org/joc
Copper-Catalyzed Direct Amination of Ortho-Functionalized Haloarenes
with Sodium Azide as the Amino Source
Haibo Zhao,†,‡ Hua Fu,*,† and Renzhong Qiao*,‡
†Key Laboratory of Bioorganic Phosphorus Chemistry and Chemical Biology (Ministry of Education),
Department of Chemistry, Tsinghua University, Beijing 100084, People’s Republic of China, and
‡State Key Laboratory of Chemical Resource Engineering, Department of Pharmaceutical Engineering,
College of Life Science and Technology, Beijing University of Chemical Technology, Beijing 100029,
People’s Republic of China
fuhua@mail.tsinghua.edu.cn; qiaorz@mail.buct.edu.cn
Received February 24, 2010
A simple copper-catalyzed direct amination of ortho-functionalized haloarenes (2-halobenzoic acid,
2-halobenzamide, and N-(2-bromophenyl)acetamide derivatives) has been developed with use of NaN3
as the amino source in ethanol, and the corresponding ortho-functionalized aromatic amines were synthe-
sized in good to excellent yields. The protocol undergoes one-pot Ullmann-type coupling of ortho-functiona-
lized haloarenes with NaN3 toleadtoortho-functionalizedazidoarenes,followedbyreductionwithethanol.
Introduction
of the requisite 2-aminobenzoic acid derivatives (Figure 1,
structure A)2,5,6 or 2-aminobenzamide derivatives (Figure 1,
structure B).7 Dihydroquinazolinones display a broad range of
biological, medicinal, and pharmacological properties and are
constituents of antitumor, antibiotic, antidefibrillatory, anti-
pyretic, analgesic, antihypertonic, diuretic, antihistamine, anti-
depressant, and vasodilating agents,8 and 2-aminobenzamide
derivatives (Figure 1, structure B) are important building
blocks for their synthesis.9 Benzimidazoles have attracted much
attention for their wide applications as enzyme inhibitors,10
Nitrogen-containing heterocyclic compounds in the form of
biologically active drugs or agents play an important role in the
pharmaceutical and agrochemical industries.1 Quinazolinone
derivatives are now known to show various useful biological
and medicinal activity, such as hypnotic, sedative, analgesic,
anticonvulsant, antitussive, antibacterial, antidiabetic, anti-in-
flammatory, and antitumor.2,3 Moreover, some therapeutic
agents containing the core structure have been on the market
or are in clinical trials for the treatment of cancer.4 Although
some methods for syntheses of quinazolinone derivatives have
been developed, their preparation depends on the availability
(6) For selected examples, see: (a) Liu, J.-F.; Ye, P.; Zhang, B.; Bi, G.;
Sargent, K.; Yu, L.; Yohannes, D.; Baldino, C. M. J. Org. Chem. 2005, 70,
6339. (b) Roy, A. D.; Subramanian, A.; Roy, R. J. Org. Chem. 2006, 71, 382.
(c) Yoo, C. L.; Fettinger, J. C.; Kurth, M. J. J. Org. Chem. 2005, 70, 6941.
(7) (a) Gellibert, F.; Fouchet, M.-H.; Nguyen, V.-L.; Wang, R.; Krysa,
G.; de Gouville, A.-C.; Huet, S.; Dodic, N. Bioorg. Med. Chem. Lett. 2009,
19, 2277. (b) Roy, A. D.; Subramanian, A.; Roy, R. J. Org. Chem. 2006, 71,
382.
*To whom correspondence should be addressed. Fax: 86-10-62781695.
(1) (a) Landquist, J. K. In Comprehensive Heterocyclic Chemistry; Katritzky,
A. R., Rees, C. W., Eds.; Pergamon: New York, 1984. (b) Crowley, P. J. In
Comprehensive Heterocyclic Chemistry; Katritzky, A. R., Rees, C. W., Eds.;
Pergamon: New York, 1984.
(2) (a) Witt, A.; Bergman, J. Curr. Org. Chem. 2003, 7, 659 and references
cited therein. (b) Mhaske, S. B.; Argade, N. P. Tetrahedron 2006, 62, 9787 and
references cited therein.
(3) (a) Connolly, D. J.; Cusack, D.; O’Sullivan, T. P.; Guiry, P. J.
Tetrahedron 2005, 61, 10153. (b) Ma, Z.; Hano, Y.; Nomura, T. Heterocycles
2005, 65, 2203.
(8) (a) Yale, H. L.; Kalkstein, M. J. Med. Chem. 1967, 10, 334. (b) Neil,
G. L.; Li, L. H.; Buskirk, H. H.; Moxlcy, T. E. Cancer Chemother. 1972, 56,
163. (c) Bonola, G.; Da Re, P.; Magistretti, M. J.; Massarani, E.; Setnikar, I.
J. Med. Chem. 1968, 11, 1136. (d) Alaimo, R. J.; Russel, H. E. J. Med. Chem.
1972, 15, 335. (e) Levin, J. I.; Chan, P. S.; Bailey, T.; Katocs, A. S.;
Venkatesan, A. M. Bioorg. Med. Chem. Lett. 1994, 4, 1141.
(4) For example, Raltitrexed (Tomudex, marketed for colorectal cancer),
Ispinesib (phase II for solid tumors), and Tempostatin (phase II for bladder
cancer).
(5) (a) Kamal, A.; Reddy, K. S.; Prasad, B. R.; Babu, A. H.; Ramana,
A. V. Tetrahedron Lett. 2004, 45, 6517. (b) Larksarp, C.; Alper, H. J. Org.
Chem. 2000, 65, 2773.
(9) Rueping, M.; Antonchick, A. P.; Sugiono, E.; Grenader, K. Angew.
Chem., Int. Ed. 2009, 48, 908.
(10) (a) Baudy, R. B.; Fletcher, H., III; Yardley, J. P.; Zaleska, M. M.;
Bramlett, D. R.; Tasse, R. P.; Kowal, D. M.; Katz, A. H.; Moyer, J. A.;
Abou-Gharbia, M. J. Med. Chem. 2001, 44, 1516. (b) Hauel, N. H.; Nar, H.;
Priepke, H.; Ries, U.; Stassen, J.; Wienen, W. J. Med. Chem. 2002, 45, 1757.
DOI: 10.1021/jo100345t
r
Published on Web 04/01/2010
J. Org. Chem. 2010, 75, 3311–3316 3311
2010 American Chemical Society

Zhao et al.
JOCArticle
TABLE 1. Copper-Catalyzed Amination of 2-Bromobenzoic Acid,
2-Chlorobenzoic Acid, and N-(2-Bromophenyl)acetamide with NaN3
As the Amino Source: Optimization of Conditionsa
FIGURE 1. 2-Aminobenzoic acid, 2-aminobenzamide, and N-(2-
aminophenyl)acetamide derivatives as intermediates of some im-
portant nitrogen-containing heterocyclic compounds.
drugs,11 organic light emitting diodes (OLEDs),12 and poly-
mers.13 Among the previous methods,14 the condensation of 1,2-
diaminoarene derivatives with carbonyl compounds is perhaps
the most common.15,16 Therefore, it is very desirable to develop
readily prepared 1,2-diaminoarene derivatives (Figure 1, struc-
ture C). Recently, copper-catalyzed Ullmann N-arylations have
produced great progress,17 and the N-arylation strategy has been
used to make aryl azides.18 The wide applications of 2-amino-
benzoic acid, 2-aminobenzamide, and N-(2-aminophenyl)ace-
tamide derivatives have stimulated our research into the devel-
opment of new strategies for their synthesis. In continuation of
our endeavors to develop copper-catalyzed cross couplings,19
herein, we report a simple, convenient copper-catalyzed direct
amination of ortho-functionalized haloarenes using NaN3 as the
amino source under mild conditions.
entry substrate
cat.
CuI
CuI
CuI
CuI
ligand
base
solvent
yield (%)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
1a
1a
1a
1a
1a
1a
1a
1a
1a
1a
1a
1a
1a
1a
1a
1a
1a
1e
1e
1n
1n
1n
1n
L1
L2
L3
L4
K2CO3 C2H5OH
K2CO3 C2H5OH
K2CO3 C2H5OH
K2CO3 C2H5OH
K2CO3 C2H5OH
K2CO3 C2H5OH
K2CO3 C2H5OH
K2CO3 C2H5OH
K2CO3 C2H5OH
K2CO3 C2H5OH
Cs2CO3 C2H5OH
K3PO4 C2H5OH
Cs2CO3 CH3OH
Cs2CO3 PhCH2OH
Cs2CO3 2-propanol
Cs2CO3 tert-butanol
Cs2CO3 DMSO
73
88
68
69
83
80
62
65
CuI
CuBr
CuCl
Cu2O
Cu(OAc)2
70
trace
91
85
CuI
CuI
CuI
CuI
CuI
CuI
CuI
CuI
CuI
CuI
CuI
CuI
CuI
89
trace
trace
trace
25
51
90
0
52
45
47
Results and Discussion
Initially, 2-bromobenzoic acid was chosen as the model sub-
strate to optimize reaction conditions including the catalysts,
bases, and solvents under nitrogen atmosphere as shown in
Table 1. Interestingly, reaction of 2-bromobenzoic acid with
NaN3 in ethanol at 95 °C afforded 2-aminobenzoic acid rather
than 2-azidobenzoic acid with use of 10 mol % CuI as the
catalyst, 20 mol % of L-proline as the ligand, and 2 equiv of
K2CO3 as the base (relative to amount of 2-bromobenzoic acid)
(entry 1). Other ligands were tested (entries 2-4), and N,N0-
dimethylethylenediamine (DMEDA) was proven to be most
effective (entry 2). Reaction of 2-bromobenzoic acid with NaN3
provided 83% yield in the absence of ligand (entry 5). We
attempted various copper salts (compare entries 5-9), and CuI
Cs2CO3 C2H5OH
Cs2CO3 C2H5OH
Cs2CO3 C2H5OH
K2CO3 C2H5OH
K2CO3 C2H5OH
Cs2CO3 C2H5OH
L2
L2
L1
L2
aReaction condition: NaN3 (4 mmol), catalyst (0.1 mmol), ligand
(0.2 mmol), base (2 mmol), solvent (5 mL), reaction temperature (95 °C)
under nitrogen atmosphere, reaction time (36 h).
showed the highest activity (entry 5). No target product was
observed in the absence of copper catalyst (entry 10). The bases
were also investigated, and Cs2CO3 gave the highest yield (com-
pare entries 5, 11, and 12). Other solvents were screened (entries
13-17), ethanol was proven to be best (entry 11), and DMSO
provided 25% yield for unknown reasons (entry 17). When 2-
chlorobenzoic acid was used as the substrate, only 51% yield of
the target product was obtained under the same condition as
entry11(entry18). Thereactivity greatly increased when 20 mol
% of DMEDA was used as the ligand (entry 19). Reaction of
N-(2-bromophenyl)acetamide with NaN3 did not work under
the same condition as entry 11 (entry 20). We also attempted
different bases and ligands (compare 21-23), and a moderate
yield was provided with use of 2 equiv of K2CO3 as the base and
20 mol % of DMEDA as the ligand (entry 21). Reaction tem-
perature was also changed, and 95 °C was the best choice.
The scope of copper-catalyzed amination of the 2-haloben-
zoic acid and 2-halobenzamide derivatives was investigated with
use of NaN3 as the amino source under the optimized condi-
tions. Amination of the 2-bromobenzoic acid and 2-bromoben-
zamide derivatives was performed with 10 mol % of CuI as the
catalyst and 2 equiv of Cs2CO3 as the base. For 2-chlorobenzoic
acid and 2-chlorobenzamide derivatives (see entries 5, 6, 12,
and 13), an additional ligand, 20 mol % of DMEDA, was
required to promote their reactivity because of lower activity of
the C-Cl bond. As shown in Table 2, most of the examined
(11) VelIk, J.; Baliharova, V.; Fink-Gremmels. J.; Bull, S.; Lamka, J.;
Skalova, L. Res. Vet. Sci. 2004, 76, 95 and reference cited therein.
(12) Schwartz, G.; Fehse, K.; Pfeiffer, M.; Walzer, K.; Leo, K. Appl. Phys.
Lett. 2006, 89, 083509.
(13) Asensio, J. A.; Gomez-Romero, P. Fuel Cells 2005, 5, 336.
(14) Grimmett, M. R. In Imidazole and Benzimidazole Synthesis, Best
Synthetic methods; Meth-Cohn, O., Ed.; Academic: London, UK, 1997.
(15) (a) Meng, L.; Fettinger, J. C.; Kurth, M. J. Org. Lett. 2007, 9, 5055.
(b) Liao, Y.-L.; Lin, C.-Y.; Wong, K.-T.; Hou, T.-H.; Hung, W.-Y. Org.
Lett. 2007, 9, 4511.
(16) Fonseca, T.; Gigante, B.; Gilchrist, T. L. Tetrahedron 2001, 57, 1793.
(17) For recent reviews on copper-catalyzed cross couplings, see:
(a) Klapars, A.; Antilla, J. C.; Huang, X.; Buchwald, S. L. J. Am. Chem.
Soc. 2001, 123, 7727. (b) Ma, D.; Cai, Q. Acc. Chem. Res. 2008, 41, 1450.
(c) Kunz, K.; Scholz, U.; Ganzer, D. Synlett 2003, 2428. (d) Ley, S. V.;
Thomas, A. W. Angew. Chem., Int. Ed. 2003, 42, 5400. (e) Beletskaya, I. P.;
Cheprakov, A. V. Coord. Chem. Rev. 2004, 248, 2337. (f) Evano, G.;
Blanchard, N.; Toumi, M. Chem. Rev. 2008, 108, 3054. (g) Monnier, F.;
Taillefer, M. Angew. Chem., Int. Ed. 2009, 48, 6954 and references cited therein.
(18) (a) Zhu, W.; Ma, D. Chem. Commun. 2004, 888. (b) Andersen, J.;
Madsen, U.; Bjorkling, F.; Liang, X. Synlett 2005, 2209.
(19) For selected papers for copper-catalyzed cross couplings, see: (a) Rao,
H.; Jin, Y.; Fu, H.; Jiang, Y.; Zhao, Y. Chem.;Eur. J. 2006, 12, 3636. (b) Jiang,
D.; Fu, H.; Jiang, Y.; Zhao, Y. J. Org. Chem. 2007, 72, 672. (c) Guo, X.; Rao, H.;
Fu, H.; Jiang, Y.; Zhao, Y. Adv. Synth. Catal. 2006, 348, 2197. (d) Rao, H.; Fu,
H.; Jiang, Y.; Zhao, Y. Angew. Chem., Int. Ed. 2009, 48, 1114. (e) Yang, D.; Liu,
H.; Yang, H.; Fu, H.; Hu, L.; Jiang, Y.; Zhao, Y. Adv. Synth. Catal. 2009, 351,
1999. (f) Liu, X.; Fu, H.; Jiang, Y.; Zhao, Y. Angew. Chem., Int. Ed. 2009, 48,
348. (g) Wang, F.; Liu, H.; Fu, H.; Jiang, Y.; Zhao, Y. Org. Lett. 2009, 11, 2469.
3312 J. Org. Chem. Vol. 75, No. 10, 2010

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JOCArticle
TABLE 2. Copper-Catalyzed Synthesis of Ortho-Functionalized Aromatic Aminesa
aReaction condition: ortho-functionalized haloarene (1 mmol), NaN3 (4 mmol), CuI (0.1 mmol), Cs2CO3 (2 mmol for entries 1-13), K2CO3 (2 mmol
b
for entries 14 and 15), C2H5OH (5 mL), reaction temperature (95 °C) under nitrogen atmosphere. Addition of N,N0-dimethylethylenediamine
(0.2 mmol). cReaction temperature (78 °C).
J. Org. Chem. Vol. 75, No. 10, 2010 3313

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SCHEME 1. Treatment of 1-(4-Bromophenyl)ethanone with
NaN3 (a) and Reactions of 1-(4-Azidophenyl)ethanone (b) and
2-Azidobenzoic Acid (c) under Our Standard Conditions
SCHEME 3. (a) Treatment of 2-Bromobenzenamine (1q) with
NaN3 under Our Standard Condition and (b) Possible Mechanism
for Amination of N-(2-Bromophenyl)benzamide (1o)
SCHEME 2. Possible Formation Mechanism of 2-Aminoben-
zoic Acid
SCHEME 4. Application of the Synthesized Ortho-Functiona-
lized Aromatic Amines in Synthesis of Nitrogen-Containing
Heterocyclic Compounds
2-halobenzoic acid and 2-halobenzamide derivatives provided
good to excellent yields at 95 °C. When 2,5-dibromobenzamide
was used as the substrate, the amination selectively occurred on
the ortho-site C-Br bond of -CO-NH2, which implied an
ortho-substituent effect of the amide group.19e
To explore the amination mechanism of 2-halobenzoic acid
derivatives, the following control experiments were performed
under our standard condition as shown in Scheme 1. Reaction
of 1-(4-bromophenyl)ethanone with NaN3 did not work be-
cause of the absence of an ortho-substituent group (Scheme 1a).
Treatment of 1-(4-azidophenyl)ethanone (3a) provided product
4 in moderate yield (56%) (Scheme 1b), and the result showed
that aromatic azides could be transferred into the corresponding
aromatic amines under our standard condition. 2-Azidobenzoic
acid produced 2-aminobenzoic acid in 93% yield (Scheme 1c),
which indicated a copper-catalyzed ortho-substituent effect19f
of the carboxyl group during transformation of azide to amine.
A possible formation mechanism of 2-aminobenzoic acid deri-
vatives was proposed in Scheme 2 according to the results above.
Coordination of 2-halobenzoic acid (1) with CuI first forms I in
the presence of base (Cs2CO3). Oxidation addition of I provides
coordinate II, and exchange of X- in II with N3- of NaN3 gives
III. Reduction elimination of III leads to IV, coordination of IV
with copper gives V, and a complex of V with ethanol provides
VI. Oxidation-reduction reaction of VI in the presence of base
leads to amination product VII with leaving acetaldehyde and
N2, and the similar copper-catalyzed oxidation of alcohols to
aldehydes was previously investigated.20 Acidification of VII
affords the target product (2) with release of copper catalyst.
The amination mechanism of 2-halobenzamide derivatives could
be similar to the result above and the previous report.19e
N-(2-Bromophenyl)acetamide (1n) and N-(2-bromophe-
nyl)benzamide (1o) also provided the corresponding amination
products in moderate yields (entries 14 and 15 in Table 2) under
our catalytic condition (10 mol % of CuI as the catalyst, 2 equiv
of K2CO3 as the base, and 20 mol % of DMEDA as the ligand).
However, 2-bromobenzenamine (1q) could not react with NaN3
under the same condition (Scheme 3a), and the results showed
an ortho-substituent effect of the -NHCOPh group in 1o dur-
ing azidation as shown in Scheme 3b. Coordination of N-(2-
bromophenyl)benzamide (1o) with CuI and the following oxi-
dation addition forms I, and treatment of I with NaN3 gives II.
Reduction elimination of II affords N-(2-azidophenyl)benza-
mide (III) with leaving copper catalyst. N-(2-Azidophenyl)ben-
zamide undergoes a similar oxidation-reduction process to that
shown in Scheme 2 to give the target product (2m) under our
catalytic condition.
The amination reactions in Table 2 could tolerate various
functional groups including nitro (entries 2, 3, 6, 8, and 13),
C-Cl bond (entries 4 and 10), C-Br bond (entry 9), carboxyl
(entries 1-6), and amide (entries 7-15) in the substrates.
We attempted synthesis of some nitrogen-containing het-
erocyclic compounds by using the synthesized ortho-func-
tionalized aromatic amines as the materials as shown in
Scheme 4. Reaction of 2-amino-4-nitrobenzoic acid (2e) with
ꢀ
(20) (a) Marko, I. E.; Giles, P. R.; Tsukazaki, M.; Brown, S. M.; Urch, C.
J. Science 1996, 274, 2044. (b) Kumpulainen, E. T. T.; Koskinen, A. M. P.
Chem.;Eur. J. 2009, 15, 10901.
3314 J. Org. Chem. Vol. 75, No. 10, 2010

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JOCArticle
Ac2O afforded compound 5 in 81% yield, and the treatment
of 5 with aniline in ethanol gave 2-methyl-7-nitro-3-phenyl-
quinazolin-4(3H)-one (6) in 79% yield according to the
previous procedure (Scheme 4a).21 Reaction of 2-amino-5-
chlorobenzamide (2i) with benzoyl chloride provided 7, and
treatment of 7 in 5% NaOH aqueous solution afforded 6-
chloro-2-phenylquinazolin-4(3H)-one (8) in 73% total yield
(Scheme 4b).22 Reaction of 2-amino-5-nitrobenzamide (2k)
with benzaldehyde in the presence of CF3COOH produced
the corresponding dihydroquinazolinone (9) in 72% yield
(Scheme 4c).23 Treatment of N-(2-aminophenyl)acetamide
(2l) in acetic acid afforded 2-methyl-1H-benzoimidazole (10)
in 90% yield (Scheme 4d).15c
product. For 2-halobenzamide or N-(2-bromophenyl)acetamide
derivative substrtates, the resulting solution was filtered, and the
solid was washed with ethanol. The combined ethanol solution was
concentrated, and the residue was purified by column chromatog-
raphy on silica gel to provide the desired product.
2-Aminobenzoic acid (2a).24 Eluent: petroleum ether/ethyl
acetate (2:1). Yield: 125 mg (91%), using 2-bromobenzoic acid
as the substrate; 123 mg (90%), using 2-chlorobenzoic acid as
1
the substrate. Yellow solid, mp 145 °C (lit.24 mp 145 °C). H
NMR (DMSO-d6, 300 MHz) δ 8.59 (s, br, 2H), 7.68 (d, 1H, J =
7.9 Hz), 7.22 (t, 1H, J = 7.5 Hz), 6.76 (d, 1H, J = 8.2 Hz), 6.50 (t,
1H, J = 7.2 Hz). 13C NMR (DMSO-d6, 75 MHz) δ 170.1, 152.0,
134.3, 131.7, 116.8, 115.1, 110.1. ESIMS [M þ H]þ m/z 138.1.
2-Amino-5-nitrobenzoic acid (2b).25 Eluent: petroleum ether/
ethyl acetate (2:1). Yield: 144 mg, 79%. Yellow solid, mp 278 °C
(lit.25 mp 279-280 °C, dec). 1H NMR (DMSO-d6, 300 MHz) δ
13.32 (s, br, 1H), 8.60 (d, 1H, J = 2.2 Hz), 8.08 (d, 1H, J = 9.3
Hz), 7.88 (s, br, 2H), 6.88 (d, 1H, J = 9.3 Hz). 13C NMR
(DMSO-d6, 75 MHz) δ 168.1, 156.1, 135.0, 128.7, 128.6, 116.5,
108.5. ESIMS [M þ H]þ m/z 183.1.
Conclusion
We have developed a simple copper-catalyzed amination of
o-functionalized haloarenes (2-halobenzoic acid, 2-halobenza-
mide, and N-(2-bromophenyl)acetamide derivatives) using
NaN3 as the amino source in ethanol, and the corresponding
2-aminobenzoic acid, 2-aminobenzamide, and N-(2-aminophe-
nyl)acetamide derivatives were obtained in good to excellent
yields. The protocol undergoes one-pot Ullmann-type coupling
of ortho-functionalized haloarenes with NaN3 to give ortho-
functionalized azidoarenes, followed reduction with ethanol,
and ethanol acted as solvent and reductive agent. The method is
of economical and practical advantages, and the synthesized
compounds can be widely used in the synthesis of various
nitrogen-containing heterocyclic compounds.
2-Amino-3-nitrobenzoic acid (2c).26 Eluent: petroleum ether/
ethyl acetate (1:2). Yield: 174 mg (95%). Yellow solid, mp
209 °C (lit.26 mp 208 -209 °C). 1H NMR (DMSO-d6, 300 MHz)
δ 13.46 (s, br, 1H), 8.51 (s, br, 2H), 8.30 (d, 1H, J = 8.3 Hz), 8.23
(d, 1H, J = 7.7 Hz), 6.72 (t, 1H, J = 8.1 Hz). 13C NMR (DMSO-
d6, 75 MHz) δ 168.7, 146.8, 139.7, 132.5, 131.7, 114.8, 113.9.
ESIMS [M þ H]þ m/z 183.1.
2-Amino-5-chlorobenzoic acid (2d).27 Eluent: petroleum ether/
ethyl acetate (2:1). Yield: 133 mg (77%). Pale yellow crystal, mp
204 °C (lit.27 mp 204 °C). 1H NMR (DMSO-d6, 300 MHz) δ 8.78
(s, br, 2H), 7.61 (d, 1H, J = 2.0 Hz), 7.24 (d, 1H, J = 8.9 Hz),
6.77 (d, 1H, J = 8.9 Hz). 13C NMR (DMSO-d6, 75 MHz) δ
169.0, 150.8, 134.0, 130.4, 118.8, 118.0, 110.9. ESIMS [M þ H]þ
m/z 172.1.
Experimental Section
2-Amino-4-nitrobenzoic acid (2e).28 Eluent: petroleum ether/
ethyl acetate (2:1). Yield: 113 mg 62%. Yellow solid, mp 264 °C
(lit.28 mp 264 °C). 1H NMR (DMSO-d6, 300 MHz) δ 7.93 (d, 1H,
J = 8.3 Hz), 7.44 (d, 1H, J = 1.7 Hz), 7.33 (s, br, 2H), 7.16 (d,
1H, J = 8.2 Hz). 13C NMR (DMSO-d6, 75 MHz) δ 171.0, 151.3,
149.2, 133.3, 125.3, 109.5, 108.1. ESIMS [M þ H]þ m/z 183.1.
2-Aminobenzamide (2f).29 Eluent: petroleum ether/ethyl acet-
ate (2:1). Yield: 108 mg (79%) with 2-bromobenzamide as the
substrate; 96 mg (70%) with 2-chlorobenzamide as the sub-
strate. White crystal, mp 110 °C (lit.29 mp 109-110 °C). 1H
NMR (DMSO-d6, 300 MHz) δ 7.71 (s, br, 1H), 7.52 (d, 1H, J =
7.6 Hz), 7.12 (t, 1H, J = 7.6 Hz), 7.04 (s, br, 1H), 6.67 (d, 1H,
J = 7.9 Hz), 6.55 (s, br, 2H), 6.46 (t, 1H, J = 7.4 Hz). 13C NMR
(DMSO-d6, 75 MHz) δ 171.3, 150.2, 131.9, 128.7, 116.4, 114.4,
113.7. ESIMS [M þ H]þ m/z 137.2.
General Experimental Procedures. All reactions were carried
out under nitrogen atmosphere in sealed tubes. Proton and
carbon magnetic resonance spectra (1H NMR and 13C NMR)
were recorded with tetramethylsilane (TMS) in the solvent of
CDCl3 as the internal standard (1H NMR: TMS at 0.00 ppm,
CHCl3 at 7.24 ppm; 13C NMR: CDCl3 at 77.0 ppm) or were
recorded with tetramethylsilane (TMS) in the solvent of DMSO-
d6 as the internal standard (1H NMR: TMS at 0.00 ppm, DMSO
at 2.50 ppm; 13C NMR: DMSO at 40.0 ppm).
General Procedure for Synthesis of Compounds 2a-m. A 10 mL
Schlenk tube equipped with a magnetic stirring bar was charged
with CuI (0.1 mmol, 19 mg), NaN3 (4 mmol, 260 mg), Cs2CO3
(2 mmol, 652 mg for entries 1-13 in Table 2) or K2CO3 (2 mmol,
276 mg for entries 14 and 15 in Table 2), and 2-halobenzoic acid,
2-halobenzamide, or N-(2-bromophenyl)acetamide derivative
(1 mmol). The tube was evacuated twice and backfilled with nitro-
gen. Ethanol (5 mL) and N,N0-dimethylethylenediamine (DME-
DA) (0.2 mmol, 18 mg for entries 5, 6, 12, 13, 14, and 15 in Table 2)
were sequentially added at room temperature under a stream of
nitrogen, and the tube was sealed and put into a preheated oil bath
at 95 °C for 12-56 h under a positive pressure of nitrogen. After
the resulting solution was cooled to room temperature, the solvent
was removed under rotary evaporation. Five milliliters of HCl
(1 N) was added to acidify the solution (pH 2-3), and the solution
was extracted with ethyl acetate (3 ꢀ 5 mL) for 2-halobenzoic acid
derivative substrates (entries 1-6 in Table 2). The combined
organic phase was concentrated, and the residue was purified by
column chromatography on silica gel to provide the desired
2-Amino-3-nitrobenzamide (2g).26 Eluent: petroleum ether/
ethyl acetate (1:1). Yield: 128 mg (71%). Yellow solid, mp
1
237 °C (lit.26 mp 234 °C). H NMR (DMSO-d6, 300 MHz) δ
8.49 (s, br, 2H), 8.19 (d, 1H, J = 8.6 Hz), 8.16 (s, br, 1H), 7.96 (d,
1H, J = 7.6 Hz), 7.63 (s, br, 1H), 6.69 (t, 1H, J = 7.9 Hz). 13
C
NMR (DMSO-d6, 75 MHz) δ 170.0, 146.1, 136.4, 132.1, 129.4,
118.8, 113.7. ESIMS [M þ H]þ m/z 182.1.
2-Amino-5-bromobenzamide (2h).30 Eluent: petroleum ether/
ethyl acetate (2:1). Yield: 138 mg (64%). White solid, mp 188 °C
(24) Grover, G.; Kini, S. G. Eur. J. Med. Chem. 2006, 41, 256.
(25) Makosza, M.-l.; Bia-lecki, M. J. Org. Chem. 1998, 63, 4878.
(26) White, A. W.; Almassy, R.; Calvert, A. H.; Curtin, N. J.; Griffin, R.
J.; Hostomsky, Z.; Maegley, K.; Newell, D. R.; Srinivasan, S.; Golding, B. T.
J. Med. Chem. 2000, 43, 4084.
(21) Kislyi, K. A.; Samet, A. V.; Strelenko, Y. A.; Semenov, V. V. J. Org.
Chem. 2008, 73, 2285.
(22) Fleming, W. J.; Muller-Bunz, H.; Lillo, V.; Fernandez, E.; Guiry, P.
J. Org. Biomol. Chem. 2009, 7, 2520.
(27) Bergmann, E. D.; Berkovic, S. J. Org. Chem. 1961, 26, 919.
(28) Joshi, S. S.; Gambhir, I. R. J. Am. Chem. Soc. 1956, 78, 2222.
(29) Kijima, M.; Nambu, Y.; Endo, T.; Okawara, M. J. Org. Chem. 1984,
49, 1434.
(23) Paige, M.; Grindrod, S.; Hamel, E.; Dakshanamurthy, S.; Chruszcz,
M.; Minor, W.; Brown, M. L. J. Med. Chem. 2008, 51, 4620.
(30) Cheng, X.; Vellalath, S.; Goddard, R.; List, B. J. Am. Chem. Soc.
2008, 130, 15786.
J. Org. Chem. Vol. 75, No. 10, 2010 3315

Zhao et al.
JOCArticle
(lit.30 mp 187-189 °C). 1H NMR (DMSO-d6, 300 MHz) δ 7.85
(s, br, 1H), 7.70 (d, 1H, J = 2.1 Hz), 7.25 (d, 1H, J = 8.9 Hz),
Yield: 180 mg (64%) of a mild yellow powder, mp 207-210 °C
(lit.35 mp 205-207 °C). 1HNMR(CDCl3, 300MHz) δ8.49 (s, 1H),
8.41 (d, 1H, J = 8.6 Hz), 8.20 (d, 1H, J = 8.6 Hz), 7.55-7.60 (m,
3H), 7.29 (d, 2H, J = 7.6 Hz), 2.29 (s, 3H). 13C NMR (CDCl3, 75
MHz) δ 161.2, 156.9, 151.8, 148.1, 137.1, 130.4, 129.9, 129.3, 129.1,
127.8, 125.0, 122.6, 120.3, 24.6. ESIMS [M þ H]þ m/z 282.1.
6-Chloro-2-phenylquinazolin-4(3H)-one (8).22 To a solution
of 2-amino-5-chlorobenzamide (1 mmol, 170 mg) and pyridine (1.2
mmol, 95 mg) in dichloromethane (3 mL) was added benzoyl chlo-
ride (1.2 mmol, 168 mg) slowly via syringe then the solution was
stirred for 1 h at room temperature. The pale yellow solid formed
was filtered and taken up in a solution of aqueous NaOH (5%,
3 mL) and refluxed for 30 min. The solution was cooled to room
temperature and acidified to pH ∼3 with HCl (1 M). The solid was
filtered and washed with water to yield the title compound as a
white fibrous solid.22 Total yield 187 mg (73%), mp 288 °C (lit.19f
mp 286-288 °C). 1H NMR (DMSO-d6, 600 MHz) δ 12.75 (s, 1H),
8.18 (d, 2H, J =7.6 Hz), 8.09 (s, 1H), 7.87 (d, 1H, J = 2.8 Hz), 7.78
(d, 1H, J = 7.1 Hz), 7.56-7.61 (m, 3H). 13C NMR (DMSO-d6 150
MHz) δ 161.8, 153.3, 148.0, 135.2, 133.0, 132.1, 131.3, 130.2, 129.1,
128.4, 125.4, 122.7. ESIMS [M þ H]þ m/z 257.3.
7.17 (s, br, 1H), 6.72 (s, br, 2H), 6.66 (d, 1H, J = 8.6 Hz). 13
C
NMR (DMSO-d6, 75 MHz) δ 170.5, 149.9, 134.8, 131.3, 119.0,
115.7, 105.2. ESIMS [M þ H]þ m/z 214.1, 216.1.
2-Amino-5-chlorobenzamide (2i).31 Eluent: petroleum ether/
ethyl acetate (2:1). Yield: 112 mg (66%). White solid, mp 174 °C.
1H NMR (DMSO-d6, 300 MHz) δ 7.88 (s, br, 1H), 7.61 (d, 1H,
J = 2.1 Hz), 7.14-7.22 (m, 2H), 6.71-6.74 (m, 3H). 13C NMR
(DMSO-d6, 75 MHz) δ170.6, 149.6, 132.1, 128.5, 118.6, 118.0,
115.0. ESIMS [M þ H]þ 171.2.
2-Amino-4-methylbenzamide (2j).6b Eluent: petroleum ether/
ethyl acetate (2:1). Yield: 98 mg (65%). White solid, mp 148 °C. 1H
NMR (DMSO-d6, 300 MHz) δ 7.67 (s, br, 1H), 7.44 (d, 1H, J =
6.12 Hz), 6.94 (s, 1H), 6.56 (s, 2H), 6.47 (s, 1H), 6.28 (d, 1H, J=6.12
Hz), 2.16 (s, 3H). 13C NMR (DMSO-d6, 75 MHz) δ 171.8, 150.9,
142.1, 129.4, 117.0, 116.1, 111.6, 21.6. ESIMS [M þ H]þ 151.2.
2-Amino-4-nitrobenzamide (2k).32 Eluent: petroleum ether/
ethyl acetate (1:1). Yield: 77 mg (43%). Yellow solid, mp
222-224 °C (lit.32 mp 221-223 °C dec). 1H NMR (DMSO-d6,
300 MHz) δ 8.06 (s, br, 1H), 7.74 (d, 1H, J = 8.6 Hz), 7.57 (d, 1H,
J = 2.4 Hz), 7.47 (s, br, 1H), 7.24 (d, 1H, J = 8.6 Hz), 7.03 (s, br,
2H). 13C NMR (DMSO-d6, 75 MHz) δ 170.2, 151.2, 150.0, 130.8,
119.3, 110.7, 108.4. ESIMS [M þ H]þ 182.3.
2,3-Dihydro-7-nitro-2-phenyl-4(1H)-Quinazolinone (9).23 To
a room temperature solution of 4-nitroanthranilamide (1.19
mmol, 182 mg) and benzaldehyde (1.19 mmol, 106 mg) in 8 mL
of MeCN was added 1-2 drops of trifluoroacetic acid. After
the solution was stirred for 24 h at room temperature, the
precipitate was collected and recrystallized from THF-hexanes
to give 9 as a yellow solid. Yield 195 mg (72%), mp 220 °C (lit.23
mp 219-221 °C). 1H NMR (DMSO-d6, 600 MHz) δ 8.71
(s, 1H), 7.91 (s, 1H), 7.83 (d, H, J = 8.2 Hz), 7.62 (d, 1H, J =
2.0 Hz), 7.49 (d, 2H, J = 7.6 Hz), 7.43-7.36 (m, 4H), 5.91
(s, 1H). 13C NMR (DMSO-d6, 150 MHz) δ 162.3, 151.3, 148.7,
141.8, 129.6, 129.2, 129.0, 127.2, 119.7, 111.4, 109.4, 66.8.
ESIMS [M þ H]þ m/z 270.1.
N-Acetyl-2-aminoaniline (2l).33 Eluent: petroleum ether/ethyl
acetate (1:2). Yield: 78 mg (52%). White solid, mp 128 °C (lit.33
mp 130 °C). 1H NMR (DMSO-d6, 300 MHz) δ 9.11 (s, 1H), 7.15
(d, 1H, J = 7.9 Hz), 6.88 (t, 1H, J = 8.4 Hz), 6.70 (d, 1H, J = 7.9
Hz), 6.53 (t, 1H, J = 8.2 Hz), 4.88 (s, br, 2H), 2.03 (s, 3H). 13
C
NMR (DMSO-d6, 75 MHz) δ 168.7, 142.4, 126.3, 125.9, 124.1,
116.7, 116.3, 23.8. ESIMS [M þ H]þ m/z 151.1.
N-(2-Aminophenyl)benzamide (2m).34 Eluent: petroleum
ether/ethyl acetate (1:1). Yield: 145 mg (68%). White solid,
mp 149-151 °C (lit.34 mp 148 °C). H NMR (DMSO-d6, 300
1
MHz) δ 9.68 (s, 1H), 8.00 (d, 2H, J = 7.2 Hz), 7.50-7.57 (m,
3H), 7.19 (d, 1H, J = 7.6 Hz), 6.97 (t, 1H, J = 7.5 Hz), 6.80 (d,
1H, J = 7.9 Hz), 6.61 (t, 1H, J = 7.5 Hz), 4.91 (s, 2H). 13C NMR
(DMSO-d6, 75 MHz) δ 165.9, 143.7, 135.2, 131.9, 128.8, 128.3,
127.2, 127.0, 123.9, 116.8, 116.7. ESIMS [M þ H]þ m/z 213.2.
4-Aminoacetophenone (4).29 Eluent: petroleum ether/ethyl
acetate (5:1). Yield: 75 mg (56%). White solid, mp 104 °C
(lit.29 mp 104-106 °C) .1H NMR (CDCl3, 300 MHz) δ 7.79
(d, 2H, J = 8.6 Hz), 6.63 (d, 2H, J = 8.6 Hz), 4.21 (s, br, 2H),
2.49 (s, 3H). 13C NMR (CDCl3, 75 MHz) δ 196.7, 151.5, 130.9,
127.7, 113.8, 26.2. ESIMS [M þ H]þ m/z 136.1.
2-Methyl-1H-benzimidazole (10).16 A mixture of the N-acet-
yl-2-aminoaniline (0.5 mmol, 75 mg), xylene (4 mL), and acetic
acid (1.5 mL) was refluxed for 15 min. The solution was
evaporated to dryness, the residue was purified by silica gel
column chromatography with dichloromethane/methanol
(9.5:0.5) as eluent, and 2-methyl-1H-benzimidazole (60 mg,
1
90%) was obtained.16 Mp 177 °C (lit.36 mp 175-176 °C). H
NMR (CDCl3, 600 MHz) δ 10.98 (s, br, 1H), 7.55-7.57 (m, 2H),
7.21-7.23 (m, 2H), 2.66 (s, 3H). 13C NMR (CDCl3, 150 MHz) δ
151.4, 138.7, 122.3, 114.6, 15.0. ESIMS [M þ H]þ m/z 133.1.
2-Methyl-3-phenyl-7-nitro-4(3H)-quinazolinone (6).35 A sus-
pension of 4-nitroanthranilic acid (364 mg, 2.0 mmol) was refluxed
in Ac2O (4 mL) for 1 h. The resulting solution was concentrated
with the aid of a rotary evaporator, and the residue was added to a
solution of aniline (2 mmol) in EtOH (4 mL) under vigorous
stirring. The mixture was refluxed for 40 min, and then the solvent
was evaporated to dryness. Water (10 mL) was added, and the
insoluble residue was filtered off, washed with water, and dried.21
Acknowledgment. Financial support was provided by the
National Natural Science Foundation of China (Grant Nos.
20672065, 20732004, 20872010, and 20972083), Chinese 863
Project (Grant Nos. 2007AA02Z160 and 2006DFA43030),
and the Key Subject Foundation from Beijing Department
of Education (XK100030514).
Supporting Information Available: 1H, 13C NMR spectra of
all synthesized compounds. This material is available free of
charge via the Internet at http://pubs.acs.org.
(31) Blackie, J. A.; Turner, N.; Wells, A. Tetrahedron Lett. 1997, 38, 3043.
(32) Nakayama, H.; Nozawa, M.; Kanaoka, Y. Chem. Pharm. Bull. 1979,
27, 2775.
(33) Eshghi, H.; Gordi, Z. Synth. Commun. 2003, 33, 2971.
(34) Deka, D. C.; Kakati, H. S. J. Chem. Res. 2006, 223.
(35) Taniyama, H.; Yasui, B.; Uchida, H.; Okuda, Y. Yakugaku Zasshi
1961, 81, 431.
(36) van den Berg, D.; Zoellner, K. R.; Ogunrombi, M. O.; Malan, S. F.;
ꢀ
TerreBlanche, G.; Castagnoli, N.; Bergh, J. J.; Petzer, J. P. Bioorg. Med.
Chem. 2007, 15, 3692.
3316 J. Org. Chem. Vol. 75, No. 10, 2010