Ligand-free palladium-catalyzed aerobic oxidative coupling of carboxylic anhydrides with arylboronic acids

Article abstract of DOI:10.1002/asia.201402314

We report a new, effective and environmentally friendly protocol for selective aerobic oxidative coupling of arylboronic acids with carboxylic anhydrides in the presence of ligand-free palladium catalyst. The aryl benzoates are obtained in good to excellent yields.

Full text of DOI:10.1002/asia.201402314

COMMUNICATION
DOI: 10.1002/asia.201402314
Ligand-Free Palladium-Catalyzed Aerobic Oxidative Coupling of Carboxylic
Anhydrides with Arylboronic Acids
Weiyan Yin,*[a] Haifeng He,[b] Yani Zhang,[a] and Tong Long[a]
Abstract: We report a new, effective and environmentally
friendly protocol for selective aerobic oxidative coupling of
arylboronic acids with carboxylic anhydrides in the presence
of ligand-free palladium catalyst. The aryl benzoates are ob-
tained in good to excellent yields.
Many researchers have reported the conversion of arylbor-
onic acids into esters in the presence of catalysts. For in-
stance, Cheng and co-workers reported an aromatic esterifi-
cation reaction of aldehydes and arylboronic acids with
5 mol% palladium N-heterocyclic carbene (NHC) complex
under air;[8] Gois and co-workers showed an efficient iron/
NHC-catalyzed aerobic oxidative aromatic esterification of
aldehydes with boronic acids;[9] the groups of Anand[10] and
Zhang[11] reported the NHC-catalyzed aerobic oxidative aro-
matic esterification of aldehydes with boronic acids; Wuꢀs
group has reported palladium-catalyzed aerobic oxidative
coupling of acyl chlorides with boronic acids using molecu-
lar oxygen;[12] Cheng et al.[13] and Liu et al.[14] reported the
Molecular oxygen is an environmentally friendly oxidant.
The use of molecular oxygen as both oxidant and reactant
in the presence of a catalytic metal has exceptional advan-
tages for applications in organic synthesis,[1] especially in
transition metal-catalyzed aerobic oxidative coupling reac-
tion.[2]
Benzoate derivatives have been found in numerous bio-
logically active compounds, ranging from natural products
to pharmaceuticals. They also serve as important building
blocks in material industries.[3] A common route for prepar-
ing these compounds involves esterification reactions, trans-
esterification reactions,[4] and Baeyer–Villiger oxidation re-
actions.[5] Another method for the preparation of benzoate
derivatives utilizes organocatalytic esterification[6] and tran-
sition-metal catalyzed coupling reactions.[7] Although indi-
vidually having some synthetic advantages, most traditional
methods suffer from some experimental drawbacks, such as
harsh reaction conditions, low yield, lack of functional group
compatibility and the need to use toxic or unstable reagents.
During the past few years, much attention has been fo-
cused on the use of organoboron reagents as environmental-
ly benign reactants to synthesize benzoate derivatives. This
fact is attributed to the intriguing properties of organoboron
reagents, such as high stability, nontoxicity, and easy han-
dling. In view of these distinct advantages, the use of orga-
noboron reagents has become very common in the field.[8–14]
CuACHTNGUTRENNU(G OTf)2-mediated Chan–Lam reaction of carboxylic acids
with arylboronic acids to access phenolic esters. Although
these transformations are efficient, ligands were used and
relatively high loadings of the transition-metal catalysts
were required.
Carboxylic anhydrides are very important reagents fre-
quently used as the preferred reactive intermediates for
preparation of esters.[15] Hence, it is an interesting attempt
to synthesize benzoate derivatives using carboxylic anhy-
drides under mild conditions. Great progress has been made
in the past decades in palladium-catalyzed coupling reac-
tions of carboxylic anhydrides with arylboronic acids for
ketone preparation.[16] However, to our knowledge, no re-
sults regarding the palladium-catalyzed aerobic oxidative
coupling of carboxylic anhydrides with arylboronic acids
using molecular oxygen have been reported. As part of our
continuing interest in the development of new reactions
using O2 as the terminal oxidant,[17] we report herein a selec-
tive palladium-catalyzed aerobic oxidative coupling route
for the preparation of aryl benzoates using carboxylic anhy-
drides and arylboronic acids as the starting materials. The
reaction is conducted under ligand-free conditions
(Scheme 1).
[a] Dr. W. Yin, Y. Zhang, T. Long
National Biopesticide Engineering Research Center
Hubei Academy of Agricultural Science
Wuhan, 430064 (P. R. China)
The palladium-catalyzed aerobic oxidative coupling of
benzoic anhydride 1a with phenylboronic acid 2a using KF
Fax : (+86)27-59101911
E-mail: hpywy2006@163.com
[b] Dr. H. He
Key Laboratory of Pesticide & Chemical Biology
Ministry of Education, College of Chemistry
Central China Normal University
Wuhan 430079, Hubei (P. R. China)
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/asia.201402314.
Scheme 1. Pd-catalyzed oxidative coupling reaction.
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Table 1. Screening of the reaction conditions.[a]
of the desired product 3aa. On the other hand, NEt3 as an
organic base had little effect on the reaction (Table 1,
entry 10). Higher reaction temperatures favored the reaction
(Table 1, entries 1 and 18). It is noteworthy that a high yield
was still isolated after 10 h when 0.5 mmol of 1a was treated
with 1.2 mmol of 2a and 5.0 equiv of KF in MeCN at room
temperature (Table 1, entry 18).
Entry
Pd source
PdCl2
Solvent
Base
Yield [%][b]
3aa
4aa
As listed in Table 2, the aerobic oxidative coupling reac-
tions of phenylboronic acid 2a with various carboxylic anhy-
drides were carried out in the presence of PdCl2 and KF. Ini-
tially, a variety of substituted carboxylic anhydrides 1b–m
were investigated for the reaction with 2a (Table 2, en-
tries 1–12). Most of the substrates with a variety of substitu-
ents afforded the products in good to excellent yields under
the optimum reaction conditions. The reaction was equally
facile with both electron-donating and electron-withdrawing
substituents present on the aromatic carboxylic anhydrides,
resulting in excellent yields of the coupling products. For ex-
ample, aromatic carboxylic anhydrides 1b–j, with methyl,
methoxy, chloro, fluoro, bromo, and nitro groups, respective-
ly, on the aryl moiety, reacted with 2a, PdCl2, and KF
smoothly in good yields (Table 2, entries 1–9). para- and
meta-substituted aromatic carboxylic anhydrides gave corre-
sponding products in good to excellent yields. Diverse re-
sults were obtained for ortho-substituted aromatic carboxyl-
ic anhydrides. o-Nitrobenzoic anhydride 1i produced the
corresponding product 3ia in a lower yield of 48% (Table 2,
entry 8). Gratifyingly, both 3-phenylpropionic anhydride 1l
and thiophene-2-carboxylic anhydride 1m were successful
for the aerobic oxidative coupling reaction with 2a, afford-
ing the corresponding products 3la and 3ma in 73% and
89% yields, respectively (Table 2, entries 11 and 12). How-
ever, an attempt at the aerobic oxidative coupling reaction
of acetic anhydride with 2a failed.
Next, the scope of the esterification reactions of benzoic
anhydride 1a with several arylboronic acids was explored
under the standard conditions (Table 3). Functional groups,
including methyl, trifluoromethyl, fluoro, chloro, bromo,
nitro, and methoxy groups were perfectly tolerated as sub-
stituents on the phenyl ring moiety of arylboronic acids
(Table 3, entries 1–9). In the presence of PdCl2 and KF, 3ae
was isolated in 95% yield after 5 h by the coupling of elec-
tron-rich arylboronic acid 2e bearing a methoxy group with
1a (Table 3, entry 4). However, the efficiency of the PdCl2/
KF system decreased for the coupling reaction of electron-
withdrawing arylboronic acids. For example, the coupling of
1a with arylboronic acids 2i and 2j afforded 75% and 83%
yields of the corresponding products 3ai and 3aj, respective-
ly (Table 3, entries 8 and 9). The coupling of 1a with ortho-
substituted arylboronic acids such as 2h also resulted in
a slight decrease of yield (Table 3, entry 7). Unfortunately,
the reaction of 1a with 2-thienylboronic acid was unsuccess-
ful under the standard conditions.
1
2
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
dioxane
CH2Cl2
THF
KF
KF
KF
KF
Na2CO3
Cs2CO3
CsF
K2CO3
K3PO4
Et3N
KF
KF
KF
KF
KF
KF
KF
KF
93
75
80
33
82
86
90
85
83
0
0
12
10
Pd
Pd
U
3[c]
4
A
U
53
5
6
7
8
PdCl2
PdCl2
PdCl2
PdCl2
PdCl2
PdCl2
PdCl2
PdCl2
PdCl2
PdCl2
PdCl2
PdCl2
–
trace
0
0
trace
trace
0
9
10
11
12
13
14[d]
15[e]
16[f]
17[g]
18[h]
45
26
37
3
95
93
0
50
61
52
toluene
MeCN
MeCN
MeCN
MeCN
trace
0
0
0
0
PdCl2
84
[a] Unless otherwise indicated, the reaction conditions were: 1a
(0.5 mmol), 2a (1.2 mmol), Pd source (1 mol%), base (5.0 equiv), and an-
hydrous solvent (3 mL) for 5 h at 608C under O2. [b] Yield of isolated
product. [c] PdACHTUNGTRENNUNG(OAc)2 (1 mol%) at 608C under O2 for 12 h. [d] For 24 h.
[e] PdCl2 (5 mol%). [f] PdCl2 (10 mol%). [g] Without palladium.
[h] PdCl2 (1 mol%) at room temperature for 10 h.
as the base and dry MeCN as the solvent was first examined,
and the results are summarized in Table 1. PdCl2, Pd
and [PdCl2A(PPh3)2] all catalyzed the aerobic oxidative cou-
ACHTUNGERTN(NUNG OAc)2,
CHTUNGTRENNUNG
pling reaction. PdCl2 turned out to be the best catalyst in
terms of yields and reaction rates (Table 1, entries 1–4). In
the presence of 1 mol% PdCl2, treatment of 0.5 mmol 1a
with 1.2 mmol 2a and 5.0 equiv KF afforded a 93% yield of
the corresponding coupled product 3aa in 5 h (Table 1,
entry 1), while low yields of 3aa were isolated after 5–12 h
using PdACHTUNGTRENNUNG(OAc)2 and [PdCl2AHCTUNGTRNE(NUGN PPh3)2] as the catalysts (Table 1,
entries 2–4). The influence of the amount of PdCl2 on the
catalytic reactions was also investigated (Table 1, entries 1
and 15–18). A PdCl2 loading of 1 mol% gave the best oxida-
tive coupling product yield (Table 1, entry 1). The oxidative
coupling reaction did not occur in the absence of a palladium
catalyst (Table 1, entry 17). Next, the solvents of dioxane,
CH2Cl2, THF, and toluene were investigated (Table 1, en-
tries 11–14). In toluene, treatment of substrate 1a with 2a,
PdCl2 (1 mol%), and KF (5.0 equiv) at 608C after 24 h af-
forded only 3% yield of the corresponding coupled product
3aa (Table 1, entry 14), whereas the yield of 3aa was en-
hanced sharply to 93% in 5 h when MeCN was used as the
solvent (Table 1, entry 1). Subsequently, the reaction was in-
vestigated in the presence of different bases (Table 1, en-
tries 1 and 5–10). Interestingly, some inorganic bases, such
as Na2CO3, Cs2CO3, CsF, K2CO3, K3PO4, and KF promoted
the coupling reaction and gave good yields (Table 1, en-
tries 1 and 5–9). KF showed the best result with 93% yield
To understand the mechanism, some control experiments
were carried (Scheme 2). Firstly, no desired product was ob-
tained when the reaction between benzoic acid and phenyl-
boronic acid 2a was investigated under the optimal reaction
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Weiyan Yin et al.
Table 2. Oxidative esterification of different carboxylic anhydrides with
phenylboronic acid.[a]
Table 3. Oxidative esterification of different arylboronic acids with ben-
zoic anhydride[a]
Entry
1
Benzoate
Yield [%][b]
89
Entry
1
Benzoate
Yield [%][b]
85
2
3
4
87
86
96
2
3
87
80
4
5
6
7
8
95
93
91
82
75
5
6
88
85
7
8
80
48
9
83
9
66
10
11
86
92
10
11
71
73
[a] Unless otherwise indicated, the reaction conditions were: 1a
(0.5 mmol), 2 (1.0 mmol), PdCl2 (1 mol%), KF (5.0 equiv), and MeCN
(3 mL) for 5 h at 608C under O2. [b] Yield of isolated product.
12
89
[a] Unless otherwise indicated, the reaction conditions were:
(0.5 mmol), 2a (1.0 mmol), PdCl2 (1 mol%), KF (5.0 equiv), and
MeCN (3 mL) for 5 h at 608C under O2. [b] Yield of isolated product.
1
of benzoic acid with phenylboronic acid or phenol. Next, to
confirm the participation of dioxygen in this transformation,
the reaction between benzoic anhydride 1a and phenylbor-
onic acid 2a under an 18O2 atmosphere was performed. We
found that the reaction proceeded smoothly to give the de-
sired product [18O]-3aa containing 18O in 82% yield
(Scheme 2c). The 18O-atom-containing product [18O]-3aa
was determined by LC-MS analysis. However, the reaction
conditions (Scheme 2a). Subsequently, phenol was not ob-
served from phenylboronic acid 2a under the standard reac-
tion conditions (Scheme 2b). These findings demonstrate
that the reaction does not proceed through the esterification
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Weiyan Yin et al.
Experimental Section
In the typical procedure, carboxylic anhydride (0.5 mmol), arylboronic
acid (1.0 mmol), PdCl2 (1 mol%) and KF (2.5 mmol) were dissolved in
3 mL of dry MeCN in an oven-dried Schlenk tube. An O2 balloon was at-
tached, and the Schlenk tube was purged 3 times, then the resulting mix-
ture was heated to 608C and stirred for 5 h. The reaction mixture was
then cooled to room temperature and extracted with ethyl acetate (3ꢂ
10 mL), washed with a saturated aqueous solution of NaCl, dried over
Na2SO4, filtered and evaporated under reduced pressure. The residue
was purified by silica gel column chromatography to afford the desired
product.
Scheme 2. Control experiments of the Pd-catalyzed aerobic oxidative
coupling reaction.
Acknowledgements
This work was supported by the National Natural Science Foundation of
China (NO. 31101472).
Keywords: anhydrides
· cross-coupling · homogeneous
catalysis · oxidation · palladium
[1] a) S. F. J. Hackett, R. M. Brydson, M. H. Gass, I. Harvey, A. D.
Newman, K. Wilson, A. F. Lee, Angew. Chem. Int. Ed. 2007, 46,
8593–8596; Angew. Chem. 2007, 119, 8747–8750; b) F.-Z. Su, Y.-M.
Liu, L.-C. Wang, Y. Cao, H.-Y. He, K.-N. Fan, Angew. Chem. Int.
Ed. 2008, 47, 334–337; Angew. Chem. 2008, 120, 340–343; c) H.
Wang, S.-X. Deng, Z.-R. Shen, J.-G. Wang, D.-T. Ding, T.-H. Chen,
Green Chem. 2009, 11, 1499–1502; d) H. Yang, X. Han, Z. Ma, R.
Wang, J. Liu, X. Ji, Green Chem. 2010, 12, 441–451; e) R. A. Peria-
na, O. Mironov, D. Taube, G. Bhalla, C. J. Jones, Science 2003, 301,
814–818; f) S. S. Stahl, Science 2005, 309, 1824–1826; g) C. Zhang,
N. Jiao, Angew. Chem. Int. Ed. 2010, 49, 6174–6177; Angew. Chem.
2010, 122, 6310–6313; h) Z. Shi, B. Zhang, Y. Cui, N. Jiao, Angew.
Chem. Int. Ed. 2010, 49, 4036–4041; Angew. Chem. 2010, 122, 4130–
4135; i) C. Zhang, N. Jiao, J. Am. Chem. Soc. 2010, 132, 28–29.
[2] a) C. Zhang, Z. Xu, L. Zhang, N. Jiao, Angew. Chem. Int. Ed. 2011,
50, 11088–11092; Angew. Chem. 2011, 123, 11284–11288; b) A.
Wang, H. Jiang, J. Am. Chem. Soc. 2008, 130, 5030–5031; c) Y. Liu,
F. Song, S. Guo, J. Am. Chem. Soc. 2006, 128, 11332–11333.
[3] a) U. Beginn, G. Zipp, M. Moller, Chem. Eur. J. 2000, 6, 2016–2023;
b) M. C. Berndt, M. R. Bowles, G. J. King, B. Zerner, Biochim. Bio-
phys. Acta. 1996, 1298, 159–166; c) M. D. Barratt, D. A. Basketter,
D. W. Roberts, Toxicol. in Vitro 1994, 8, 823–826; d) C. James, V.
Snieckus, J. Org. Chem. 2009, 74, 4080–4093.
Scheme 3. A possible mechanism for the present reaction.
of benzoic anhydride 1a with phenylboronic acid 2a under
a N2 atmosphere was unsuccessful. Therefore, it is concluded
that oxygen is essential for the transformation of carboxylic
anhydrides to esters.
Thus, a working mechanism for the present reaction is
proposed as outlined in Scheme 3 on the basis of the report-
ed mechanisms and the present results.[12,18–21] The reaction
is proposed to initiate from the oxidation of Pd0 species by
O2 to generate a Pd(O2)[12,18–21] intermediate A.[12,18–20] Subse-
quently, transmetalation of A with ArB(OH)2 2 gives the
trans-[ArPd(OH)Cl2][21] intermediate B, which reacts with
carboxylic anhydrides 1 to afford an intermediate C. Finally,
C undergoes reductive elimination to give the desired aryl
benzoates 3 and regenerate the active Pd0 species.
[4] a) M. H. Sarvari, H. Sharghi, Tetrahedron 2005, 61, 10903–10907;
b) F. Tamaddon, M. A. Amrollahi, L. Sharafat, Tetrahedron Lett.
2005, 46, 7841–7844; c) S. T. A. Shah, K. M. Khan, H. Hussain,
M. U. Anwar, M. Fecker, W. Voelter, Tetrahedron 2005, 61, 6652–
6656; d) Y. Oohashi, K. Fukumoto, T. Mukaiyama, Bull. Chem. Soc.
Jpn. 2005, 78, 1508–1519.
In summary, we have developed a new, effective and envi-
ronmentally friendly protocol for palladium-catalyzed aero-
bic oxidative coupling to selectively prepare aryl benzoates.
In the presence of PdCl2 and KF, arylboronic acids smoothly
underwent the reaction with carboxylic anhydrides in good
to excellent yields. Compared with the reported palladium-
catalyzed aerobic oxidative coupling,[8,12] the present reac-
tion can be conducted under ligand-free conditions with rel-
atively low loading of PdCl2.
[5] J. S. Yadav, B. V. S. Reddy, A. K. Basak, A. V. Narsaiah, Chem. Lett.
2004, 33, 248–249.
[6] K. Ishihara, S. Nakagawa, A. Sakakura, J. Am. Chem. Soc. 2005,
127, 4168–4169.
[7] a) D. A. Watson, X. Fan, S. L. Buchwald, J. Org. Chem. 2008, 73,
7096–7101; b) X.-F. Wu, H. Neumann, M. Beller, ChemCatChem
2010, 2, 509–513; c) C. Liu, J. Wang, L. Meng, Y. Deng, Y. Li, A.
Lei, Angew. Chem. Int. Ed. 2011, 50, 5144–5148; Angew. Chem.
2011, 123, 5250–5254.
[8] C. Qin, H. Wu, J. Chen, M. Liu, J. Cheng, W. Su, J. Ding, Org. Lett.
2008, 10, 1537–1540.
[9] J. N. Rosa, R. S. Reddy, N. R. Candeias, P. M. S. D. Cal, P. M. P.
Gois, Org. Lett. 2010, 12, 2686–2689.
&
&
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ꢁ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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www.chemasianj.org
Weiyan Yin et al.
[10] P. Arde, B. T. Ramanjaneyulu, V. Reddy, A. Saxena, R. V. Anand,
Org. Biomol. Chem. 2012, 10, 848–851.
[11] J.-J. Meng, M. Gao, Y.-P. Wei, W.-Q. Zhang, Chem. Asian J. 2012, 7,
872–875.
[12] J. Chen, Y. Peng, M. Liu, J. Ding, W. Su, H. Wu, Adv. Synth. Catal.
2012, 354, 2117–2122.
[13] L. Zhang, G. Zhang, M. Zhang, J. Cheng, J. Org. Chem. 2010, 75,
7472–7474.
[14] J.-J. Dai, J.-H. Liu, D.-F. Luo, L. Liu, Chem. Commun. 2011, 47,
677–679.
[15] a) P. Gupta, S. Paul, Green Chem. 2011, 13, 2365–2372; b) I. Mo-
hammadpoor-Baltork, H. Aliyan, A. R. Khosropour, Tetrahedron
2001, 57, 5851–5854.
[16] a) X.-F. Lin, Y. Li, S.-Y. Li, Z.-K. Xiao, J.-M. Lu, Tetrahedron 2012,
68, 5806–5809; b) A. Yu, L. Shen, X. Cui, D. Peng, Y. Wu, Tetrahe-
dron 2012, 68, 2283–2288; c) L. J. Gossen, K. Ghosh, Angew. Chem.
Int. Ed. 2001, 40, 3458–4360; Angew. Chem. 2001, 113, 3566–3568.
[17] W. Yin, C. He, M. Chen, H. Zhang, A. Lei, Org. Lett. 2009, 11, 709–
712.
[18] For a review on palladium peroxo complexes as intermediates in
catalytic reactions, see: S. S. Stahl, Angew. Chem. Int. Ed. 2004, 43,
3400–3420; Angew. Chem. 2004, 116, 3480–3501.
[19] a) S. S. Stahl, J. L. Thorman, R. C. Nelson, M. A. Kozee, J. Am.
Chem. Soc. 2001, 123, 7188–7189; b) B. V. Popp, S. S. Stahl, J. Am.
Chem. Soc. 2007, 129, 4410–4422; c) A. N. Campbell, P. B. White,
I. A. Guzei, S. S. Stahl, J. Am. Chem. Soc. 2010, 132, 15116–15119;
d) B. V. Popp, C. M. Morales, C. R. Landis, S. S. Stahl, Inorg. Chem.
2010, 49, 8200–8207; e) B. A. Steinhoff, S. R. Fix, S. S. Stahl, J. Am.
Chem. Soc. 2002, 124, 766–767.
[20] a) D. R. Jensen, M. J. Schultz, J. A. Mueller, M. S. Sigman, Angew.
Chem. Int. Ed. 2003, 42, 3810–3813; Angew. Chem. 2003, 115, 3940–
3943; b) J. T. Bagdanoff, B. M. Stoltz, Angew. Chem. Int. Ed. 2004,
43, 353–357; Angew. Chem. 2004, 116, 357–361; c) M. Yamashita,
K. Goto, T. Kawashima, J. Am. Chem. Soc. 2005, 127, 7294–7295;
d) K. S. Yoo, C. H. Yoon, K. W. Jung, J. Am. Chem. Soc. 2006, 128,
16384–16393; e) Q. Liu, G. Li, J. He, J. Liu, P. Li, A. Lei, Angew.
Chem. Int. Ed. 2010, 49, 3371–3374; Angew. Chem. 2010, 122, 3443–
3446.
[21] a) trans-[ArPd(OH)L2] species have been mentioned, see: C.
Adamo, C. Amatore, I. Ciofini, A. Jutand, H. Lakmini, J. Am.
Chem. Soc. 2006, 128, 6829–6836, and references therein; b) see ref.
[12].
Received: March 31, 2014
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COMMUNICATION
Oxidative Coupling
Weiyan Yin,* Haifeng He, Yani Zhang,
Tong Long
&&&& — &&&&
Ligand-Free Palladium-Catalyzed
Aerobic Oxidative Coupling of
Carboxylic Anhydrides with Arylbor-
onic Acids
O2 can do: A ligand-free, palladium-
catalyzed aerobic oxidative coupling
between carboxylic anhydrides and
arylboronic acids has been developed
to selectively prepare aryl benzoates.
The reaction proceeds with a PdCl2
loading of 1 mol% under mild condi-
tions.
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