Palladium-catalyzed ortho-acylation of 2-arylbenzoxazoles and 2-arylbenzothiazoles using arylmethyl alcohols as the acyl source

Article abstract of DOI:10.1016/j.tet.2013.04.052

A facile and efficient way for the synthesis of the acylated 2-arylbenzoxazoles and 2-arylbenzothiazoles by heterocycle-directed ortho-acylation was developed. This reaction was performed in chlorobenzene, using arylmethyl alcohols and tert-butyl hydroperoxide (TBHP) as the easily accessible acyl source and the oxidant, respectively, affording the desired products in moderate to good yields.

Full text of DOI:10.1016/j.tet.2013.04.052

Tetrahedron 69 (2013) 4908e4914
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Palladium-catalyzed ortho-acylation of 2-arylbenzoxazoles and
2-arylbenzothiazoles using arylmethyl alcohols as the acyl source
*
*
Qian Zhang, Fan Yang , Yangjie Wu
The College of Chemistry and Molecular Engineering, Henan Key Laboratory of Chemical Biology and Organic Chemistry, Key Laboratory of Applied
Chemistry of Henan Universities, Zhengzhou University, Zhengzhou 450052, People’s Republic of China
a r t i c l e i n f o
a b s t r a c t
Article history:
A facile and efficient way for the synthesis of the acylated 2-arylbenzoxazoles and 2-arylbenzothiazoles
by heterocycle-directed ortho-acylation was developed. This reaction was performed in chlorobenzene,
using arylmethyl alcohols and tert-butyl hydroperoxide (TBHP) as the easily accessible acyl source and
the oxidant, respectively, affording the desired products in moderate to good yields.
Ó 2013 Elsevier Ltd. All rights reserved.
Received 1 February 2013
Received in revised form 25 March 2013
Accepted 11 April 2013
Available online 17 April 2013
Keywords:
Acylation
2-Arylbenzoxazole
CeH activation
Arylmethyl alcohol
1. Introduction
source would be environmentally friendly, naturally abundant,
stable, commercially available, and easy to handle. However, the
Aryl ketones are important subunits or skeleton in the phar-
maceutical intermediates, dyes, some bioactive compounds and
functional materials.1 The classical FriedeleCrafts reaction has been
the main method of acylation for quite a long time, which suffers
from poor regioselectivity and harsh reaction conditions.2 In the
past few years, transition metal-catalyzed ortho-CeH bond func-
tionalization has become an important and reliable tool in the or-
ganic synthesis.3 Especially, when the CeH bond was adjacent to
a directing group, this CeH bond activation showed unique re-
activity with high regioselectivity.4 Thus, the acylation through the
direct CeH bond functionalization protocol would be an area suf-
ficient with research interests. During recent years, great progress
on the transition metal-catalyzed ortho-CeH bond acylation using
aldehydes as the acyl source has been achieved in several groups,
such as Cheng, Li, Yu, and Kwong.5 However, aldehydes also have
their own limitations, for example, higher toxicities and lower
environmentally friendly properties. To overcome these problems,
in 2011, Li and co-workers for the first time reported that
palladium-catalyzed acylation of 2-arylpyridines with alcohols as
acyl source.6a Meanwhile, Wang’s group also reported palladium-
catalyzed oxidative CeH bond acylation of acetanilides with ben-
zylic alcohols.6b In this reaction, arylmethyl alcohols as an acyl
scope of the synthetic strategy is still relatively limited and should
be extended and investigated further.
In recent years, our research interest has been focused on the
construction of aromatic heterocycles, such as benzoxazoles and
other benzoheterocycles, some of which are key subunits or phar-
macophores in pharmaceutical chemistry and behave with low
toxicities and lots of biological activities.7 We have realized the
catalytic ligand-directed ortho-arylation, halogenations, and ace-
toxylation of 2-arylbenzoxazoles.8aed In 2012, we also developed
palladium-catalyzed ortho-acylation of 2-arylbenzoxazoles using
aldehyde as an acyl source.8e In this work, we would explore
the possibility of direct acylation of 2-arylbenzoxazoles and 2-
arylbenzothiazoles using arylmethyl alcohols as the environmen-
tal benign acyl source.
2. Results and discussion
After the initial optimized conditions of the acylation of 2-(3-
methylphenyl)benzoxazole (1a) with benzyl alcohol (2a) were
screened on oxidants (e.g., O2, BQ, DDQ, Ag2O, Cu(OAc)2, and TBHP)
and ligands (e.g., PPh3, dppf, and DavePhos), we found that TBHP
gave the best result and the ligands had no effect on this reaction
(please see SI). In the absence of any ligand, this reaction was per-
formed in toluene using 6 equivof TBHP as the oxidant, affording the
acylated product in 42% isolated yield (Table 1, entry 1). Then, the
solvent effects (e.g., bromobenzene, DCE, CH3COOH, DMSO, and
* Corresponding authors. Tel./fax: þ86 371 6797 9408; e-mail addresses: yangf@
zzu.edu.cn (F. Yang), wyj@zzu.edu.cn (Y. Wu).
0040-4020/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tet.2013.04.052

Q. Zhang et al. / Tetrahedron 69 (2013) 4908e4914
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Table 1
Effects on the acylation of 2-(3-methyphenyl)benzoxazolea
Entry
Palladium source
Oxidant (equiv)
Solvent
Yield (%)b
1
2
3
4
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(CH3CN)2Cl2
Pd2(dba)3
PdCl2
TBHP (6)
TBHP (6)
TBHP (6)
TBHP (6)
TBHP (6)
TBHP (6)
TBHP (6)
TBHP (9)
TBHP (12)
TBHP (12)
TBHP (6)
TBHP (6)
TBHP (6)
Toluene
Bromobenzene
DCE
CH3COOH
DMSO
58 (42)
10
<5
30
11
5c
6c
7
DMF
<5
Chlorobenzene
Chlorobenzene
Chlorobenzene
Chlorobenzene
Chlorobenzene
Chlorobenzene
Chlorobenzene
71 (55)
90 (76)
78 (58)
63 (45)
39
8
9
10d
11
12
13
54
17
Bold represents the optimal conditions.
a
Reaction conditions: 1a (0.3 mmol), 2a (0.6 mmol), catalyst (10 mol % of palladium source), and TBHP in solvent (2.0 mL) at refluxing temperature for 8 h.
GC yield (isolated yield) based on the amount of 2-(3-methyphenyl)benzoxazole.
At 140 ꢀC.
b
c
d
Under palladium source loading of 5 mol %.
DMF) were investigated, and when chlorobenzene was used as the
products than those bearing an electron-withdrawing group.
Comparatively, under the same reaction conditions, the acylation of
2-arylbenzothiazoles would afford the desired products in rela-
tively lower yields than those of 2-arylbenzoxazoles (Tables 2
and 3).
Besides the 2-arylbenzoxazoles and 2-arylbenzothiazoles, acyl-
ation of two other types of heterocycles, such as 2-
arylbenzimidazole (1j) and benzo[h]quinoline (1k) were also ex-
plored (Scheme 2). However, the acylation of N-methyl-2-(3-
methylphenyl)benzimidazole (1j) with p-chlorobenzyl alcohol
(2e) could not occur. Remarkably, the acylation of benzo[h]quino-
line (1k) with p-chlorobenzyl alcohol (2e) could generate the de-
sired product (4b) in up to 91% yield.
solvent, the isolated yield could be improved to 55% (Table 1, entries
2e7). It should be noted that when the oxidant loading of TBHP
increased from 6 equiv to 9 equiv, the isolated yield could increase to
76% (Table 1, entries 7 and 8). However, when the oxidant loading
was continuously enhanced to 12 equiv or the catalyst loading de-
creased to 5 mol %, lower isolated yields of 58% and 45% were ob-
tained, respectively (Table 1, entries 9 and 10). Finally, the other
palladium sources were also checked, such as Pd(CH3CN)2Cl2,
Pd2(dba)3, and PdCl2, and the desired product was observed in GC
yields of 39%, 54%, and 17%, respectively (Table 1, entries 11e13).
With the optimized conditions in hand, the acylation of 2-
arylbenzoxazoles with arylmethyl alcohols was explored, and the
results were shown in Table 2. In general, electronic effect has
significant influence on this reaction, and the substrates bearing an
electron-donating group either in the arylmethyl alcohols or the
benzene rings of 2-arylbenzoxazoles would afford higher yields of
the desired products than those bearing an electron-withdrawing
group (Table 2). It should be noted that when there was a chloro
atom in benzene ring of arylmethyl alcohol, the desired product
was obtained in the best yield of 86% (3e). Moreover, this acylation
could tolerate various functional groups, such as MeO, Cl, and Br in
the arylmethyl alcohols and Cl and F on the benzene rings of 2-
arylbenzoxazoles. To our delight, the heterocyclic group also
could be tolerated very well in this reaction, such as 2-
thiophenemethanol (2h), and the desired product was obtained
in a moderate yield of 50% (3h). In addition, the benzo ring of
benzoxazole moiety contained a methyl group or chloro atom (1g
or 1h), affording the acylated products in relatively lower yields
(Scheme 1).
3. Conclusions
We have developed a general and efficient way for the acylation
of several types of benzoheterocycles, such as 2-arylbenzoxazoles,
2-arylbenzothiazoles, and benzo[h]quinoline. This protocol not
only provides a facile synthetic route to acylated benzoxazoles and
benzothiazoles with low toxicities and potential lots of biological
activities, but also utilizes the arylmethyl alcohols as the environ-
mentally friendly, naturally abundant, stable and commercially
available acyl source. Further application of this synthetic meth-
odology is currently underway in our laboratory.
4. Experimental section
4.1. General details
With the optimized conditions, the acylation of 2-
arylbenzothiazoles with arylmethyl alcohols were also presented
in Table 3, and the corresponding products were obtained in
moderate yields. Generally, this reaction gave a similar result to
that of 2-arylbenzoxazoles, and the substrates bearing an electron-
donating group would afford the higher yields of the desired
1H NMR, 13C NMR spectra were recorded on a Bruker DPX-400
spectrometer with CDCl3 as the solvent and TMS as an internal
standard. IR spectra were recorded on a Bruker ALPHA spectrom-
eter. Melting points were measured by using a WC-1 microscopic
apparatus. GC analysis was performed on Agilent 4890D gas
chromatograph. Mass spectra were measured on an LC-MSD-Trap-

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Q. Zhang et al. / Tetrahedron 69 (2013) 4908e4914
Table 2
The palladium-catalyzed acylation of 2-arylbenzoxazolesa
Entry
R1
R2
Product
Yield (%)b
1
m-Me (1a)
p-MeC6H4 (2b)
67 (3b)
2
m-Me (1a)
p-OMeC6H4 (2c)
70 (3c)
3
m-Me (1a)
m,p-diMeO C6H3 (2d)
72 (3d)
4
m-Me (1a)
p-ClC6H4 (2e)
86 (3e)
5
m-Me (1a)
o,p-diCl C6H3 (2f)
59 (3f)
6
m-Me (1a)
p-BrC6H4 (2g)
59 (3g)

Q. Zhang et al. / Tetrahedron 69 (2013) 4908e4914
4911
Table 2 (continued )
Entry
R1
R2
Product
Yield (%)b
7
m-Me (1a)
2-Thienyl (2h)
50 (3h)
8
o-Me (1b)
p-Me (1c)
H (1d)
p-ClC6H4 (2e)
p-ClC6H4 (2e)
p-ClC6H4 (2e)
p-ClC6H4 (2e)
78 (3i)
65 (3j)
57 (3k)
52 (3l)
9
10
11
p-Cl (1e)
12
m-F (1e)
p-ClC6H4 (2e)
50 (3m)
13
p-F (1f)
p-ClC6H4 (2e)
45 (3n)
a
Reaction conditions: 1 (0.3 mmol), 2 (0.6 mmol), Pd(OAc)2 (10 mol %), TBHP (2.7 mmol) in chlorobenzene (2.0 mL) at refluxing temperature for 8 h.
Isolated yield based on the amount of 2-arylbenzoxazole.
b
XCT instrument. High resolution mass spectra were measured on
a UHPLC Q-TOF HR-MS. The single crystal X-ray diffraction study
was measured on Xcalibur, Eos, Gemini diffractometer.
Dichloromethane, ethyl acetate, and hexane were used for column
chromatography without further purification, and other solvents
were purified according to the standard methods. 2-
Arylbenzoxazoles and 2-arylbenzothiazoles were prepared
according to the reported literature.8 Other chemicals were ob-
tained from commercial sources and used as-received unless oth-
erwise noted.
a

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Q. Zhang et al. / Tetrahedron 69 (2013) 4908e4914
Scheme 1. Acylation of 2-arylbenzoxazoles bearing a substituent at the benzo ring.
Table 3
The palladium-catalyzed acylation of 2-(3-methylphenyl)benzothiazolea
Entry
R2
Product
Yield (%)b
1
p-Me (2b)
65 (3q)
2
p-OMe (2c)
73 (3r)
3
H (2a)
65 (3s)

Q. Zhang et al. / Tetrahedron 69 (2013) 4908e4914
4913
Table 3 (continued )
Entry
R2
Product
Yield (%)b
4
p-Cl (2e)
78 (3t)
5
o,p-DiCl (2f)
55 (3u)
6
p-Br (2g)
51 (3v)
a
Reaction conditions: 1i (0.3 mmol), 2 (0.6 mmol), Pd(OAc)2 (10 mol %), TBHP (2.7 mmol) in chlorobenzene (2.0 mL) at refluxing temperature for 8 h.
Isolated yield based on the amount of 2-arylbenzothiazole.
b
Scheme 2. Acylation of two other types of heterocycles.
4.2. Typical procedure for the palladium-catalyzed acylation
vacuo, the residue was purified by column chromatography (ethyl
of 2-arylbenzoxazoles
acetate/hexane) to afford the pure product.
To a solution of 2-arylbenzoxazole (0.3 mmol) in chlorobenzene
(2 mL), arylmethyl alcohol (0.6 mmol), Pd(OAc)2 (10 mol %) and
TBHP (2.7 mmol) were added. The resulting mixture was heated at
refluxing temperature for 8 h. After the reaction was complete, the
mixture was added into H2O (25 mL) and extracted with ethyl ac-
etate (10 mL) for three times. The combined organic layer was dried
over anhydrous Na2SO4 and filtered. After removal of the solvent in
4.2.1. 2-{[5-Methyl-2-(2-thenoyl)]phenyl}benzoxazole
(3h). Light
2.46 (s,
yellow solid, mp 173e176 ꢀC; 1H NMR (400 MHz, CDCl3):
d
3H), 6.87 (t, J¼4.32 Hz, 1H), 7.18e7.22 (m, 3H), 7.31e7.39 (m, 2H),
7.44 (d, J¼7.80 Hz, 1H), 7.52 (d, J¼4.88 Hz, 1H), 7.58e7.62 (m, 1H),
8.05 (s, 1H); 13C NMR (100 MHz, CDCl3):
d 21.3, 110.6, 120.3, 124.5,
125.2, 127.9, 128.6, 129.7, 130.1, 131.7, 134.4, 137.0, 140.8, 141.7, 144.9,
150.7, 151.4, 161.7, 189.2; IR (cmꢁ1): 3114, 1643, 1407, 1295, 753;

4914
Q. Zhang et al. / Tetrahedron 69 (2013) 4908e4914
HRMS-ESI (m/z): calcd for C19H14NO2S (MþH): 320.0740, found
825, 755; HRMS-ESI (m/z): calcd for
398.0173, found 398.0175.
C21H14Cl2NOS (MþH):
320.0745.
4.2.2. 2-{[4-Chloro-2-(4-chlorobenzoyl)]phenyl}benzoxazole
4.2.8. 2-{[2-(4-Bromobenzoyl)-5-methyl]phenyl}benzothiazole
(3l). Yellow solid, mp 180e182 ꢀC; 1H NMR (400 MHz, CDCl3):
(3v). Yellow solid, mp 114e117 ꢀC; 1H NMR (400 MHz, CDCl3):
d
7.18e7.21 (m, 2H), 7.26e7.32 (m, 3H), 7.40 (d, J¼1.44 Hz, 1H),
d
2.53 (s, 3H), 7.29e7.42 (m, 6H), 7.61 (d, J¼8.40 Hz, 2H), 7.73 (s, 1H),
7.50e7.54 (m, 1H), 7.57 (dd, J¼1.52, 8.48 Hz, 1H), 7.67 (d, J¼8.40 Hz,
7.79 (t, J¼8.80 Hz, 2H); 13C NMR (100 MHz, CDCl3):
d 21.3, 121.3,
2H), 8.18 (d, J¼8.48 Hz, 1H); 13C NMR (100 MHz, CDCl3):
d
110.5,
123.2, 125.3, 126.1, 127.4, 128.8, 130.1, 130.5, 131.0, 131.4, 131.9, 135.1,
136.3, 136.8, 140.7, 153.3, 165.2, 196.5; IR (cmꢁ1): 3132, 1667, 1580,
1399, 1067, 753, 725; HRMS-ESI (m/z): calcd for C21H15BrNOS
(MþH): 408.0058, found 408.0064.
120.4, 123.6, 124.8, 125.7, 128.4, 128.9, 129.2, 130.4, 130.8, 135.3,
137.7, 139.9, 141.0, 141.6, 150.5, 160.0, 194.3; IR (cmꢁ1): 3106, 1684,
1585, 1283, 1042, 741; HRMS-ESI (m/z): calcd for C20H12Cl2NO2
(MþH): 368.0245, found 368.0247.
Acknowledgements
4.2.3. 2-{[5-Methyl-2-(4-methylbenzoyl)]phenyl}benzothiazole
(3q). Yellow solid, mp 125e127 ꢀC; 1H NMR (400 MHz, CDCl3):
We are grateful to the National Natural Science Foundation of
China (Nos. 21172200, 21102134)forfinancialsupport tothis research.
d
2.28 (s, 3H), 2.50 (s, 3H), 7.08 (d, J¼7.72 Hz, 2H), 7.25e7.42 (m, 4H),
7.66 (d, J¼7.76 Hz, 2H), 7.74e7.78 (m, 2H), 7.82 (d, J¼8.12 Hz, 1H);
13C NMR (100 MHz, CDCl3):
21.2, 21.5, 121.3, 123.3, 125.0, 125.9,
d
Supplementary data
128.8, 128.9, 129.5, 130.2, 130.7, 132.0, 135.2, 135.4, 137.1, 140.2,
143.4, 153.4, 165.6, 197.3; IR (cmꢁ1): 3133, 1660, 1400, 1269, 753;
HRMS-ESI (m/z): calcd for C22H18NOS (MþH): 344.1104, found
344.1113.
Supplementary data related to this article can be found online at
http://dx.doi.org/10.1016/j.tet.2013.04.052.
References and notes
4.2.4. 2-{[2-(4-Methoxybenzoyl)-5-methyl]phenyl}benzothiazole
(3r). Light yellow solid, mp 121e124 ꢀC; 1H NMR (400 MHz,
1. (a) Surburg, H.; Panten, J. Common Fragrance and Flavor Materials, 5th ed.;
Wiley-VCH: Weinheim, Germany, 2006; (b) Romines, K. R.; Freeman, G. A.;
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Masson, P. J.; Coup, D.; Millet, J.; Brown, N. L. J. Biol. Chem. 1995, 270, 2662.
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M.; Darses, S.; Genet, J.-P. J. Am. Chem. Soc. 2004, 126, 15356; (c) Olah, G. A.
FriedeleCrafts Chemistry; Wiley: New York, NY, 1973.
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5094; (b) Daugulis, O.; Do, H.-Q.; Shabashov, D. Acc. Chem. Res. 2009, 42, 1074; (c)
Lyons, T. W.; Sanford, M. S. Chem. Rev. 2010, 110, 1147; (d) Lu, J.-M.; Tan, X.-H.;
Chen, C. J. Am. Chem. Soc. 2007, 129, 7768; (e) Li, Z.-P.; Yu, R.; Li, H.-J. Angew.
Chem., Int. Ed. 2008, 47, 7497; (f) Lewis, J. C.; Bergman, R. G.; Ellman, J. A. Acc.
Chem. Res. 2008, 41, 1013; (g) Li, Z.-G.; Capretto, D. A.; Rahaman, R.; He, C. Angew.
Chem., Int. Ed. 2007, 46, 5184; (h) Lebrasseur, N.; Larrosa, I. J. Am. Chem. Soc. 2008,
130, 2926; (i) Ackermann, L.; Vicente, R.; Kapdi, A. R. Angew. Chem., Int. Ed. 2009,
48, 9792; (j) Nakao, Y.; Kanyiva, K. S.; Hiyama, T. J. Am. Chem. Soc. 2008, 130,
2448; (k) Lewis, J. C.; Berman, A. M.; Bergman, R. G.; Ellman, J. A. J. Am. Chem. Soc.
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Saidi, O.; Iggo, J. A.; Xiao, J.-L. J. Am. Chem. Soc. 2008, 130, 10510; (q) Chan, J.;
Baucom, K. D.; Murry, J. A. J. Am. Chem. Soc. 2007, 129, 14106; (r) Ackermann, L.
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CDCl3):
d
2.51 (s, 3H), 3.76 (s, 3H), 6.78 (d, J¼8.88 Hz, 2H),
7.25e7.40 (m, 4H), 7.73e7.79 (m, 4H), 7.85 (d, J¼8.04 Hz, 1H); 13C
NMR (100 MHz, CDCl3):
d 21.2, 55.2, 113.4, 121.3, 123.3, 125.0,
125.9, 128.6, 130.2, 130.7, 130.8, 131.7, 131.9, 135.5, 137.2, 140.1,
153.4, 163.1, 165.6, 196.3; IR (cmꢁ1): 3124, 1656, 1599, 1400, 1260,
1029, 759; HRMS-ESI (m/z): calcd for C22H18NO2S (MþH):
360.1053, found 360.1061.
4.2.5. 2-[(2-Benzoyl-5-methyl)phenyl]benzothiazole (3s). Light yel-
low solid, mp 121e123 ꢀC; 1H NMR (400 MHz, CDCl3):
d 2.89 (s, 3H),
7.24e7.30 (m, 3H), 7.32e7.41 (m, 3H), 7.44e7.46 (m, 1H), 7.72e7.77
(m, 4H), 7.79 (d, J¼8.08 Hz, 1H); 13C NMR (100 MHz, CDCl3):
d 21.2,
121.2, 123.2, 125.0, 125.9, 127.9, 128.9, 129.0, 130.0, 130.7, 132.0,
132.3, 135.1, 136.8, 137.7, 140.4, 153.2, 165.4, 197.5; IR (cmꢁ1): 3130,
1665, 1602, 1399, 759; HRMS-ESI (m/z): calcd for C21H16NOS
(MþH): 330.0947, found 330.0952.
4.2.6. 2-{[2-(4-Chlorobenzoyl)-5-methyl]phenyl}benzothiazole
(3t). Light yellow solid, mp 132e135 ꢀC; 1H NMR (400 MHz,
4. (a) Whitfiekd, S. R.; Sanford, M. S. J. Am. Chem. Soc. 2007, 129, 15142; (b) Stuart,
D. R.; Villemure, E.; Fagnou, K. J. Am. Chem. Soc. 2007, 129, 12072; (c) Zhang, Y.-H.;
Feng, J.-Q.; Li, C.-J. J. Am. Chem. Soc. 2008, 130, 2900; (d) Chen, X.; Dobereiner, G.;
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F. W.; Glorius, F. J. Am. Chem. Soc. 2010, 132, 9982.
CDCl3): d 2.54 (s, 3H), 7.25 (s, 1H), 7.27e7.29 (m, 1H), 7.30e7.44 (m,
4H), 7.68e7.72 (m, 2H), 7.74 (s, 1H), 7.80 (t, J¼7.44 Hz, 2H); 13C
NMR (100 MHz, CDCl3):
d 21.2, 121.2, 123.1, 125.2, 126.0, 128.3,
128.7, 130.0, 130.3, 130.9, 131.9, 135.0, 136.3, 136.4, 138.6, 140.6,
153.2, 165.1, 196.2; IR (cmꢁ1): 3131, 1666, 1583, 1399, 1088, 754;
HRMS-ESI (m/z): calcd for C21H15ClNOS (MþH): 364.0563, found
364.0565.
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Y.-N.; Li, B.-Z.; Mao, F.; Li, X.-S.; Kwong, F. Y. Org. Lett. 2011, 13, 3258.
ꢀ
6. (a) Xiao, F.-H.; Shuai, Q.; Zhao, F.; Basle, O.; Deng, G.-J.; Li, C.-J. Org. Lett. 2011, 13,
1614; (b) Yu, Y.; Chen, D.-T.; Wang, X.-W. Adv. Synth. Catal. 2011, 353, 3373.
7. (a) Sondhi, S. M.; Singh, N.; Kumar, A.; Lozach, O.; Meijer, L. Bioorg. Med. Chem.
2006, 14, 3758; (b) Rida, S. M.; Ashour, F. A.; El-Hawash, S. A. M.; Elsemary, M. M.;
Badr, M. H.; Shalaby, M. A. Eur. J. Med. Chem. 2005, 40, 949; (c) Rodríguez, A. D.;
4.2.7. 2-{[2-(2,4-Dichlorobenzoyl)-5-methyl]phenyl}benzothiazole
(3u). light yellow solid, mp 124e126 ꢀC; 1H NMR (400 MHz,
CDCl3):
d
2.51 (s, 3H), 6.97 (dd, J¼1.76, 8.34 Hz, 1H), 7.20 (d,
ꢁ
Ramírez, C.; Rodríguez, I. I.; Gonzalez, E. Org. Lett. 1999, 1, 527.
J¼1.76 Hz, 1H), 7.25e7.28 (m, 1H), 7.31e7.36 (m, 1H), 7.40e7.45 (m,
2H), 7.58e7.61 (m, 2H), 7.79 (d, J¼8.00 Hz, 1H), 7.97 (d, J¼8.16 Hz,
8. (a) Yang, F.; Wu, Y.-J.; Zhu, Z.-W.; Zhang, J.-L.; Li, Y.-N. Tetrahedron 2008, 64,
6782; (b) Yang, F.; Wu, Y.-J.; Li, Y.-N.; Wang, B.; Zhang, J.-L. Tetrahedron 2009, 65,
914; (c) Leng, Y.-T.; Yang, F.; Zhu, W.-G.; Wu, Y.-J.; Li, X. Org. Biomol. Chem. 2011, 9,
5288; (d) Leng, Y.-T.; Yang, F.; Zhu, W.-G.; Zou, D.-P.; Wu, Y.-J.; Cai, R.-R. Tetra-
hedron 2011, 67, 6191; (e) Zhang, Q.; Li, C.; Yang, F.; Li, J.-Y.; Wu, Y.-J. Tetrahedron
2013, 69, 320.
1H); 13C NMR (100 MHz, CDCl3):
d 21.4, 121.3, 123.5, 125.3, 126.2,
128.4, 130.3, 130.4,130.5,131.1,131.5,132.8,133.8,135.3,136.1,136.5,
136.9, 141.9, 153.2, 165.3, 194.4; IR (cmꢁ1): 3133, 1681, 1580, 1400,