O-Trifluoromethylation of Phenols: Access to Aryl Trifluoromethyl Ethers by O-Carboxydifluoromethylation and Decarboxylative Fluorination

Article abstract of DOI:10.1021/acs.orglett.6b01779

A new strategy for the synthesis of aryl trifluoromethyl ethers (ArOCF₃) by combining O-carboxydifluoromethylation of phenols and subsequent decarboxylative fluorination is reported. This protocol allows easy construction of functionalized trifluoromethoxybenzenes and trifluoromethylthiolated arenes (ArSCF₃) in moderate to good yields. Moreover, it utilizes accessible and inexpensive reagents sodium bromodifluoroacetate and SelectFluor II and, thus, is practical for O-trifluoromethylation of phenols. The potential application of this method is demonstrated with the preparation of a plant-growth regulator, Flurprimidol.

Full text of DOI:10.1021/acs.orglett.6b01779

Letter
pubs.acs.org/OrgLett
O‑Trifluoromethylation of Phenols: Access to Aryl Trifluoromethyl
Ethers by O‑Carboxydifluoromethylation and Decarboxylative
Fluorination
Min Zhou, Chuanfa Ni, Zhengbiao He, and Jinbo Hu*
Key Laboratory of Organofluorine Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 345 Lingling
Road, Shanghai 200032, China
S
* Supporting Information
ABSTRACT: A new strategy for the synthesis of aryl
trifluoromethyl ethers (ArOCF3) by combining O-carboxydi-
fluoromethylation of phenols and subsequent decarboxylative
fluorination is reported. This protocol allows easy construction
of functionalized trifluoromethoxybenzenes and trifluoro-
methylthiolated arenes (ArSCF3) in moderate to good yields.
Moreover, it utilizes accessible and inexpensive reagents
sodium bromodifluoroacetate and SelectFluor II and, thus, is practical for O-trifluoromethylation of phenols. The potential
application of this method is demonstrated with the preparation of a plant-growth regulator, Flurprimidol.
through Qing’s oxidative trifluoromethylation with Ruppert-
ryl trifluoromethyl ethers (ArOCF3) have attracted
Aconsiderable attention in both academia and industry Prakash reagent (Me3SiCF3) under the promotion of a silver
salt (Scheme 1a),3 or through electrophilic trifluoromethylation
with Umemoto’s oxonium reagent or Togni’s hypervalent
iodine reagents (Scheme 1b).4 Conventionally, the synthesis of
aryl trifluoromethyl ethers applies two-step procedures: O-
carbonfunctionalization followed by tri- or difluorination
(Scheme 1c and 1d).5 However, these methods usually proceed
under harsh conditions with low efficiency because the
formation of several C−F bonds is required. Therefore,
practical methods for trifluoromethylation of phenols are still
desirable.
Considering that the O-difluoroalkylation of phenols usually
proceeds more readily than O-trifluoromethylation, we
envisioned that the O-trifluoromethylation of phenols may be
achieved through the introduction of a CF2 moiety followed by
monofluorination (Scheme 1e). Indeed, there have been
sporadic examples on the displacement of a functional group
in ArOCF2X (X = Br, Cl, SMe) by fluorine to afford ArOCF3;
however, the tedious routes to prepare ArOCF2X and the harsh
fluorination conditions impeded their broad applications.5f−h,6
To our knowledge, there has been no report on the
fluorodecarboxylation of ArOCF2CO2H to construct
ArOCF3.7 Herein, we disclose the development of a new
method for O-trifluoromethylation of phenols by combining an
effective O-carboxydifluoromethylation reaction and an opera-
tionally simple silver-catalyzed decarboxylative fluorination
reaction. This two-step O-trifluoromethylation employs the
readily available sodium bromodifluoroacetate, SelectFluor II,
and a catalytic amount of silver salt, thus providing a practical
method to access aryl trifluoromethyl ethers.
owing to the unique characteristics of the OCF3 group.1 Over
the past decades, both trifluoromethoxylation of aromatics and
O-trifluoromethylation of phenols have been developed to
access ArOCF3.2−6 The trifluoromethoxylation of aromatics,
including radical trifluoromethoxylation of arenes with
CF3OF,2b nucleophilic trifluoromethoxylation of arynes with
trifluoromethoxylate salts (CF3OM),2a oxidative trifluoro-
methoxylation of arylstannanes and arylboronic acids with
CF3OM,2c and intramolecular trifluoromethoxy migration of N-
aryl-N-trifluoromethoxylamine derivatives,2d−f suffers from
limitations such as requirement of toxic/thermally labile
reagents and limited substrate scopes. The O-trifluoromethy-
lation (Scheme 1) becomes a promising strategy owing to the
availability of many trifluoromethylation methods.3−5 However,
unlike the analogous S-trifluoromethylation, the direct O-
trifluoromethylation is challenging due to the “hard” nature of
the oxygen atom. Only very recently have several examples on
direct trifluoromethylation of phenols been reported, either
Scheme 1. Strategies for O-Trifluoromethylation of Phenols
Received: June 19, 2016
© XXXX American Chemical Society
A
DOI: 10.1021/acs.orglett.6b01779
Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
Letter
a
We began with the preparation of aryloxydifluoroacetic acids
(ArOCF2COOH) from the sodium salts of phenols (ArONa)
via a substitution reaction (Scheme 2). Initially, sodium
Scheme 3. O-Trifluoromethylation of Various Phenols
Scheme 2. O-Carboxydifluoromethylation of Phenols
chlorodifluoroacetate (ClCF2COONa) was chosen as the
source of the difluoroalkyl moiety.8 Thus, heating the mixture
of ArONa and ClCF2COONa in nonpolar solvent 1,4-dioxane
at 120 °C followed by acidification afforded both electron-
neutral and -rich aryloxydifluoroacetic acids in high yields.
However, we found that this protocol is less efficient for the
preparation of electron-deficient aryloxydifluoroacetic acids due
to decreased nucleophilicity of the phenolates. To overcome
this limitation, the more reactive BrCF2COONa was employed
instead of ClCF2COONa as a general carboxydifluoro-
methylation reagent, and a wide range of aryloxydifluoroacetic
acids 2a−x were prepared in excellent yields from the
corresponding phenolates (see Scheme 3a). In the cases of
phenolates with electron-donating substituents, the reaction
temperature could be decreased to 60 °C (2b−d, 2f−i, 2n).
Subsequently, with PhOCF2COOH (2a) as a model
substrate, we set out to explore the optimal fluorodecarbox-
ylation conditions (Table 1). Recently, decarboxylative radical
fluorination of carboxylic acids has been well established to be
efficient for the synthesis of alkyl fluorides under mild
conditions.9,10 Li and co-workers have elegantly showed that
under the catalysis of AgNO3, aliphatic carboxylic acids undergo
fluorodecarboxylation with the electrophilic fluorination
reagent SelectFluor.9a However, the fluorination of difluoro-
acetic acids with an aryloxy substituent is still underexplored,
and our initial attempts showed that the reported optimized
conditions for the fluorination of normal aliphatic carboxylic
acids with SelectFluor9a−d are not applicable for the trans-
formation of our difluoroacetic acids such as 2a (see the
Supporting Information (SI), section 7). Thus, an exhaustive
screening of fluorination reagents, metal catalysts, and solvents
was undertaken (see the SI, section 7). It was shown that,
under silver catalysis, SelectFluor II11 was a proper reagent for
converting 2a to trifluoromethyl ether 3a. The reaction
conducted with AgNO3 (20 mol %) and SelectFluor II (2.0
equiv) in the mixed solvent system CH2Cl2/H2O (1:1, v/v)
afforded the desired product 3a in 42% yield (Table 1, entry 1).
Further optimization of the ratio of CH2Cl2/H2O to 10:1 was
beneficial to this reaction (Table 1, entries 1−5). Screening on
silver salts showed that other silver salts, such as AgOTf, AgPF6,
AgBF4, and Ag2SO4, exhibited similar catalytic reactivity as
AgNO3 (see the SI, section 8), and AgI significantly improved
the yield (entry 6). However, silver salts AgCl, AgBr, and
Ag(Phen)2OTf (Phen = 1,10-phenanthroline) were less
efficient than AgNO3 (see the SI, section 8). Additional
screening of additives showed that HBF4 aq (50% w/w) (3.0
equiv) could improve the AgNO3-catalyzed reaction to a yield
as high as that with AgI alone (entry 7); nevertheless, the
catalysis with AgI was somewhat inhibited by the added HBF4
(entry 8). The reaction could also be conducted under
nonmetal catalysis when xenon difluoride (XeF2) was used as
the fluorination reagent,10a−d but with formation of a significant
a
Unless otherwise noted, the yield given refers to the isolated yield of
b
the analytically pure compound. Condition A: 2 (0.5 mmol),
SelectFluor II (2.0 equiv), AgNO3 (20 mol %), HBF4 (aq) (3.0 equiv),
CH2Cl2/H2O (10:1), 80 °C, 12 h; Condition B: 2 (0.5 mmol),
SelectFluor II (2.0 equiv), AgI (20 mol %), CH2Cl2 /H2O (10:1), 80
°C, 12 h; Condition C: 2 (0.5 mmol), SelectFluor II (3.5 equiv),
AgNO3 (20 mol %), HOTf (3.0 equiv), PhCF3/H2O (10:1), 80 °C, 24
h; Condition D: 2 (0.5 mmol), SelectFluor II (3.5 equiv), AgNO3 (20
mol %), HOTf (3.0 equiv), CF2ClCFCl2/H2O (10:1), 80 °C, 24 h.
c
Conditions: 1 (3.0 mmol), NaH (1.1 equiv), BrCF2COONa (1.1
d
e
equiv), dioxane (0.2 M), 60 °C. 80 °C instead of 60 °C. Conditions:
1 (3.0 mmol), NaH (1.2 equiv), BrCF2COONa (1.5 equiv), 100 °C.
f
19F NMR yield with PhCF3, PhSCF3 or 1,3,5-trifluorobenzene as an
g
h
internal standard. SelectFluor II (2.5 equiv). SelectFluor II (3.0
equiv). SelectFluor II (3.5 equiv). AgNO3(5 mol %).
i
j
amount of difluoromethyl ether as the side product (entry 9;
see the SI, section 7).
With two sets of optimized decarboxylative fluorination
conditions in hand (condition A: Table 1, entry 7; condition B:
entry 6), we explored the scope of this trifluoromethylation
method with respect to the phenols. As shown in Scheme 3a,
with the exception of methoxy-substituted phenols (3n), both
moderately electron-rich substrates with alkyl/aryl substituents
(3b−3i, condition B) and moderately electron-deficient
substrates with acetyl/halogen substituents (3j−3m, condition
A or B) smoothly underwent the sequence of O-carboxy-
difluoromethylation and fluorodecarboxylation to give the O-
trifluoromethylation products in moderate yields. In the cases
of alkyl-substituted phenols, functional groups such as ether,
ketone, ester, and amide were tolerated under the acid-free,
fluorodecarboxylation conditions (3f−3i). As for the methoxy-
substituted phenol, the fluorodecarboxylation failed to give the
B
DOI: 10.1021/acs.orglett.6b01779
Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
Letter
a
Table 1. Optimization on the Reaction Conditions for
Fluorodecarboxylation of PhOCF2COOH
Scheme 4. S-Trifluoromethylation of Aryl Thiophenol
a
b
entry
AgX
solvent (v/v)
additive
yield (%)
c
1
AgNO3
AgNO3
AgNO3
AgNO3
AgNO3
AgI
CH2Cl2/H2O (1:1)
CH2Cl2/H2O (4:1)
CH2Cl2/H2O (10:1)
CH2Cl2
−
−
−
−
−
−
HBF4
HBF4
−
42
57
66
0
2
3
4
5
6
7
8
a
Unless otherwise noted, the yield given refers to the isolated yield of
b
the analytically pure compound. Condition A: 2 (0.5 mmol),
SelectFluor II (2.0 equiv), AgNO3 (20 mol %), HBF4 (aq) (3.0 equiv),
CH2Cl2/H2O (10:1), 80 °C, 12 h; Condition C: 2 (0.5 mmol),
SelectFluor II (3.5 equiv), AgNO3 (20 mol %), HOTf (3.0 equiv),
H2O
0
CH2Cl2/H2O (10:1)
CH2Cl2/H2O (10:1)
CH2Cl2/H2O (10:1)
CH2Cl2
79
78
50
33(21)
AgNO3
AgI
c
PhCF3/H2O (10:1), 80 °C, 24 h. Conditions: 1 (3.0 mmol), NaH
d
9
−
(1.1 equiv), BrCF2COONa (1.1 equiv), dioxane (0.2 M), 80 °C.
d
e
NaH (1.2 equiv), BrCF2COONa (1.5 equiv), 100 °C. 19F NMR
a
Reaction conditions: 2a (0.1 mmol), SelectFluor II (0.2 mmol), AgX
f
b
yield with PhCF3 as an internal standard. SelectFluor II (3.0 equiv).
(0.02 mmol), solvent (1.0 mL), 80 °C, 12 h. Yields were determined
c
by 19F NMR spectroscopy using PhCF3 as an internal standard. 55
d
°C. XeF2 was used as the fluorination reagent. Reaction conditions:
2a (0.1 mmol), XeF2 (0.1 mmol), CH2Cl2 (2.0 mL), rt, 15 h. The yield
Scheme 5. Synthesis of Flurprimidol (10)
of PhOCF2H was given in the parentheses.
trifluoromethyl ether due to the ready fluorination on the
electron-rich aromatic ring (3n).9i However, the aforemen-
tioned optimized conditions (conditions A and B) are not
applicable to the transformation of substrates with ester,
trifluoromethyl, benzoyl, and polyhalogen substituents on the
aromatic ring due to the rather sluggish fluorodecarboxylation
(3o−3w). A further screening of the reaction conditions
showed that a switch of the organic solvent could significantly
accelerate the fluorination. Thus, performing the AgNO3-
catalyzed fluorodecarboxylation in PhCF3/H2O (10:1, v/v)
(condition C) or CF2ClCFCl2/H2O (10:1, v/v) (condition D)
as the solvent with triflic acid (3.0 equiv) as the additive
provided the desired trifluoromethyl ethers (3o−3w) in 52−
74% yields. Trifluoromethyl ethers of monohalogenated
phenols were also successfully prepared by using PhCF3/H2O
(10:1, v/v) as the solvent (3x).
The trifluoromethylation of phenols can be performed by
using the crude aryloxydifluoroacetic acids (Scheme 3b). Thus,
a liquid−liquid extraction of the aryloxydifluoroacetic acids with
CH2Cl2/H2O to remove the bromide ion followed by silver-
catalyzed decarboxylative fluorination afforded the trifluoro-
methyl ethers in overall yields similar to those performed with
purified aryloxydifluoroacetic acids.
This two-step trifluoromethylation method is also applicable
to the transformation of thiophenols. As shown in Scheme 4,
the arylthiodifluoroacetic acids derived from the corresponding
thiophenols were readily converted to the trifluoromethyl
sulfides (5a−5e). The influence of the electronic nature of the
substituents on the aromatic ring is in line with the reaction of
aryloxydifluoroacetic acids.
To demonstrate the synthetic value of our method, we
synthesized Flurprimidol 10 (Scheme 5), a plant-growth
regulator,12 which exhibits activity in a wide range of mono-
and dicotyledonous species. After difluoroacetic acid 8 was
prepared in excellent yield, its decarboxylative fluorination was
carried out on a gram scale under the optimized conditions
(condition C) to give trifluoromethyl ether 9 in moderate yield.
Subsequent nucleophilic carbonyl addition of 9 with 5-
pyrimidyllithium gave 10 in good yield. It is worth noting
that the whole process employs inexpensive reagents, which
serves as a promising alternative synthetic route to
Flurprimidol.
In summary, we have developed an expedient synthesis of
aryl trifluoromethyl ethers (ArOCF3) from phenols by
combining O-carboxydifluoromethylation and silver-catalyzed
decarboxylative fluorination. This two-step method utilizes
readily accessible reagents sodium bromodifluoroacetate and
SelectFluor II and is operationally simple and, thus, is practical
for the synthesis of various aryl trifluoromethyl ethers. We also
demonstrated the potential application of this method in the
synthesis of a plant-growth regulator, Flurprimidol.
ASSOCIATED CONTENT
■
S
* Supporting Information
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.or-
glett.6b01779.
Experimental procedures and characterization data for
products (PDF)
AUTHOR INFORMATION
■
Corresponding Author
*E-mail: jinbohu@sioc.ac.cn.
Notes
The authors declare no competing financial interest.
C
DOI: 10.1021/acs.orglett.6b01779
Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
Letter
(9) (a) Yin, F.; Wang, Z.; Li, Z.; Li, C. J. Am. Chem. Soc. 2012, 134,
10401. (b) Patel, N. R.; Flowers, R. A. J. Org. Chem. 2015, 80, 5834.
(c) Mizuta, S.; Stenhagen, I. S. R.; O’Duill, M.; Wolstenhulme, J.;
Kirjavainen, A. K.; Forsback, S. J.; Tredwell, M.; Sandford, G.; Moore,
P. R.; Huiban, M.; Luthra, S. K.; Passchier, J.; Solin, O.; Gouverneur,
V. Org. Lett. 2013, 15, 2648. (d) Ventre, S.; Petronijevic, F. R.;
MacMillan, D. W. C. J. Am. Chem. Soc. 2015, 137, 5654. (e) Leung, J.
C. T.; Sammis, G. M. Eur. J. Org. Chem. 2015, 2015, 2197. (f) Huang,
X.; Liu, W.; Hooker, J. M.; Groves, J. T. Angew. Chem., Int. Ed. 2015,
54, 5241. (g) Rueda-Becerril, M.; Mahe, O.; Drouin, M.; Majewski, M.
B.; West, J. G.; Wolf, M. O.; Sammis, G. M.; Paquin, J. F. J. Am. Chem.
Soc. 2014, 136, 2637. (h) Rueda-Becerril, M.; Sazepin, C. C.; Leung, J.
C.; Okbinoglu, T.; Kennepohl, P.; Paquin, J. F.; Sammis, G. M. J. Am.
Chem. Soc. 2012, 134, 4026. (i) Leung, J. C.; Chatalova-Sazepin, C.;
West, J. G.; Rueda-Becerril, M.; Paquin, J. F.; Sammis, G. M. Angew.
Chem., Int. Ed. 2012, 51, 10804. (j) Wu, X.; Meng, C.; Yuan, X.; Jia, X.;
Qian, X.; Ye, J. Chem. Commun. 2015, 51, 11864. (k) Phae-nok, S.;
Soorukram, D.; Kuhakarn, C.; Reutrakul, V.; Pohmakotr, M. Eur. J.
Org. Chem. 2015, 2015, 2879. (l) Sammis, G.; Paquin, J.-F.; Chatalova-
Sazepin, C.; Hemelaere, R. Synthesis 2015, 47, 2554. (m) Li, J.; Li, Y.-
L.; Jin, N.; Ma, A.-L.; Huang, Y.-N.; Deng, J. Adv. Synth. Catal. 2015,
357, 2474. (n) Johnson, R. G.; Ingham, R. K. Chem. Rev. 1956, 56,
219.
(10) For early reports on decarboxylative fluorination, see:
(a) Patrick, T. B.; Johri, K. K.; White, D. H. J. Org. Chem. 1983, 48,
4158. (b) Patrick, T. B.; Johri, K. K.; White, D. H.; Bertrand, W. S.;
Mokhtar, R.; Kilbourn, M. R.; Welch, M. J. Can. J. Chem. 1986, 64,
138. (c) Patrick, T. B.; Khazaeli, S.; Nadji, S.; Hering-Smith, K.; Reif,
D. J. Org. Chem. 1993, 58, 705. (d) Ramsden, C. A.; Shaw, M. M.
Tetrahedron Lett. 2009, 50, 3321. (e) Grakauskas, V. J. Org. Chem.
1969, 34, 2446.
(11) For small scale use in laboratory, SelectFluor II can be prepared
from N-fluorobenzenesulfonimide (NFSI), 1,4-diazabicyclo[2.2.2]-
octane (DABCO), and CH3I; for details, see the SI, section 4.
(12) Benefiel, R. L.; Krumkalns, E. V. US 4002628 (to Elli Lilly and
Co., USA; Jan. 11, 1977; filed on Dec. 17, 1975); Chem. Abstr. 1977,
86, 155686.
ACKNOWLEDGMENTS
■
This work was supported by the National Basic Research
Program of China (2015CB931900, 2012CB215500), the
National Natural Science Foundation of China (21372246,
21421002, 21472221, 21402227), the Chinese Academy of
Sciences, Shanghai Academic Research Leader Program
(15XD1504400), Shanghai Rising-Star Program
(16QA1404600), and the Youth Innovation Promotion
Association CAS (2014231) for financial support.
REFERENCES
■
(1) (a) Mcclinton, M. A.; Mcclinton, D. A. Tetrahedron 1992, 48,
6555. (b) Hansch, C.; Leo, A.; Taft, R. W. Chem. Rev. 1991, 91, 165.
(c) Smart, B. E. J. Fluorine Chem. 2001, 109, 3. (d) Hansch, C.; Leo, A.
Substituent Constants for Correlation Analysis in Chemistry and Biology;
Wiley: New York, 1979. (e) Federsel, D.; Herrmann, A.; Christen, D.;
Sander, S.; Willner, H.; Oberhammer, H. J. Mol. Struct. 2001, 567-568,
127. For application of the OCF3 group, see: (f) Leroux, F.; Jeschke,
P.; Schlosser, M. Chem. Rev. 2005, 105, 827. (g) Jeschke, P.; Baston,
E.; Leroux, F. R. Mini-Rev. Med. Chem. 2007, 7, 1027. (h) Landelle, G.;
Panossian, A.; Leroux, F. R. Curr. Top. Med. Chem. 2014, 14, 941.
(i) Valsasina, B.; Beria, I.; Alli, C.; Alzani, R.; Avanzi, N.; Ballinari, D.;
Cappella, P.; Caruso, M.; Casolaro, A.; Ciavolella, A.; Cucchi, U.; De
Ponti, A.; Felder, E.; Fiorentini, F.; Galvani, A.; Gianellini, L. M.;
Giorgini, M. L.; Isacchi, A.; Lansen, J.; Pesenti, E.; Rizzi, S.; Rocchetti,
M.; Sola, F.; Moll. Mol. Cancer Ther. 2012, 11, 1006. (j) Sagheer, M.;
Yasir, M.; Mansoor-ul-Hasan; Ashfaq, M. Pak. J. Agr. Sci. 2012, 49, 173.
(k) Kirsch, P.; Bremer, M. Angew. Chem., Int. Ed. 2000, 39, 4216.
(l) Mamada, M.; Shima, H.; Yoneda, Y.; Shimano, T.; Yamada, N.;
Kakita, K.; Machida, T.; Tanaka, Y.; Aotsuka, S.; Kumaki, D.; Tokito,
S. Chem. Mater. 2015, 27, 141.
(2) (a) Kolomeitsev, A. A.; Vorobyev, M.; Gillandt, H. Tetrahedron
Lett. 2008, 49, 449. (b) Venturini, F.; Navarrini, W.; Famulari, A.;
Sansotera, M.; Dardani, P.; Tortelli, V. J. Fluorine Chem. 2012, 140, 43.
(c) Huang, C. H.; Liang, T.; Harada, S.; Lee, E.; Ritter, T. J. Am. Chem.
Soc. 2011, 133, 13308. (d) Hojczyk, K. N.; Feng, P.; Zhan, C.; Ngai,
M.-Y. Angew. Chem., Int. Ed. 2014, 53, 14559. (e) Feng, P.; Lee, K. N.;
Lee, J. W.; Zhan, C.; Ngai, M.-Y. Chem. Sci. 2016, 7, 424. (f) Lee, K.
N.; Lee, J. W.; Ngai, M.-Y. Synlett 2016, 27, 313. (g) Umemoto, T.,
Zhou, M., Hu, J. CN201510431545.2, 2016.
(3) Liu, J.-B.; Chen, C.; Chu, L.; Chen, Z.-H.; Xu, X.-H.; Qing, F.-L.
Angew. Chem., Int. Ed. 2015, 54, 11839.
(4) (a) Umemoto, T.; Adachi, K.; Ishihara, S. J. Org. Chem. 2007, 72,
6905. (b) Stanek, K.; Koller, R.; Togni, A. J. Org. Chem. 2008, 73,
7678. (c) Liang, A.; Han, S.; Liu, Z.; Wang, L.; Li, J.; Zou, D.; Wu, Y.;
Wu, Y. Chem. - Eur. J. 2016, 22, 5102.
(5) (a) Yagupolskii, L. M. Dokl. Akad. Nauk SSSR 1955, 105, 100.
(b) Yarovenko, N. N.; Vasileva, A. S. Zh. Obshch. Khim. 1958, 28,
2502. (c) Yagupolskii, L. M.; Troitskaya, V. I. J. Gen. Chem. USSR
1961, 31, 845. (d) Yagupolskii, L. M.; Orda, V. V. Zh. Obshch. Khim.
1964, 34, 1979. (e) Sheppard, W. A. J. Org. Chem. 1964, 29, 1.
(f) Kuroboshi, M.; Suzuki, K.; Hiyama, T. Tetrahedron Lett. 1992, 33,
4173. (g) Kanie, K.; Tanaka, Y.; Suzuki, K.; Kuroboshi, M.; Hiyama, T.
Bull. Chem. Soc. Jpn. 2000, 73, 471. (h) Kuroboshi, M.; Kanie, K.;
Hiyama, T. Adv. Synth. Catal. 2001, 343, 235.
(6) (a) Hagooly, Y.; Sasson, R.; Welch, M. J.; Rozen, S. Eur. J. Org.
Chem. 2008, 2008, 2875. (b) Khotavivattana, T.; Verhoog, S.;
Tredwell, M.; Pfeifer, L.; Calderwood, S.; Wheelhouse, K.; Lee
Collier, T.; Gouverneur, V. Angew. Chem., Int. Ed. 2015, 54, 9991.
(7) After the submission of this paper, a similar fluorodecarboxylation
using a stoichiometric amount of AgF2 was published online; see:
Zhang, Q.-W.; Brusoe, A. T.; Mascitti, V.; Hesp, K. D.; Blakemore, D.
C.; Kohrt, J. T.; Hartwig, J. F. Angew. Chem., Int. Ed. 2016,
DOI: 10.1002/anie.201604793.
(8) (a) Fretz, H. Tetrahedron 1998, 54, 4849. (b) Salomon, P.; Zard,
S. Z. Org. Lett. 2014, 16, 1482.
D
DOI: 10.1021/acs.orglett.6b01779
Org. Lett. XXXX, XXX, XXX−XXX