Copper-catalyzed oxidative cyclization of arylamides and ?2-diketones: New synthesis of 2,4,5-trisubstituted oxazoles

Article abstract of DOI:10.1039/c4ra14394a

A novel copper catalyzed approach to oxazoles via enamide intermediates was developed from benzamides and ?2-diketones. The successive condensation and cyclization reactions afforded various 2,4,5-trisubstituted oxazoles in good yields.

Full text of DOI:10.1039/c4ra14394a

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ARTICDLOI:E10.10T39/YC4RPA143E94A
Copper-Catalyzed Oxidative Cyclization of Arylamides and β-Diketones:
New Synthesis of 2,4,5-Trisubstituted Oxazoles
Yang Bai, a Wen Chen, a Ya Chen, a Huawen Huang, a Fuhong Xiaoa and Guo-Jun Deng a*
Received (in XXX, XXX) Xth XXXXXXXXX 20XX, Accepted Xth XXXXXXXXX 20XX
5
DOI: 10.1039/b000000x
functionalization. However, some highly functionalized enamide
45 precursors require several steps to prepare. Therefore, the in situ
formation of enamides from readily available starting materials
such as β-diketones is highly desirable for one pot construction of
oxazoles. There are only few reports on multi-substituted oxazole
synthesis from β-diketones and arylamides or benzyl amines.14
50 Moreover, a leaving group need to be introduced into the α-
position of β-diketones. Efficient method to prepare multi-
substituted oxazoles in one pot from β-diketones without leaving
substituents is highly desirable. Herein, we report an efficient
copper-catalyzed oxidative cyclization strategy from readily
55 available benzamides and β-diketones (via enamide intermediate),
providing the 2,4,5-trisubstituted oxazoles in good yields
(Scheme 1, c).15 In the whole process, the acyl functional group is
retained and located selectively at the ortho position of the
oxygen atom.16
A novel copper catalyzed approach to oxazoles via enamide
intermediates was developed from benzamides and β-
diketones. The successive condensation and cyclization
reactions afforded various 2,4,5-trisubstituted oxazoles in
10 good yields.
Substituted oxazoles are an important class of heterocycles that
are ubiquitous in biologically active molecules, including natural
products, agrochemicals and pharmaceutical drugs.1 A large
number of oxazole-containing natural products have been isolated
15 from marine invertebrates and microorganisms.2 Moreover, many
synthetic trisubstituted oxazoles have been evaluated to show
activity against diabetes, breast cancer and pancreatic cancer.3
(Figure 1) Consequently, great effort has been paid on the
development of efficient synthetic methods to access substituted
20 oxazoles, and most of the existed methods are using ketone
derivatives as the starting materials.4 Traditionally, a range of
highly substituted and complex oxazoles are prepared via
cyclodehydration of α-acylaminoketones, esters, or amides (the
Robison-Gabriel oxazole synthesis,).5 Nevertheless, this method
25 requires the use of highly functionalized diketone substrates
(Scheme 1, a). Additionally, catalytic decomposition of α-
diazocarbonyl compounds in nitriles,6 photolysis and pyrolysis of
N-acylisoozalones7 can provide alternative procedures for the
preparation of functionalized oxazole derivatives. Transition
30 metals such as copper,8 rhodium,9 ruthenium10 and gold11 are
successfully used as the cyclization catalysts to afford various
substituted oxzoles.
60
(a) Robinson-Gabriel Condensation
R
O
O
O
R
R2
Bronsted or Lewis acids
- H2O
R1
N
H
R2
N
R1
(b) Cyclization of Enamides
O
R
X
R
R2
transition metal-catalysts
- HX or "H2"
R2
O
N
R1
N
H
R1
X = I, Br, SR, H
(c) This Work
O
R1
R1
R2
O
N
CuBr
K2S2O8
OMe
OMe
O
R2
R1
O
O
H
O
O
O
+
NH
O
+
NH2
Ar
O
N
AcOH
O
N
N
R2
Ar
Ar
H
O
O
O
Me
N
O
H
O
O
H
MeO
OMe
Anti-diabetic agent
O
R2
O
R1
via
or
Pimprinine
Annuloline
Ar
N
H
R1
Ar
N
H
R2
35 Figure 1. Selected oxazole-containing drugs
Scheme 1. Various procedures for multi-substituted oxazole
In recent years, enamides bearing β-vinylic C-heteroatom
bonds are proved to be versatile cyclization precursors to
construct the oxazole ring (Scheme 1, b).12 The groups of
40 Buchwald and Stahl reported copper-mediated oxidative
cyclization of enamides to 2,5-disubstituted oxazoles via vinylic
C-H functionalization.13 This method provided a more direct
approach to substituted oxzoles by avoiding the substrate
synthesis
65
In the first experiment we examined the reaction between
benzamide (1a) and pentane-2,4-dione (2a) in toluene using
molecular oxygen as the oxidant. As shown in Table 1, four
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Page 2 of 4
different copper salts were screened using p-toluenesulfonic acid
(TsOH) as the acidic additive. Among the catalysts investigated,
CuBr showed the best efficiency (entries 1-4). Various oxidants 35 the desired product 3h was observed in only 38% yield (entry 8).
substituent significantly decreased the reaction yield. For
example, when 4-nitrobenzamide (1h) was used in the reaction,
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DOI: 10.1039/C4RA14394A
were investigated instead of oxygen using CuBr as the catalyst
(entries 5-8). Among the various oxidants screened, K2S2O8
showed the best activity and its use improved the reaction yield to
24% (entry 7). The choice of acidic additive is very important,
Similar yield was observed when the methyl substituent shifted
from para to meta position (entries 2 and 9).
5
Table 2. Reaction of pentane-2,4-dione (2a) with various
and the product 3a could be obtained in 46% yield when acetic 40 aromatic amidesa
acid was used (entry 10). Slightly higher yield was obtained when
O
O
CuBr
10 the reaction was carried out in Cl2CHCHCl2 (entry 14). The
reaction yield increased from 51% to 64% when the ratio of
1a:2a changed to 2:1 (entry 15). The desired product could be
obtained in 82% yield when the reaction temperature increased
O
O
R1
O
N
K2S2O8
NH2
R1
+
AcOH
Cl2CHCHCl2
o
o
from 120 C to 140 C (entry 16). Compared with CuBr2, CuBr
15 showed better efficiency (entry 16 and 17).
1
2a
3
Yield [%]b
Entry
Arylamides
O
Product
Table 1. Optimization of the reaction conditionsa
NH2
O
O
R1
R1 = H
1 = CH3
catalyst
oxidant
O
O
O
NH2
+
1
1a
1b
1c
3a
83
additive
N
R
3b
3c
3d
2
3
81
82
84
3a
1a
2a
R1 = OCH3
Yield [%]b
R1 = tert-butyl
Entry Catalyst
Oxidant
Additive
Solvent
4
5
6
7
8
1d
1e
1f
Cu(OAc)2
1
R
1 = F
3e
3f
75
70
68
38
O2
TsOH
TsOH
TsOH
TsOH
TsOH
TsOH
TsOH
toluene
toluene
toluene
toluene
toluene
toluene
toluene
toluene
toluene
toluene
toluene
DMF
8
7
R1 = Cl
CuSO4
2
O2
R1 = Br
R1 = NO2
1g
1h
3g
3h
CuBr2
3
O2
11
12
trace
5
CuBr
4
O2
O
CuBr
5
DDQ
TBHP
K2S2O8
NH2
CuBr
6
3i
9
1i
80
CuBr
7
24
7
a
Conditions: 1 (0.4 mmol), 2a (0.2 mmol), CuBr (20 mol%),
K2S2O8 (0.4 mmol), AcOH (0.4 mmol), Cl2CHCHCl2 (0.4 mL),
CuBr
8
Dess-Martin TsOH
CuBr
9
K2S2O8
K2S2O8
K2S2O8
K2S2O8
K2S2O8
K2S2O8
K2S2O8
CF3COOH
11
46
32
10
44
140 oC, 36 h under Argon. b Isolated yield based on 2a.
CuBr
10
CH3COOH
PivOH
The scope of the reaction with β-diketones is outlined in Table
45 3. 1,3-Diphenylpropane-1,3-dione (2b) reacted with benzamide to
give (2,4-diphenyloxazol-5-yl)(phenyl)methanone (3j) in 81%
yield (entry 1). Besides symmetrical β-diketones, various
unsymmetrical β-diketones were also employed in the oxidative
cyclization reaction, providing the corresponding products in
50 moderate to good yields (entries 2-9). For regioselectivity of the
unsymmetrical β-diketones, the steric hindrance is a key factor. In
all cases, 5-acyl substituted oxazoles were the major products.
When 1-(naphthalen-1-yl)butane-1,3-dione (2h) was used, the 5-
acyl substituted oxazole 3p was obtained almost as the sole
55 product (entry 7). Furthermore, extension of this reaction to
heteroaryl β-diketones proved to be successful (entry 8). It is
important to point out that changing the substituting position on
the aromatic ring of 1-phenylbutane-1,3-dione (2c) greatly
influenced the reaction yields of the corresponding products
60 (entries 6 and 9). Unfortunately, no desired product was observed
when β-diketone was replaced by ethyl acetoacetate.
CuBr
11
CuBr
12
CH3COOH
CH3COOH
CH3COOH
CH3COOH
CuBr
13
1,4-dioxane
CuBr
14
Cl2CHCHCl2
Cl2CHCHCl2
51
64
15c
CuBr
16c,d
CuBr
Cl2CHCHCl2
Cl2CHCHCl2
82
70
K2S2O8
K2S2O8
CH3COOH
CH3COOH
c,d CuBr2
17
a
Conditions: 1a (0.2 mmol), 2a (0.3 mmol), catalyst (20 mol%),
oxidant (2.0 equiv.), additive (2.0 equiv.), solvent (0.4 mL), 120
20 oC, 36 h under argon (under oxygen for entries 1-4). b GC yield
based on 1a. c 1a (0.4 mmol), 2a (0.2 mmol), yield based on 2a.
d At 140 oC.
The scope of this reaction was studied under the optimized
25 conditions (Table 2). Arylamides with electron-donating group at
the para position smoothly coupled with pentane-2,4-dione (2a)
to give the heterocyclic products in high yields (entries 1-4).
When halogen substituents presented at the para position of
amides, the corresponding products were obtained in fairly good
30 yields (entries 5-7). For example, 68% yield of 3g which could be
converted to other useful compounds easily was obtained when
an active bromo substituent existed. Strong electron-withdrawing
A series of control experiments were designed to investigate
the reaction mechanism (Scheme 2). When the reaction of 1a
with 2a was stopped after 2 h, 4a and 3a were obtained in 8% and
65 9% yields, respectively (Scheme 2, a). The starting materials
could be smoothly converted into the desired product 3a with
2
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extension of time whereas no significant change was observed for
intermediate 4a (Scheme 2, b). The isolated 4a could be further
intermediate B. Subsequent oxidation of the intermediate B by
25 Cu(II) provides the product 3a and releases Cu(I) which can be
View Article Online
re-oxidized to participate the next catalytic cycle.
Table 3. Reactions of 1a with various β-diketonesa
DOI: 10.1039/C4RA14394A
[O]
R2
O
O
N
CuBr
O
R2
R3
R3
R2
O
O
O
O
Cu(I)
Cu(II)
SET
K2S2O8
H
H+
H
+
O
O
O
O
AcOH, 140 oC
+
Ph
NH2
+
1a
2a
- H2O
R3
N
Ph
N
H
Ph
Ph
Ph
N
H
1a
2
4a
3
3'
A
Yield [%]b
Entry
1c
Ketone
Product
[O]
H+
2
: R = R3 = Ph
3j
2b
81
82
O
O
Cu(II)
Cu(I)
2c: R2 = Ph, R3 = CH3
3k:3k' (3:1)
3l:3l' (4:1)
2
SET
O
O
H
Ph
3
4
5
2d: R2 = 4-Me-C6H5, R3 = CH3
81
76
66
Ph
N
N
H+
: R2 = 4-MeO-C6H5, R3 = CH3
2e
3m:3m'(4:1)
3n:3n' (3:1)
B
3a
2f: R2 = 4-F-C6H5, R3 =CH3
Scheme 3. Proposed mechanism
30
2
: R = 4-Cl-C6H5, R3 = CH3
73
6
2g
3o:3o' (4:1)
2h: R2 = 1-naphthyl, R3 = CH3
2i: R2 = 2-thienyl, R3 = CH3
2j: R2 = 2-Cl-C6H5, R3 = CH3
3p:3p' (80:1)
3q:3q' (8:1)
3r: 3r' (4:1)
Conclusions
7
8
9
75
77
50
In conclusion, we have developed a novel approach for the
synthesis of oxazoles using CuBr as the catalyst. Readily
available β-diketones and primary arylamides were used as the
35 starting materials. 5-Acyl substituted oxazoles were obtained as
the sole products in all cases. Halogen substituted benzamides
also could be employed for this kind of transformation. This
strategy affords an efficient approach for the synthesis of
biologically active oxazoles with acyl substituents from readily
40 available starting materials with cheap and low toxic copper
catalyst. The generality and synthetic applications of this
methodology are under investigation.
a
5
Conditions: 1a (0.4 mmol), 2 (0.2 mmol), CuBr (20 mol%),
K2S2O8 (2.0 equiv.), AcOH (2.0 equiv.), Cl2CHCHCl2 (0.4 mL),
140 oC, 36 h under Argon. b Isolated yield based on 2. c 48 h.
Standard
conditions
O
O
1a
1a
2a
3a
+
+
(a)
(b)
+
Ph
N
2 h
H
4a
9%
, 8%
Acknowledgements
Standard
conditions
This work was supported by the National Natural Science
45 Foundation of China (21172185, 21372187), the Hunan
2a
3a
4a
9%
+
8 h
32%
Provincial
Innovative
Foundation
for
Postgraduate
Standard
(CX2014B258), the New Century Excellent Talents in University
from Ministry of Education of China (NCET-11-0974) and the
Research Fund for the Doctoral Program of Higher Education of
50 China, Ministry of Education of China (20124301110005).
conditions
4a
1a
3a
(c)
(d)
8 h
80%
Standard
conditions
2a
3a
4a
trace
+
+
Notes and references
TEMPO
(2 equiv)
trace
aKey Laboratory of Environmentally Friendly Chemistry and Application
of Ministry of Education, College of Chemistry, Xiangtan University,
Xiangtan 411105, China; Fax: (+86)-731-58292251; e-mail:
55 gjdeng@xtu.edu.cn;
10
Scheme 2. Control experiments
† Electronic Supplementary Information (ESI) available: [details of any
supplementary information available should be included here]. See
DOI: 10.1039/b000000x/
transformed into 3a in 80% yield under the standard reaction
conditions (Scheme 2, c). These results suggested that enamide
might be the key intermediate during the formation of oxazoles.
15 Only trace amounts of 3a and 4a were observed when two equiv
of TEMPO was added to the reaction mixture (Scheme 2, d). This
means that a radical process was possibly involved in this
transformation. Based on these competition experiments and
related literatures,13 a possible mechanism to illustrate this
20 reaction is presented in Scheme 3. Condensation of 1a with 2a
yields an enamide intermediate 4a which can be further converted
into a radical cation A in the presence of Cu(II) and Cu(I) is
released and oxidized into Cu(II). The cyclization of A generates
60
1
(a) D. C. Palmer and E. C. Taylor, The Chemistry of Heterocyclic
Compounds. Oxazoles: Synthesis, Reactions, and Spectroscopy, Parts
A & B, Wiley, New Jersey, 2004, vol. 60; (b) I. J. Turchi, Ind. Eng.
Chem. Prod. Res. Dev. 1981, 20, 32; (c) I. J. Turchi and M. J. S.
Dewar, Chem. Rev. 1975, 75, 389; (d) J. Zhang and M. A. Ciufolini,
Org. Lett. 2011, 13, 390; (e) B. Wang, T. M. Hansen, L. Weyer, D.
Wu, T. Wang, M. Christmann, Y. Lu, L. Ying, M. M. Engler, R. D.
Cink, C. S. Lee, F. Ahmed and C. J. Forsyth, J. Am. Chem. Soc. 2011,
133, 1506.
65
This journal is © The Royal Society of Chemistry [year]
Journal Name, [year], [vol], 00–00 | 3

RSC Advances
Page 4 of 4
13 (a) C. W. Cheung and S. L. Buchwald, J. Org. Chem. 2012, 77, 7526;
2
(a) N. Lindquist, W. Fenical, G. D. Van Duyne and J. Clardy, J. Am.
Chem. Soc. 1991, 113, 2303; (b) Z. Cruz-Monserrate, H. C.Vervoort,
R. L. Bai, D. Newman, S. B. Howell, G. Los, J. T. Mullaney, M. D.
Williams, G. R. Pettit, W. Fenical and E. Hamel, Mol. Pharmacol.
2003, 63, 1273; (c) J. Kobayashi, M. Tsuda, H. Fuse, T. Sasaki and Y.
Mikami, J. Nat. Prod. 1997, 60, 150. For selected examples on
natural products synthesis containing 2,4-disubsituted oxazole moiety,
see: (d) J. Li, S. Jeong, L. Esser and P. G. Harran, Angew. Chem. Int.
Ed. 2001, 40, 4765; (e) K. C. Nicolaou, D. Y. K. Chen, X. Huan, T.
Ling, M. Bella and S. A. Snyder, J. Am. Chem. Soc. 2004, 126,
12888; (f) J. R. Davis, P. D. Kane and C. J. Moody, J. Org. Chem.
2005, 70, 7305.
(a) Y. Momose, T. Maekawa, T. Yamano, M. Kawada, H. Odaka, H.
Ikeda and T. Sohda, J. Med. Chem. 2002, 45, 1518; (b) W. S. Yang,
K. Shimada, D. Delva, M. Patel, E. Ode, R. Skouta and B. R.
Stockwell, ACS Med. Chem. Lett. 2012, 3, 35; c) A. Y.Shaw, M. C.
Henderson, G. Flynn, B. Samulitis, H. Han, S. P. Stratton, H. H. S.
Chow, L. H. Hurley and R. T. Dorr, J. Pharmacol. Exp. Ther. 2009,
331, 636.
(b) A. E. Wendlandt and S.S. Stahl, Org. Biomol. Chem. 2012, 10,
70
3866; (c) R. Martin, A. Cuenca and S. L. Buchwald, Org. Lett. 2007,
View Article Online
9, 5521. (d) C. Zhang, C. H. Tang and N. Jiao. Chem. Soc. Rev. 2012,
DOI: 10.1039/C4RA14394A
41, 3464.
5
14 (a) C. F. Wan, J. T. Zhang, S. J. Wang, J. M. Fan and Z. Y. Wang,
Org. Lett. 2010, 12, 2338; (b) J. C. Lee, H. J. Choi and Y. C. Lee,
Tetrahedron Lett. 2003, 44, 123.
75
15 The reactions in ref. 14a mainly provided ester substituted oxazoles
and there is only one example for acetyl substituted oxazole
synthesis. The position of the acetyl group in ref. 14a is ortho to the
nitrogen atom which is different with ours.
10
15
3
80 16
During the preparation of this manuscript, Jiang and co-workers
reported a similar method for oxazole preparation from amides and
ketones using PdCl2/CuBr2 as catalysts and NaHCO3 as the base: M.
F. Zheng, L. B. Huang, H. W. Huang, X. W. Li, W. Q. Wu, H. F.
Jiang, Org. Lett. 2014, 16, 5906.
85
20 4
For the classical synthetic methods to oxazoles, see: (a) I. J. Turchi
and M. J. S. Dewar, Chem. Rev. 1975, 75, 389. For the recent
examples of synthetic methods to oxazoles, see: (b) B. Shi, A. J.
Blake, W. Lewis, I. B. Campbell, B. D. Judkins and C. J. Moody, J.
Org. Chem. 2010, 75, 152; (c) W. He, C. Li, L. Zhang, J. Am. Chem.
Soc. 2011, 133, 8482; (d) I. Cano, E. Álvarez, M. C. Nicasio and P. J.
Pérez, J. Am. Chem. Soc. 2011, 133, 191; (e) J. Xie, H. Jiang, Y.
Cheng and C. Zhu, Chem. Commun. 2012, 48, 979; (f) W. J. Xue, Q.
Li, Y. P. Zhu, J. G. Wang and A. X. Wu, Chem. Commun. 2012, 48,
3485; (g) J. P. Weyrauch, A. S. K. Hashmi, A. Schuster, T. Hengst,
S. Schetter, A. Littmann, M. Rudolph, M. Hamzic, J. Visus, F.
Rominger, W. Frey and J. W. Bats, Chem. Eur. J. 2010, 16, 956; (h)
Z. Li, L. Ma, J. Xu, L. Kong, X. Wu and H. Yao, Chem. Commun.
2012, 48, 3763; (i) X. Liu, R. Cheng, F. F. Zhao, D. Zhang-Negrerie,
Y. F. Du and K. Zhao, Org. Lett. 2012, 14, 5480; (j) A. Herrera, R.
Martínez-Alvarez, P. Ramiro, D. Molero and J. Almy, J. Org. Chem.
2006, 71, 3026.
25
30
35
5
(a) R. Robinson, J. Chem. Soc. 1909, 95, 2167; (b) S. Gabriel, Chem.
Ber. 1910, 43, 1283. For selected recent examples, see: (c) E. Biron,
J. Chatterjee and H. Kessler, Org. Lett. 2006, 8, 2417; (d) J. F. Sanz-
Cervera, R. Blasco, J. Piera, M. Cynamon, I. Ibáñez, M. Murguía
and S. Fustero, J. Org. Chem. 2009, 74, 8988; (e) M. J. Thompson,
H. Adams and B. Chen, J. Org. Chem. 2009, 74, 3856.
40
6
M. P. Doyle, W. E. Buhro, J. G. Davidson, R. C. Elliot, J. W.
Hoekstra and M. Oppenhuizen, J. Org. Chem. 1980, 45, 3657.
45 7 R. H. Prager, J. A. Smith, B. Weber aand C. M. Williams, J. Chem.
Soc., Perkin Trans. 1 1997, 2665.
8
9
R. Martín, A. Cuenca and S. L. Buchwald, Org. Lett. 2007, 9, 5521.
A. S. K. Hashmi, J. P. Weyrauch, W. Frey and J. W. Bats, Org. Lett.
2004, 6, 4391.
50 10 M. D. Milton, Y. Inada, Y. Nishibayashi and S. Uemura, Chem.
Commun. 2004, 2712.
11 (a) B. Clapham, C. Spanka and K. D. Janda, Org. Lett. 2001, 3, 2173;
(b) Y. R. Lee, S. H. Yeon, Y. Seo and B. S. Kim, Synthesis 2004,
2787.
55 12 For the cyclization of enamides bearing β-vinylic carbonheteroatom
bonds, see the following: (i) C−Br bond: (a) C. Shin, Y. Sato, H.
Sugiyama, K. Nanjo and J. Yoshimura, Bull. Chem. Soc. Jpn. 1977,
50, 1788; (b) J. Das, J. A. Reid, D. R. Kronenthal, J. Singh, P. D.
Pansegrau and R. H. Mueller, Tetrahedron Lett. 1992, 33, 7835; (c)
60
S. K. Chattopadhyay, J. Kempson, A. McNeil, G. Pattenden, M.
Reader, D. E. Rippon and D. Waite, J. Chem. Soc. Perkin Trans. 1
2000, 2415; (d) K. Schuh and F. Glorius, Synthesis. 2007, 15, 2297;
(ii) C−I bond: (e) P. M. T. Ferreira, L. S. Monteiro and G. Pereira,
Eur. J. Org. Chem. 2008, 4676; (f) P. M. T. Ferreira, E. M. S.
Castanheira, L. S. Monteiro, G. Pereira and H. Vilaça, Tetrahedron
2010, 66, 8672; (iii) C−S bond: (g) N. C. Misra and H. Ila, J. Org.
Chem. 2010, 75, 5195.
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