Copper-catalyzed decarboxylative methylation of aromatic carboxylic acids with PhI(OAc)2

Article abstract of DOI:10.1002/ejoc.201301815

The copper-catalyzed decarboxylative methylation of aromatic carboxylic acids was developed by using PhI(OAc)₂ to provide a new strategy for the methylation of aryl acids through the decarboxylation of alkyl acids. The mechanism and the roles of each reactant in the reaction were investigated extensively. Copyright

Full text of DOI:10.1002/ejoc.201301815

Job/Unit: O31815
/KAP1
Date: 20-02-14 11:08:49
Pages: 6
SHORT COMMUNICATION
DOI: 10.1002/ejoc.201301815
Copper-Catalyzed Decarboxylative Methylation of Aromatic Carboxylic Acids
with PhI(OAc)2
Yuyu Jiang,[a] Shulei Pan,[a] Yanghui Zhang,*[a,b] Jingxun Yu,[a] and Hongqiang Liu[a]
Keywords: Synthetic methods / Decarboxylation / Methylation / Carboxylic acids / Copper / Radicals
The copper-catalyzed decarboxylative methylation of aro-
matic carboxylic acids was developed by using PhI(OAc)2 to
provide a new strategy for the methylation of aryl acids
through the decarboxylation of alkyl acids. The mechanism
and the roles of each reactant in the reaction were investi-
gated extensively.
volve esterification with acids and alcohols or transesterifi-
cation with esters and alcohols.[8] As these two reactions
are equilibrium reactions, an excess amount of one of the
reagents has to be used or the water or alcohol product
must be removed to force the reaction forward to the side
of the product. The addition of dehydration reagents is an
alternative efficient method, but this increases the complex-
ity of the reaction system and produces a large amount of
byproducts.[9] Owing to the importance of esters and the
existing drawbacks of the current reactions, esterification is
still the subject of extensive study, and a variety of new
reactions have been disclosed,[10] which include a few novel
transition-metal-catalyzed esterification reactions.[11] With
the great advantages of carboxylic acids taken into con-
sideration, decarboxylative esterification should be a novel
intriguing reaction for the preparation of esters. However,
this reaction is expected to be a challenge, because one of
the carboxylic acids must undergo decarboxylation selec-
tively. As mentioned previously, aliphatic carboxylic acids
generally decarboxylate through a mechanism different to
that of aromatic carboxylic acids, and this would provide
the opportunity to achieve selective decarboxylation of
either the aryl acids or the alkyl acids (Figure 1). On the
basis of this reasoning, we envisioned that aryl acids could
be esterified by decarboxylation of alkyl acids, which can
decarboxylate through a radical mechanism to produce
alkyl radicals. It is noted that esterification products arising
from decarboxylation of aliphatic carboxylic acids, primar-
Introduction
Over the past few years, the decarboxylative transforma-
tion of carboxylic acids has gained extensive attention, and
a rapidly growing number of reactions of this type have
been reported.[1] As chemical reactants, carboxylic acids
have many desirable properties and great advantages, which
include low cost, nontoxicity, relatively high stability, and
ready availability. Furthermore, as CO2 is the sole by-
product from carboxylic acids, decarboxylation reactions
may reduce the formation of chemical wastes.[2] Most of the
recently reported decarboxylative transformations involve
transition-metal-catalyzed decarboxylative cross-coupling
reactions of aromatic carboxylic acids. In transition-metal-
catalyzed reactions, carboxylic acids may serve as synthetic
equivalents of (pseudo)halides or organometallic rea-
gents,[1c] and they undergo a variety of cross-coupling reac-
tions.[3] In this context, most of the reactions involve car-
bon–carbon bond formation, and carbon–heteroatom
forming reactions are quite rare.[4] However, decarbox-
ylative reactions of aliphatic carboxylic acids have also at-
tracted considerable interest, and quite a few novel reac-
tions have been discovered.[5] Mechanistically, the decar-
boxylation of aromatic acids often involves the formation
of organometallic species enabled by transition metals,[6]
whereas aliphatic carboxylic acids decarboxylate through
radical mechanisms or under oxidative conditions.[1a]
As one of the most common functional groups, the ester
functionality is ubiquitous in organic molecules.[7] Conven-
tional methods for the preparation of esters primarily in-
[a] Department of Chemistry, Tongji University,
1239 Siping Road, Shanghai 200092, P. R. China
E-mail: zhangyanghui@tongji.edu.cn
http://chemweb.tongji.edu.cn/En/Faculty/Details/1520a611-
7212-4e28-94b8-1233420c9053
[b] Key Laboratory of Yangtze River Water Environment, Ministry
of Education,
Siping Road 1239, P. R. China
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.201301815.
Figure 1. A new strategy for the synthesis of esters through the
decarboxylation of carboxylic acids.
Eur. J. Org. Chem. 0000, 0–0
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
1

Job/Unit: O31815
/KAP1
Date: 20-02-14 11:08:49
Pages: 6
Y. Jiang, S. Pan, Y. Zhang, J. Yu, H. Liu
SHORT COMMUNICATION
ily as lead tetracarboxylates, has been observed.[12] In these methylation products were observed in the absence of
reactions, the esters were generally formed as coproducts, Cu(OAc)2 or PhI(OAc)2.
and the alkyl and carboxylate moieties are from the same
Having identified the optimal protocol for the methyl-
alkyl acid. One exception is the allylation reaction of acids ation of 2-nitrobenzoci acid, we probed the substrate scope
with lead tetraallylate.[13] Herein, we describe a novel decar- with regard to the aromatic carboxylic acids. The protocol
boxylative methylation of aromatic carboxylic acids.
proved to be compatible with a broad range of benzoic
acids and tolerated a wide variety of functional groups. As
summarized in Table 2, both meta- and para-nitrobenzoic
acids underwent the methylation reaction effectively, albeit
in a lower yield. A range of electron-withdrawing groups
were well tolerated, including nitrile, trifluoromethyl,
Results and Discussion
The research was initiated by the observation that methyl
2-nitrobenzoate was formed in 32% yield if 2-nitrobenzoic
acid was treated with PhI(OAc)2 and a catalytic amount of
Cu(OAc)2 in DMF (Table 1). Solvent screening revealed
that the reaction gave a similar result with CH3CN as the
solvent and also that the methylation product was not pro-
duced in THF. Gratifyingly, the addition of acetic anhy-
dride (1 equiv.) improved the yield to 88%. The yield almost
remained unaffected if 0.5 equiv. acetic anhydride was used,
but it decreased substantially in the case of 0.2 equiv. acetic
anhydride. The yield was further improved to 94% by using
a DMF/CH3CN mixture as the solvent. With a satisfactory
yield in hand, we investigated the effects of the reaction
conditions on the yield. Therefore, the use of 0.15 equiv.
Cu(OAc)2 afforded a similar yield, but the yield decreased
to 86% with the use of 0.1 equiv. catalyst. The use of
1 equiv. PhI(OAc)2 resulted in a huge decrease in the yield,
and lowering the temperature or shortening the reaction
time also decreased the yield substantially. Furthermore, no
Table 2. Substrate scope of the methylation of aromatic carboxylic
acids.[a]
Table 1. Survey of the reaction conditions.
[a] Determined by analysis of the crude product by 1H NMR spec-
troscopy by using CHCl2CHCl2 as an internal standard. [b] Yield
of the isolated product. [c] PhI(OAc)2 (1 equiv.). [d] 110 °C.
[e] 10 min. [f] No Cu(OAc)2. [g] No PhI(OAc)2.
[a] Yield of the isolated product. [b] Determined by 1H NMR spec-
troscopy.
2
www.eurjoc.org
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 0000, 0–0

Job/Unit: O31815
/KAP1
Date: 20-02-14 11:08:49
Pages: 6
Decarboxylative Methylation of Aromatic Carboxylic Acids
ketone, and ester. Substrates with fluoride, chloride, and the yield of the reaction in the absence of any hydrides.
iodide at the ortho, meta, and para positions were methyl- Furthermore, the addition of acetic acid (1 equiv.) resulted
ated under the reaction conditions. The methylation of in an even lower yield. On the basis of these observations
benzoic acid and its analogues with methoxy groups gave and the previous report on the role of anhydrides in the
lower yields, and disubstituted benzoic acids were also com- decomposition of PhI(OAc)2, acetic anhydride may pro-
patible. No significant amount of the methylation product mote the methylation reaction by acetylating any diacetate
for octanoic acid was observed.
that may be hydrolyzed by trace amounts of water.[14]
Generally, electron-poor benzoic acids were methylated
in higher yields than the electron-rich ones. To further study
the relative reactivities of different benzoic acids, we per-
formed the reactions by using equal amounts of benzoic
acid and a substituted benzoic acid. As shown in Figure 2,
the experiments revealed that benzoic acid was methylated
far less effectively than benzoic acids with electron-with-
drawing groups (NO2 and CN) and slightly more efficiently
than benzoic acids with electron-donating groups (OAc and
OMe).
Figure 4. Investigation into the role of acetic anhydride. Condi-
tions: Cu(OAc)2 (15 mol-%), DMF/CH3CN (0.3:0.5 mL), 130 °C,
1 h.
Next, the radical inhibitor 2,2,6,6-tetramethylpiperidine-
N-oxyl (TEMPO) was added into the reaction to investigate
if a radical was involved in this methylation reaction. As
shown in Figure 5, no methylated products were observed
in the presence of TEMPO (2 equiv.), and more import-
antly, 24% O-methylated TEMPO was formed. This pro-
vided strong evidence that a radical mechanism was opera-
tive in this methylation reaction. Notably, a similar amount
of O-methylated TEMPO was yielded even in the absence
of Cu(OAc)2, which implies that Cu(OAc)2 was not in-
volved in the formation of the methyl radical. Actually, aryl
iodine diacetate has been reported to undergo thermal de-
composition spontaneously to generate alkyl radicals via
acetoxy radical intermediates [Figure 6, Eq. (1)].[15] It is
noteworthy that the decomposition of aryl iodine diacetate
might be an ion-pair process [Figure 6, Eq. (2)]. In this pro-
cess, aryl acetate and MeI are produced.[14] The methylation
product in this report could result from the reaction be-
Figure 2. Comparison of the reactivities of benzoic acid and substi-
tuted benzoic acids. Conditions: Cu(OAc)2 (15 mol-%), Ac2O
(0.5 equiv.), DMF/CH3CN (0.3:0.5 mL), 130 °C, 1 h.
Mechanistic experiments were conducted to gain insight
into the mechanism of the methylation reaction. First, to
investigate the source of the methyl group, we performed
the methylation reaction by using PhI(OCOCD3)2 and
Cu(OTf)2 (Tf = trifluoromethylsulfonyl) in lieu of PhI-
(OAc)2 and Cu(OAc)2 respectively. As shown in Figure 3,
in the absence of acetic anhydride, [D3]methyl 2-nitrobenzo-
ate was almost the sole product. Both methylated and [D3]-
methylated products were formed in the presence of acetic
anhydride. These results demonstrated that the sources of
the methyl group were PhI(OAc)2 and acetic anhydride, and
PhI(OAc)2 should be the initial source. To obtain some
more information about the role of acetic anhydride, we
performed several comparison experiments (Figure 4).
Therefore, acetic anhydride was replaced with propionic an-
hydride. The yield decreased to 40%, which was close to
Figure 5. Investigation into the generation of methyl radicals. Con-
ditions: Ac2O (0.5 equiv.), DMF/CH3CN (0.3:0.5 mL), 130 °C, 1 h.
Figure 3. Investigation into the source of the methyl group. Condi-
tions: Cu(OTf)2 (15 mol-%), DMF/CH3CN (0.3:0.5 mL), 130 °C, Figure 6. Possible pathways for the decarboxylation of PhI-
1 h.
(OAc)2.[14]
Eur. J. Org. Chem. 0000, 0–0
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
3

Job/Unit: O31815
/KAP1
Date: 20-02-14 11:08:49
Pages: 6
Y. Jiang, S. Pan, Y. Zhang, J. Yu, H. Liu
SHORT COMMUNICATION
tween aryl acids and MeI. However, phenyl acetate was not
observed, and almost 100% PhI was recovered, which was
against a methyl iodide mechanism.
As the methylation products were not formed in the ab-
sence of a copper catalyst and Cu(OAc)2 was not involved
in the formation of the radical, the copper catalyst should
be responsible for the methylation step. Noteworthy, it has
been reported that CuII can oxidize alkyl radicals to alkyl
esters with carboxylic acids. Therefore, we propose a radical
mechanism for the methylation of aryl acids, as shown in
Scheme 1. PhI(OAc)2 decomposes to yield acetoxy radicals,
which undergo decarboxylation to afford methyl radicals.
The resulting methyl radicals are oxidized by CuII or CuIII
to form methylated aryl acids and generate CuI species,
which is oxidized, very likely by PhI(OAc)2, to CuII or CuIII
to continue the catalytic cycle.
Figure 7. Attempts at the ethylation/tert-butylation of aryl acids.
Conditions: Cu(OAc)2 (15 mol-%), Ac2O (0.5 equiv.), DMF/
CH3CN (0.3:0.5 mL), 130 °C, 1 h.
that produces alkyl radicals, which provides an opportunity
for the development of the decarboxylative alkylation of
aromatic carboxylic acids. By taking advantage of this op-
portunity, we developed the Cu-catalyzed methylation of
aromatic carboxylic acids with PhI(OAc)2. The mechanism
and the roles of each reagent in the reaction were investi-
gated. This reaction demonstrated that aromatic carboxylic
acids may be alkylated through the decarboxylation of alkyl
acids, which would provide an advantageous method for the
synthesis of esters. More detailed mechanistic studies and
the exploration of other decarboxylative alkylation reac-
tions in addition to the methylation reaction, especially for
reactions in which simple alkyl acids are used, are underway
in our laboratory.
Scheme 1. Proposed mechanism for the decarboxylative methyl-
ation of aryl acids.
As with carbocations, the stability of radicals increases
with additional alkyl substitution. In the decarboxylation
of lead tetraacetate, the relative ease of decarboxylation of
carboxylic acids is related to the stability of the carbon radi-
cals resulting from the loss of carbon dioxide: tertiaryϾ
secondaryϾ primary.[12a] Recently, the Liu and Zhu groups
independently reported the decarboxylative alkylation of
alkenes with aryl iodine diacetate.[16] In these radical-in-
volved reactions, the reactivity of the carboxylic acids also
paralleled the stability of the carbon radicals. As such, after
establishing that a radical mechanism was operating in this
methylation reaction, we envisioned that this protocol
would be applicable to the alkylation of aryl acids with
other alkylation reagents. Therefore, ethylation and tert-
butylation reactions were conducted with PhI(OCOEt)2
and PhI(OCOtBu)2. Unexpectedly, almost no desired prod-
ucts were observed no matter what anhydrides were used,
that is, acetic anhydride or propionic/tert-butanoic an-
hydride (Figure 7). In the reactions with the use of acetic
anhydride, methylation products were generated in low
Experimental Section
General Procedure for the Methylation of Aromatic Carboxylic Ac-
ids: A 50 mL sealed tube (with a Teflon high-pressure valve)
equipped with a magnetic stir bar was charged with Cu(OAc)2
(13.6 mg, 0.075 mmol) followed by carboxylic acid (0.5 mmol),
Ac2O (23.3 μL, 0.25 mmol), PhI(OAc)2 (322 mg, 1 mmol), DMF
(0.3 mL), and MeCN (0.5 mL). After the reaction mixture was
stirred at 130 °C for 1 h, it was cooled to ambient temperature. The
reaction mixture was diluted with ethyl acetate and water and then
filtered through a small pad of Celite. The filtrate was washed with
saturated aqueous NaHCO3 (5 mL) and brine (5 mL, 2ϫ). The or-
ganic phase was dried (Na2SO4) and concentrated in vacuo. The
residue was purified by silica gel preparative TLC to give the corre-
sponding product.
Supporting Information (see footnote on the first page of this arti-
cle): Experimental procedures, characterization data of synthesized
compounds, and copies of the H NMR and 13C NMR spectra.
1
Acknowledgments
yields. The mechanism responsible for this outcome remains The work was supported by the National Natural Science Founda-
tion of China (NSFC) (grant number 21372176), Tongji University
985 Phase III Funds, Pujiang Project of Shanghai Science and
Technology Commission (grant number 11PJ1409800), and the
Program for Professor of Special Appointment (Eastern Scholar)
at Shanghai Institutions of Higher Learning.
to be explored.
Conclusions
In summary, aliphatic and aromatic carboxylic acids may
decarboxylate through different mechanisms. The decar-
boxylation of alkyl acids generally involves a radical process
[1] a) N. Rodríguez, L. J. Gooßen, Chem. Soc. Rev. 2011, 40, 5030–
5048; b) R. Shang, L. Liu, Sci. China Chem. 2011, 54, 1670–
4
www.eurjoc.org
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 0000, 0–0

Job/Unit: O31815
/KAP1
Date: 20-02-14 11:08:49
Pages: 6
Decarboxylative Methylation of Aromatic Carboxylic Acids
1687; c) W. I. Dzik, P. P. Lange, L. J. Gooßen, Chem. Sci. 2012,
3, 2671–2678.
L. J. Gooßen, N. Rodríguez, K. Gooßen, Angew. Chem. Int.
Ed. 2008, 47, 3100–3120; Angew. Chem. 2008, 120, 3144–3164.
see: c) W. Jia, N. Jiao, Org. Lett. 2010, 12, 2000–2003; d) Y.
Zhang, S. Patel, N. Mainolfi, Chem. Sci. 2012, 3, 3196–3199.
[5] a) X. Liu, Z. Wang, X. Cheng, C. Li, J. Am. Chem. Soc. 2012,
134, 14330–14333; b) Z. Wang, L. Zhu, F. Yin, Z. Su, Z. Li,
C. Li, J. Am. Chem. Soc. 2012, 134, 4258–4263; c) F. Yin, Z.
Wang, Z. Li, C. Li, J. Am. Chem. Soc. 2012, 134, 10401–10404;
d) R. Shang, Z.-W. Yang, Y. Wang, S.-L. Zhang, L. Liu, J. Am.
Chem. Soc. 2010, 132, 14391–14393; e) R. Shang, D.-S. Ji, L.
Chu, Y. Fu, L. Liu, Angew. Chem. Int. Ed. 2011, 50, 4470–4474;
Angew. Chem. 2011, 123, 4562–4566; f) R. Shang, Z. Huang, L.
Chu, Y. Fu, L. Liu, Org. Lett. 2011, 13, 4240–4243.
[6] a) L. J. Gooßen, W. R. Thiel, N. Rodríguez, C. Linder, B.
Melzer, Adv. Synth. Catal. 2007, 349, 2241–2246; b) S.-L.
Zhang, Y. Fu, Y. Shang, Q.-X. Guo, L. Liu, J. Am. Chem. Soc.
2010, 132, 638–646.
[2]
[3] For reactions with halides, see: a) L. J. Gooßen, G. J. Deng,
L. M. Levy, Science 2006, 313, 662–664; b) L. J. Gooßen, N.
Rodríguez, B. Melzer, L. Linder, G. Deng, L. M. Levy, J. Am.
Chem. Soc. 2007, 129, 4824–4833; c) L. J. Gooßen, N. Rodríg-
uez, C. Linder, J. Am. Chem. Soc. 2008, 130, 15248–15249; d)
D. Zhao, C. Gao, X. Su, Y. He, J. You, Y. Xue, Chem. Commun.
2010, 46, 9049–9051; e) R. Shang, Y. Fu, Y. Wang, Q. Xu, H.
Yu, L. Liu, Angew. Chem. Int. Ed. 2009, 48, 9350–9354; Angew.
Chem. 2009, 121, 9514–9518; for reactions with organometallic
reagents, see: f) C. Feng, T.-P. Loh, Chem. Commun. 2010, 46,
4779–4781; g) J. J. Dai, J. H. Liu, D. F. Luo, L. Liu, Chem.
Commun. 2011, 47, 677–679; for reactions with C–C and C–X
multiple bonds, see: h) A. G. Myers, D. Tanaka, M. R. Man-
nion, J. Am. Chem. Soc. 2002, 124, 11250–11251; i) P. Hu, J.
Kan, W. Su, M. Hong, Org. Lett. 2009, 11, 2341–2344; j) Z.
Fu, S. Huang, W. Su, M. Hong, Org. Lett. 2010, 12, 4992–
4995; k) Y. Luo, J. Wu, Chem. Commun. 2010, 46, 3785–3787;
for protonation reactions, see: l) L. J. Gooßen, C. Linder, N.
Rodríguez, P. P. Lange, A. Fromm, Chem. Commun. 2009, 45,
7173–7175; m) P. Lu, C. Sanchez, J. Cornella, I. Larrosa, Org.
Lett. 2009, 11, 5710–5713; for reactions with C–H bonds, see:
n) A. Voutchkova, A. Coplin, N.-E. Leadbeater, R.-H.
Crabtree, Chem. Commun. 2008, 6312–6314; o) J. Zhou, P. Hu,
M. Zhang, S. J. Huang, M. Wang, W. Su, Chem. Eur. J. 2010,
16, 5876–5881; p) P. Hu, M. Zhang, X. Jie, W. Su, Angew.
Chem. Int. Ed. 2012, 51, 227–231; Angew. Chem. 2012, 124,
231–235; q) C. Wang, I. Piel, F. Glorius, J. Am. Chem. Soc.
2009, 131, 4194–4195; r) M. Li, H. Ge, Org. Lett. 2010, 12,
3464–3467; s) P. Fang, M. Li, H. Ge, J. Am. Chem. Soc. 2010,
132, 11898–11899; for cross-coupling between two carboxylic
acids, see: t) P. Hu, Y. Shang, W. Su, Angew. Chem. Int. Ed.
2012, 51, 5945–5949; Angew. Chem. 2012, 124, 6047–6051.
[4] For C–O bond formation, see: a) S. Bhadra, W. T. Dzik, L. J.
Goossen, J. Am. Chem. Soc. 2012, 134, 9938–9941; for C–S
bond formation, see: b) Z. Duan, S. Ranjit, P. Zhang, X. Liu,
Chem. Eur. J. 2009, 15, 3666–3669; for C–N bond formation,
[7] R. C. Larock, Comprehensive Organic Transformations, VCH
Publishers, New York, 1989, 96.
[8] a) J. Otera, Esterification, Wiley-VCH, Weinheim, Germany,
2003; b) J. Otera, Chem. Rev. 1993, 93, 1449–1470.
[9] J. Otera, Acc. Chem. Res. 2004, 37, 288–296.
[10] For selective reviews, see: a) H. E. Hoydonckx, D. E. De Vos,
S. A. Chavan, P. A. Jacobs, Top. Catal. 2004, 27, 83–96; b) D.
Enders, O. Niemeier, A. Henseler, Chem. Rev. 2007, 107, 5606–
5655; c) K. Ishihara, Tetrahedron 2009, 65, 1085–1109.
[11] For a review on transition-metal-catalyzed esterification, see:
F. Luo, C. Pan, J. Cheng, Synlett 2012, 23, 357–366.
[12] a) J. K. Kochi, J. Am. Chem. Soc. 1965, 87, 3609–3619; b) J. K.
Kochi, J. D. Bacha, T. W. Bethea, J. Am. Chem. Soc. 1967, 89,
6538–6547; c) J. D. Bacha, J. K. Kochi, J. Org. Chem. 1968, 33,
83–93.
[13] M. G. Moloney, E. Nettleton, K. Smithies, Tetrahedron Lett.
2002, 43, 907–909.
[14] J. E. Leffler, L. J. Story, J. Am. Chem. Soc. 1967, 89, 2333–2338.
[15] a) R. B. Sandin, W. B. McCormack, J. Am. Chem. Soc. 1945,
67, 2051–2052; b) H. Togo, M. Aoki, T. Kuramochib, M.
Yokoyama, J. Chem. Soc. Perkin Trans. 1 1993, 2417–2427.
[16] a) T. Wu, H. Zhang, G. Liu, Tetrahedron 2012, 68, 5229–5233;
b) J. Xie, P. Xu, H. Li, Q. Xue, H. Jin, Y. Cheng, C. Zhu, Chem.
Commun. 2013, 49, 5672–5674.
Received: December 6, 2013
Published Online: ᭿
Eur. J. Org. Chem. 0000, 0–0
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
5

Job/Unit: O31815
/KAP1
Date: 20-02-14 11:08:49
Pages: 6
Y. Jiang, S. Pan, Y. Zhang, J. Yu, H. Liu
SHORT COMMUNICATION
Decarboxylation
The acetate of PhI(OAc)2 can undergo de-
carboxylation selectively in the presence of
aromatic carboxylic acids through a radical
mechanism, and the resulting methyl rad-
ical may methylate a range of aryl acids
with the aid of copper and acetic anhydride
to afford methyl acetates. This novel reac-
Y. Jiang, S. Pan, Y. Zhang,* J. Yu,
H. Liu ............................................... 1–6
Copper-Catalyzed Decarboxylative Meth-
ylation of Aromatic Carboxylic Acids with
PhI(OAc)2
tion demonstrates
strategy through the decarboxylation of
alkyl carboxylic acids.
a new esterification
Keywords: Synthetic methods / Decarb-
oxylation / Methylation / Carboxylic acids /
Copper / Radicals
6
www.eurjoc.org
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 0000, 0–0