Palladium-catalyzed formation of phenolic compounds by reaction of carbonyl compounds with carbon dioxide

Article abstract of DOI:10.1039/c2cc37194d

The use of carbon dioxide as a renewable and environmentally friendly source of carbon is highly attractive. A novel and efficient protocol for the synthesis of phenolic compounds from carbonyl compounds and carbon dioxide in the presence of a catalytic amount of Pd(OAc)₂ has been developed. This reaction is appealing for industries and is a tool for the sequestration of carbon dioxide.

Full text of DOI:10.1039/c2cc37194d

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COMMUNICATION
Palladium-catalyzed formation of phenolic compounds by reaction of
carbonyl compounds with carbon dioxidew
Qi Gao,a Xian-chun Tan,a Ying-ming Pan,*a Heng-shan Wanga and Ying Liang*b
Received 2nd October 2012, Accepted 23rd October 2012
DOI: 10.1039/c2cc37194d
The use of carbon dioxide as a renewable and environmentally
friendly source of carbon is highly attractive. A novel and
efficient protocol for the synthesis of phenolic compounds from
carbonyl compounds and carbon dioxide in the presence of a
catalytic amount of Pd(OAc)2 has been developed. This reaction
is appealing for industries and is a tool for the sequestration of
carbon dioxide.
Table 1 Optimization of reaction conditionsa
Entry
Catalyst
Base
Solvent
Yieldb [%]
1
2
PdCl2
K2CO3
K2CO3
K2CO3
K2CO3
Na2CO3
K3PO4
NaOH
Et3N
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMAC
MFM
DMB
DMSO
CH3COCH3
CH3CN
83
85
91
Carbon dioxide (CO2), as the main culprit in global warming,
is an inexhaustible source of carbon on earth. If CO2 can be
captured and used in industrial production, it can not only
reduce the worsening greenhouse effect, but also resolve the
energy crisis. Therefore, the investigation of efficient catalytic
processes for CO2 transformation into useful chemical feedstock
is a highly attractive field.1 In the past decade, lots of chemical
reactions utilizing CO2 as raw material have been reported,2
which have aroused our considerable interest in CO2. Herein,
we present our independent finding that palladium-catalyzed
reaction of carbonyl compounds proceeded smoothly with CO2
to give the corresponding phenolic compounds in good yields,
which are well known for their anti-allergenic, anti-atherogenic,
anti-inflammatory, anti-microbial, antioxidant, anti-thrombotic,
cardioprotective and vasodilatory effects.3
Pd(dba)2
Pd(OAc)2
—
3
4c
5
Trace
44
56
None
None
None
None
78
69
81
82
None
None
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(OAc)2
Pd(OAc)2
6
7
8
9
(i-Pr)2NH
—
10d
11
12
13
14
15
16
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
a
Reaction conditions: 1a (0.6 mmol), air (1 atm), [Pd] (5 mol%), base
b
(0.5 equiv.), solvent (1 mL), 100 1C, 2 h. Isolated yield of the pure
product based on 1a. In the absence of catalyst. In the absence of base.
c
d
Initially, the reaction conditions were optimized starting
from ethyl acetoacetate (1a) and air (1 atm) in the presence of
K2CO3 in DMF at 100 1C with various palladium catalysts, as
summarized in Table 1. It was observed that Pd(OAc)2 gave
the best result (Table 1, entry 3). Then, in order to prove that
the CO2 comes from the air, a series of control experiments
have been done (for details, see the ESIw). PdCl2 and Pd(dba)2
were also effective, albeit affording the products with slightly
diminished yields (Table 1, entries 1 and 2). In the absence of a
palladium source, only a trace amount of the desired product
was observed under the same reaction conditions (Table 1,
entry 4). Base also plays an important role in the catalyst
systems. When K2CO3 was replaced by Na2CO3 or K3PO4, a
moderate yield was achieved. Other bases like NaOH, Et3N, and
(i-Pr)2NH were found to be ineffective (Table 1, entries 7–9). A
control experiment confirmed that in the absence of K2CO3 the
reaction led to recovery of materials (Table 1, entry 10). Further
inspection of the reaction conditions revealed that this reaction
also proceeded efficiently in solvents such as DMAC (dimethyl-
acetamide), MFM (N-methylformamide), DMB (N,N-dimethyl-
benzamide), and DMSO (dimethyl sulfoxide) (Table 1, entries
11–14), whereas CH3COCH3 and CH3CN were found to be
unfavorable (Table 1, entries 15 and 16). On the basis of the
above experiments, the optimized reaction conditions are
summarized as follows: Pd(OAc)2, K2CO3, and DMF.
a Key Laboratory for the Chemistry and Molecular Engineering of
Medicinal Resources (Ministry of Education of China),
School of Chemistry & Chemical Engineering of Guangxi Normal
University, Guilin 541004, People’s Republic of China.
E-mail: panym2004@yahoo.com.cn; Fax: +86-773-5803930;
Tel: +86-773-5846279
b School of Life and Environmental Sciences, Guilin University of
Electronic Technology, Guilin, 541004, People’s Republic of China.
E-mail: liangyi0774@yahoo.com.cn
w Electronic supplementary information (ESI) available: Experimental
section and NMR data for the prepared compounds. CCDC 904546.
For ESI and crystallographic data in CIF or other electronic format
see DOI: 10.1039/c2cc37194d
With the optimized reaction conditions in hands, we started
to investigate the scope and limitation of this reaction, and the
results are summarized in Table 2. Methyl, ethyl,4 isopropyl,
c
12080 Chem. Commun., 2012, 48, 12080–12081
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Table 2 Synthesis of phenolic compounds 2 catalyzed by Pd(OAc)2/
K2CO3
and ethyl 3-oxohexanoate could also participate in the reac-
tion and give the desirable results (Table 2, 7b–9b). It was
particularly noteworthy that 4-toluenesulfonylacetone was
also suitable for this reaction (Table 2, 10b). Gratifying,
acetylacetone and benzoylacetone could be readily introduced
in the reaction, providing the corresponding phenolic com-
pounds 11b and 12b, but the yields were lower. However, 1,3-
diphenylpropane-1,3-dione and diethyl malonate failed to afford
the desired products and led to recovery of starting materials.
In summary, we have identified a novel protocol for the
synthesis of phenolic compounds by reaction of carbonyl
compounds with carbon dioxide. This method has the unique
advantages of employing CO2 as a carbon source and simple
carbonyl compounds as substrates. Thus, this method constitutes
an economical and environmentally benign process for the
synthesis of phenolic compounds. Further studies to broaden
the substrate scope of the process are underway in our laboratory.
We thank the project 973 (2011CB512005), the National Natural
Science Foundation of China (41206077 and 81260472), Guangxi
Natural Science Foundation of China (2012GXNSFAA053027,
2011GXNSFD018010 and 2010GXNSFF013001) for financial
support.
a
Notes and references
1 For selected recent reviews on the use of CO2 in organic synthesis,
see: (a) K. Inamoto, N. Asano, K. Kobayashi, M. Yonemoto and
Y. Kondo, Org. Biomol. Chem., 2012, 10, 1514; (b) Y. Zhang and
S. N. Riduan, Angew. Chem., Int. Ed., 2011, 50, 6210; (c) A. Behr
and G. Henze, Green Chem., 2011, 13, 25; (d) I. I. F. Boogaerts and
S. P. Nolan, Chem. Commun., 2011, 47, 3021; (e) S. N. Riduan and
Y. Zhang, Dalton Trans., 2010, 39, 3347.
2 For recent representative examples, see: (a) D. Yu, M. X. Tan and
Y. Zhang, Adv. Synth. Catal., 2012, 354, 969; (b) C. J. Whiteoak,
E. Martin, M. M. Belmonte, J. Benet-Buchholz and A. W. Kleij,
Adv. Synth. Catal., 2012, 354, 469; (c) C. D. N. Gomes, O. Jacquet,
a
Reaction conditions: 1 (0.6 mmol), air (1 atm), Pd(OAc)2 (5 mol%),
K2CO3 (0.5 equiv.), DMF (1 mL), 100 1C.
C. Villiers, P. Thuery, M. Ephritikhine and T. Cantat, Angew.
´
Chem., Int. Ed., 2012, 51, 187; (d) S. Li, W. Yuan and S. Ma,
Angew. Chem., Int. Ed., 2011, 50, 2578; (e) L. Ackermann, Angew.
Chem., Int. Ed., 2011, 50, 3842; (f) A. Polyzos, M. O. Brien,
T. P. Petersen, I. R. Baxendale and S. V. Ley, Angew. Chem., Int.
Ed., 2011, 50, 1190; (g) X. Zhang, W. Z. Zhang, X. Ren, L. L. Zhang
and X. B. Lu, Org. Lett., 2011, 13, 2402; (h) I. I. F. Boogaerts,
G. C. Fortman, M. R. L. Furst, C. S. J. Cazin and S. P. Nolan,
Angew. Chem., Int. Ed., 2010, 49, 8674; (i) W. Z. Zhang, W. J. Li,
X. Zhang, H. Zhou and X. B. Lu, Org. Lett., 2010, 12, 4748;
(j) L. Zhang, J. Cheng, T. Ohishi and Z. Hou, Angew. Chem., Int.
Ed., 2010, 49, 8670; (k) L. Gu and Y. Zhang, J. Am. Chem. Soc.,
2010, 132, 914; (l) Y. Kayaki, M. Yamamoto and T. Ikariya, Angew.
Chem., Int. Ed., 2009, 48, 4194; (m) J. Takaya and N. Iwasawa,
J. Am. Chem. Soc., 2008, 130, 15254; (n) T. Matsuo and
H. Kawaguchi, J. Am. Chem. Soc., 2006, 128, 12362; (o) K. Ukai,
M. Aoki, J. Takaya and N. Iwasawa, J. Am. Chem. Soc., 2006,
128, 8706.
3 (a) B. G. Wang, W. W. Zhang and X. J. Duan, Food Chem., 2009,
113, 1101; (b) N. Balasundram, K. Sundram and S. Samman, Food
Chem., 2006, 99, 191; (c) J. Shi, H. Nawaz and J. Pohorly, Food Rev.
Int., 2005, 21, 139.
4 The yield of the large-scale synthesis of diethyl 4-hydroxy-6-methyl-
isophthalate 1b from ethyl acetoacetate (1a) (60 mmol, 7.8 g) was
87%.
Fig. 1 X-ray crystal structure of 2b. The thermal ellipsoids are at the
50% probability level.
isobutyl, tert-butyl, and n-pentyl acetoacetates all reacted
smoothly affording the target products in good to excellent
yields (Table 2, 1b–6b). The crystallization of compound 2b
from ethanol gave single crystals suitable for X-ray analysis. Fig. 1
illustrates the molecular structure of phenolic compound 2b.
In addition, methyl 3-oxopentanoate, ethyl 3-oxopentanoate,
c
This journal is The Royal Society of Chemistry 2012
Chem. Commun., 2012, 48, 12080–12081 12081