Catalyst-free and catalytic Friedel-Crafts alkylations of indoles in Solkane 365mfc, an environmentally benign alternative solvent

Article abstract of DOI:10.1039/c0gc00619j

Solkane 365mfc is a proven environmentally benign alternative solvent for catalyst-free Friedel-Crafts (F-C) alkylations of indoles with trifluoropyruvate and glyoxylate. Their enantioselective variants are also achieved by virtue of the high-affinity of fluorous cinchona alkaloids catalysts to Solkane 365mfc to provide F-C adducts in excellent yields with good to excellent ees (up to 96% ee).

Full text of DOI:10.1039/c0gc00619j

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COMMUNICATION
Catalyst-free and catalytic Friedel–Crafts alkylations of indoles in
R
Solkaneꢀ 365mfc, an environmentally benign alternative solvent†
Xiu-Hua Xu, Akihiro Kusuda, Etsuko Tokunaga and Norio Shibata*
Received 29th September 2010, Accepted 8th November 2010
DOI: 10.1039/c0gc00619j
R
Solkaneꢀ 365mfc is a proven environmentally benign
alternative solvent for catalyst-free Friedel–Crafts (F–C)
alkylations of indoles with trifluoropyruvate and glyoxy-
late. Their enantioselective variants are also achieved by
virtue of the high-affinity of fluorous cinchona alkaloids
demands by “green chemistry”, the development of new envi-
ronmentally friendly solvents has created a fast-growing interest.
R
Recently, we reported for the first time that Solkaneꢀ 365mfc, a
hydrofluorocarbon (1,1,1,3,3-pentafluorobutane), developed by
Solvay Fluor GmbH, was used as an environmentally benign
alternative solvent for the nucleophilic trifluoromethylation of
aldehydes, ketones and oxazolidinone.8a Indeed, as a green
R
catalysts to Solkaneꢀ 365mfc to provide F–C adducts in
excellent yields with good to excellent ees (up to 96% ee).
R
solvent, Solkaneꢀ 365mfc is non-toxic and has no impact
9
R
whatsoever on the ozone layer. Although Solkaneꢀ 365mfc has
Introduction
a flash point below -27 ◦C, but is difficult to ignite. The minimum
ignition energy is around 50 times higher than of n-pentane and
is 10.8mJ (25 ◦C, 8 vol% in air at 1 bar).9 It is used as an insulating
and blowing agent for polyurethane foams, whose main uses are
the thermal insulation of residential and industrial buildings, as
The Friedel–Crafts (F–C) reaction and its variants are of
key importance to practising synthetic organic chemists.1 The
reaction consists of the electrophilic substitution of an aromatic
nucleus with alkyl or acyl halides, or their equivalents, in the
presence of catalysts such as Lewis acids. A combination of
arenes and electrophiles is therefore capable of providing many
structural variants of aromatic compounds for different pur-
poses. These variants involve the addition of a heteroaromatic
p nucleophile to a ketone or activated alkene electrophile.2
Among heteroaromatic systems, indoles have received much
attention,3 since they are important structural motifs frequently
encountered in biologically-active natural products, as well as in
pharmaceuticals and agrochemicals. The most commonly used
solvents for F–C alkylations of indoles are dichloromethane,
toluene and ether. These solvents have some drawbacks such as
toxicity and peroxide formation. Increasingly tight restrictions
on the use of organic solvents in industrial synthesis4 has led us
to search for an environmentally benign alternative solvent for
the F–C reactions of indoles.5,6 Great efforts have been made
to achieve the goal of making the F–C reaction of indoles
a truly green process, while still retaining the high yield and
selectivity, using green solvents, and, better still, by avoiding
the use of any catalyst. The use of water or ionic liquids as
solvents in environmentally friendly F–C reactions of indoles has
generated considerable interest.7 The Kantam and Xiao groups
have reported examples of ionic liquids used as both solvent and
catalyst for the F–C alkylation of indoles.7k,l Following urgent
R
well as in cold storage. Solkaneꢀ 365mfc is now produced in
a pilot plant with a capacity of several hundred tons per year.
As part of our ongoing fluorine chemistry project8 concerning
R
the use of Solkaneꢀ 365mfc as a green medium in organic
reactions,8a we herein show the catalyst-free F–C alkylation
R
of indoles with trifluoropyruvate and glyoxylate in Solkaneꢀ
365mfc. Their enantioselective variants have also been achieved
by virtue of the high-affinity of fluorous cinchona alkaloids
R
catalysts to Solkaneꢀ 365mfc as a chiral source. Thus, the
catalyst-free F–C reaction and the fluorous cinchona alkaloid-
catalyzed asymmetric F–C reaction of indoles have been realized
R
in Solkaneꢀ 365mfc for the first time (Scheme 1).
Scheme 1 The catalyst-free F–C reaction and catalytic enantioselective
R
F–C reaction of indoles in Solkaneꢀ 365mfc.
Results and discussion
Catalyst-free Friedel–Crafts alkylation of indoles
Department of Frontier Materials, Graduate School of Engineering,
Nagoya Institute of Technology, Gokiso, Showa-ku, Nagoya, 466-8555,
Japan. E-mail: nozshiba@nitech.ac.jp; Fax: +81 52-735-5442
† Electronic supplementary information (ESI) available: Experimental
details. See DOI: 10.1039/c0gc00619j
Heterocyclic organofluorine compounds are receiving a great
deal of attention in pharmaceutical, agrochemical and material
sciences due to the unique features brought by the fluorine atom
to the physical and chemical features of the parent molecules.10
46 | Green Chem., 2011, 13, 46–50
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Table 1 Catalyst-free F–C alkylation of indole derivatives with ethyl
trifluoropyruvate in Solkaneꢀ 365mfc
Table 2 Catalyst-free F–C alkylation of indole derivatives and ethyl
glyoxylate in Solkaneꢀ 365mfc
R
R
Entrya
1
R
Time/h
3
Yield (%)b
Entry
1
R1
R2
Time/h
2
Yield (%)a
1
2
3
4
5
6
7
8
1a
1b
1c
1d
1e
1f
1g
1h
1i
1j
1k
1l
1m
1n
1o
1p
1q
1a
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
Me
H
1.0
0.5
0.5
2.0
0.5
0.5
1.0
2.0
2.0
1.0
0.5
0.5
0.5
1.0
1.0
2.0
0.5
0.25
2a
2b
2c
2d
2e
2f
2g
2h
2i
2j
2k
2l
2m
2n
2o
2p
2q
2a
92
91
84
83
96
96
90
91
89
95
99
99
97
94
85
96
91
96
1
2
3
4
5
6
7
8
1a
1b
1d
1e
1f
H
1.0
4.0
3.0
1.0
1.5
1.0
1.5
2.0
16.0
24.0
1.0
2.0
3a
3b
3d
3e
3f
73
89
56
66
79
56
54
82
84
29
75
73
2-Me
2-Ph
4-Me
5-Me
5-OMe
5-F
5-Cl
5-Br
5-I
6-Me
7-Me
7-Et
7-But
7-Br
7-Ph
H
2-Me
4-Me
5-Me
5-OMe
5-F
5-Cl
5-Br
1g
1h
1i
3g
3h
3i
9
9
1j
5-I
3j
10
11
12
13
14
15
16
17
18b
10
11
12
1r
1k
1l
5-CO2Me
6-Me
7-Me
3r
3k
3l
a Commercially available ethyl glyoxylate (~50 wt% in toluene) was used.
b Isolated yield by silica gel column chromatography.
H
R
Solkaneꢀ 365mfc was also found to be useful for the catalyst-
a Isolated yield by silica-gel column chromatography. b The reaction was
performed at a slightly large scale and product 2a was isolated by
distillation. Solkaneꢀ 365mfc was recovered in 81% yield. See ESI.
free F–C alkylation of indoles with ethyl glyoxylate at room
temperature to give the products in good to high yields (Table 2),
although a longer reaction time was required compared to the
reaction with ethyl trifluoropyruvate, in particular, the indole
containing an electron-withdrawing carboxylate group (Table 2,
entry 10).
R
Our initial investigation hence started with the F–C alkylation
R
of indoles with ethyl trifluoropyruvate in Solkaneꢀ 365mfc.
This transformation is usually accomplished under the catalysis
of a Lewis and Brønsted acid.6b,11 To¨ro¨k, Prakash and co-
workers have reported that the reaction of indole (1a) with ethyl
trifluoropyruvate proceeded in ether solution without using a
catalyst.6b However, the reaction times were as long as 90 h
and the reaction rates can be magnified by two orders in
Catalytic enantioselective Friedel–Crafts alkylation of indoles
Our success in the catalyst-free F–C reactions of indoles in
R
Solkaneꢀ 365mfc prompted us to extend to catalytic asym-
metric reactions (Table 3). To¨ro¨k, Prakash and co-workers
have reported that natural cinchona alkaloids catalyze the
highly enantioselective F–C alkylation of indoles with ethyl
trifluoropyruvate.6b The reaction proceeded in ether at -8 ◦C.
We thus examined whether their asymmetric catalytic system
the presence of catalyst.6b,11e To our delight, when Solkaneꢀ
R
365mfc was used as the medium, this reaction was complete
in 1 h at room temperature, without the addition of a catalyst,
giving the desired product in 92% yield (Table 1, entry 1). The
favorable outcome might be caused by the intimate interaction
R
was applicable to Solkaneꢀ 365mfc. Regrettably, the natural
cinchona alkaloids, i.e., cinchonidine (CD), cinchonine (CN),
between fluorinated compounds and fluorinated solvents, i.e.,
quinine (QN) and quinidine (QD), gave F–C adducts with
10f
R
R
ethyl trifluoropyruvate and Solkaneꢀ 365mfc, although it
much lower ee values in Solkaneꢀ 365mfc compared to ether,
is not clear. This result encouraged us to apply this system
to various substituted indoles (Table 1, entries 2–16). In all
cases, the reactions were usually complete within 0.5–2 h,
and high to excellent yields were achieved for various indole
derivatives independent of the substituents at different positions
of the indole ring. A wide range of functional groups, including
electron-withdrawing, electron-donating and neutral groups,
on the indole ring were well-tolerated. The presence of bulky
substituents on the indole ring, such as phenyl and tert-butyl,
also furnished the corresponding products in good to excellent
yields (Table 1, entries 3, 14 and 16). It is noteworthy that
this reaction proceeded with excellent yield with an N-methyl-
protected indole (Table 1, entry 17). What is more, in a slightly
large-scale preparation, the product was isolated by distillation
despite excellent yields being achieved (Table 3, entries 1–8).
This is probably due to the poor solubility of the natural
cinchona alkaloids in Solkaneꢀ 365mfc at -8 ◦C. In fact,
R
when the temperature of the QD-catalyzed F–C reaction of
1a was increased to rt, the selectivity increased from 22 to
48% ee (Table 3, entries 8 and 9). To further improve the
enantioselectivity, three effective catalysts 4a, 4b and 4c, reported
by the Deng group,6d were attempted to catalyze the reaction
R
in Solkaneꢀ 365mfc. However, the ee values were moderate,
46–58% (Table 3, entries 10–12). Considering that fluorinated
compounds should dissolve well in fluorinated solvents, we
designed novel fluorinated cinchona alkaloids 4d and 4e (see the
ESI† for details of their preparation). The ee values improved
slightly to 60–62% (Table 3, entries 13 and 14). Since the non-
catalytic F–C reaction of indoles with trifluoropyruvate was very
R
to give 2a in 96% yield, while Solkaneꢀ 365mfc was recovered
R
in 81% yield (Table 1, entry 18).
fast in Solkaneꢀ 365mfc, as revealed in the first part of this
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Table 3 Asymmetric F–C alkylation of indole 1a with ethyl trifluo-
ropyruvate in Solkaneꢀ 365mfc
Table 4 Catalytic enantioselective F–C alkylation of indoles with ethyl
trifluoropyruvate in Solkaneꢀ 365mfc catalyzed by 4e and 4e¢
R
R
Entrya
1
R
4
2b
Yield (%)c
ee (%)d
1
2
3
4
5
6
7
8
1a
1d
1g
1k
1l
1m
1n
1o
1p
1a
1d
1g
1k
1l
H
4-Me
5-F
6-Me
7-Me
7-Et
7-But
7-Br
7-Ph
H
4e
(S)-2a
(S)-2d
(S)-2g
(S)-2k
(S)-2l
93
84
98
88
92
97
81
80
95
98
78
99
91
99
92
86
79
93
72
48
70
55
85
81
79
79
75
71
43
56
63
77
82
80
58
74
4e
4e
4e
4e
Yield
Configura-
4e
(S)-2m
(S)-2n
(S)-2o
(S)-2p
(R)-2a
(R)-2d
(R)-2g
(R)-2k
(R)-2l
(R)-2m
(R)-2n
(R)-2o
(R)-2p
Entry Catalyst Solvent
Temperature (%)a ee (%)b tionc
4e
4e
1
2
3
4
5
6
7
8
CD
CD
CN
CN
QN
QN
QD
QD
QD
4a
Et2O
-8 ◦
C
C
C
C
C
C
C
C
91
98
97
97
98
96
94
98
98
96
89
78
98
91
91
93
76
10
62
14
77
46
64
22
48
58
50
46
62
60
70
72
S
S
R
R
S
S
R
R
R
S
S
S
S
S
S
S
9
4e
Solkaneꢀ -8 ◦
R
10
11
12
13
14
15
16
17
18
4e¢
4e¢
4e¢
4e¢
4e¢
4e¢
4e¢
4e¢
4e¢
Et2O
-8 ◦
4-Me
5-F
Solkaneꢀ -8 ◦
R
Et2O
-8 ◦
6-Me
7-Me
7-Et
7-But
7-Br
7-Ph
Solkaneꢀ -8 ◦
R
Et2O
-8 ◦
1m
1n
1o
1p
Solkaneꢀ -8 ◦
R
R
9
Solkaneꢀ rt
R
10
11
12
13
14
15d
16d
Solkaneꢀ rt
R
4b
Solkaneꢀ rt
a Trifluoropyruvate was added slowly to the reaction mixture over
1 h. b The absolute configuration was assigned by comparison with
the reported optical rotation.11g c Isolated yield by silica gel column
chromatography. d Determined by chiral HPLC analysis.
R
4c
Solkaneꢀ rt
R
4d
Solkaneꢀ rt
R
4e
Solkaneꢀ rt
R
4d
Solkaneꢀ rt
R
4e
Solkaneꢀ rt
a Isolated yield by silica gel column chromatography. b Determined by
chiral HPLC analysis. c The absolute configuration was assigned by
comparison with the reported optical rotation.11b d Trifluoropyruvate
was added slowly to the reaction mixture for 1 h.
and when 7-ethylindole reacted with catalyst 4e¢ to give the R-
isomeric product with an 82% ee (Table 4, entry 15).
Importantly, this asymmetric catalytic system was effectively
used in asymmetric F–C alkylations with ethyl glyoxylate
(Table 5). In most cases, good to excellent yields (except for 1r;
Table 5, entry 7) and good to excellent ee values were obtained
(Table 5, entries 1–9). Again, both enantiomers of the products
were selectively obtained by the choice of catalyst, 4e or 4e¢.
The reactions with 7-methylindole gave the best results for both
isomeric products with 94% and 96% ee, respectively (entry 9).
article, ethyl trifluoropyruvate was slowly added to the reaction
mixture over 1 h; ee values were improved to 70–72% (Table 3,
entries 15 and 16).
The asymmetric F–C alkylation of various indole substrates in
R
Solkaneꢀ 365mfc was next carried out to examine the generality
and scope of the reaction using catalyst 4e and its pseudo-
enantiomer 4e¢ prepared from quinine (see the ESI† for details
of the preparation) (Table 4). As can be seen in Table 4, catalysts
4e and 4e¢ proved to be effective for the asymmetric F–C reaction
Catalyst-free and Catalytic enantioselective Friedel–Crafts
R
alkylation of indoles in Solkaneꢀ 365/227 blend solvent
R
of indoles in Solkaneꢀ 365mfc to furnish the products in high
Finally, we examined the F–C reactions in commercially avail-
12
R
to excellent yields with moderate to high enantioselectivities
(Table 4, entries 1–18). It should be mentioned that both
enantiomers of the products were selectively obtained by the
choice of catalyst, 4e or 4e¢. Substituents at the 4, 5 and 6-
positions gave lower ee values compared to reactant 1a (Table 4,
entries 2–4 and 11–13), while the substituents at position 7 gave
higher ee values (Table 4, entries 5–9 and 14–18). The best results
were obtained when 7-methylindole reacted with catalyst 4e to
give the S-isomeric product with an 85% ee (Table 4, entry 5)
able Solkaneꢀ 365/227 blend solvent (365/227 = 93/7). It is
◦
R
disclosed that Solkaneꢀ 365mfc has the flash point £ -27 C;
R
however, its blend form (93/7 mixture of Solkaneꢀ 365mfc and
R
R
Solkaneꢀ 227, 1,1,1,2,3,3,3-heptafluoropropane) as Solkaneꢀ
365/227 is known to have no flash point (non-flammable)
9b
R
and could also provide the benefits of Solkaneꢀ 365mfc.
Therefore, we compared the reactivity pattern of the present F–
C alkylations of indoles with trifluoropyruvate and glyoxylate in
R
R
both solvents-Solkaneꢀ 365mfc and Solkaneꢀ 365/227. The
48 | Green Chem., 2011, 13, 46–50
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Table 5 Catalytic enantioselective F–C alkylation of indoles with ethyl
glyoxylate in Solkaneꢀ 365mfc catalyzed by 4e and 4e¢
Table 7 Catalyst-free and catalytic enantioselective F–C alkylation of
1a with ethyl glyoxylate in Solkaneꢀ 365/227
R
R
Entrya
1
R
Time/h
3
Yield (%)b
ee (%)c
Entrya Solvent
Catalyst Yield (%)b ee (%)c
1
2
3
4
5
6
7
8
9
1a
1b
1d
1e
1f
1g
1r
1k
1l
H
1.0
1.0
1.0
1.0
1.0
1.0
3.0
1.0
1.0
3a
3b
3d
3e
3f
3g
3r
3k
3l
80 (92)
99 (99)
77 (84)
99 (91)
96 (92)
74 (90)
8 (25)
90 (92)
85 (85)
89 (92)
87 (91)
83 (88)
89 (92)
81 (90)
89 (92)
94 (96)
R
1
2
3
4
5
6
Solkaneꢀ365mfc
—
—
4e
73
71
80
92
92
96
—
—
90
90
92
91
2-Me
4-Me
5-Me
5-OMe
5-F
5-CO2Me
6-Me
7-Me
R
Solkaneꢀ365/227 (93/7)
R
Solkaneꢀ365mfc
R
Solkaneꢀ365/227 (93/7) 4e
R
Solkaneꢀ365mfc
4e¢
R
Solkaneꢀ365/227 (93/7) 4e¢
a Commercially available ethyl glyoxylate (~50 wt% in toluene) was used.
b Isolated yield by silica gel column chromatography. c Determined by
chiral HPLC analysis.
79 (99)
99 (99)
a Commercially available ethyl glyoxylate (~50 wt% in toluene) was
used. b Isolated yield by silica gel column chromatography. Values in
parentheses indicate the yield catalyzed by 4e¢. c Determined by chiral
HPLC analysis. Values in parentheses indicate the ee catalyzed by 4e¢.
blend (365/227 = 93/7) is completely non-flammable. The F–
C reaction is ubiquitous and one of the key transformations, not
only in laboratory-scale chemistry, but also in industrial process
Table 6 Catalyst-free and catalytic enantioselective F–C alkylation of
1a with ethyl trifluoropyruvate in Solkaneꢀ 365/227
R
chemistry. We hope that Solkaneꢀ 365mfc will become a green
R
organic solvent of choice alongside water and ionic liquids in
industrial process chemistry. Extensions to other ubiquitous
R
organic reactions with Solkaneꢀ 365mfc as a medium is
currently under investigation.
Experimental
Entrya
Solvent
Catalyst Yield (%)b ee (%)c
Typical procedure for the catalyst-free F–C alkylation of indole
R
1a with ethyl trifluoropyruvate in Solkaneꢀ 365mfc
R
1
2
3
4
5
6
Solkaneꢀ365mfc
—
—
4e
92
97
93
91
98
89
—
—
72
73
71
72
R
Solkaneꢀ365/227 (93/7)
R
To a stirred solution of 1a (23.4 mg, 0.20 mmol) in Solkaneꢀ
R
Solkaneꢀ365mfc
R
Solkaneꢀ365/227 (93/7) 4e
365mfc (0.5 mL) was added ethyl trifluoropyruvate (29.2 mL,
0.22 mmol) at room temperature under a nitrogen atmosphere.
The mixture was stirred at room temperature for 1 h. Then,
the solvent was removed in vacuo, and the residue was purified
by column chromatography (n-hexane–ethyl acetate = 80/20) to
give 2a as a white solid (52.9 mg, 92%).
R
Solkaneꢀ365mfc
4e¢
R
Solkaneꢀ365/227 (93/7) 4e¢
a Trifluoropyruvate was added slowly to the reaction mixture over 1 h
(entries 3–6). b Isolated yield by silica gel column chromatography.
c Determined by chiral HPLC analysis.
results are shown in Table 6 and Table 7. As might be expected,
reactivity behaviour such as reaction rates, chemical yields and
Typical procedure for the catalytic enantioselective F–C
R
alkylation of indole 1a with ethyl trifluoropyruvate in Solkaneꢀ
R
enantioselectivity were almost identical in Solkaneꢀ 365mfc
365mfc
R
and Solkaneꢀ 365/227.
To a stirred solution of 1a (11.7 mg, 0.10 mmol) and catalyst 4e
R
(8.2 mg, 0.01 mmol) in Solkaneꢀ 365mfc (0.3 mL) was added
Conclusions
R
slowly ethyl trifluoropyruvate (14.6 mL, 0.11 mmol) in Solkaneꢀ
R
365mfc (0.2 mL) over 1 h at room temperature under a nitrogen
atmosphere. The mixture was stirred at room temperature for
1 h. Then the solvent was removed in vacuo, and the residue was
purified by column chromatography (n-hexane–ethyl acetate =
80/20) to give (S)-2a as a white solid (26.6 mg, 93%, 72% ee).
The environmentally benign solvent Solkaneꢀ 365mfc is in-
troduced as a medium for the first time for the F–C reaction
of indoles with trifluoropyruvate and glyoxylate. The reaction
R
proceeds nicely in Solkaneꢀ 365mfc at rt without any help
from a promoter. Enantioselective variants of this reaction have
also been achieved by virtue of the high-affinity of fluorous
R
cinchona alkaloid catalysts to Solkaneꢀ 365mfc to afford the
Acknowledgements
desired products in excellent yields with good to excellent ee
R
values. Solkaneꢀ 365mfc is also useful for both catalyst-free
This study was financially supported in part by Grants-in-Aid
for Scientific Research (B21390030, 22106515) and the Chubu
Bureau of Economy Trade and Industry. We thank Dr Max
Braun and Mr Toyofuku Yoshitaka, Solvay Fluor GmbH, for
and catalytic F–C reactions, even in the presence of 7 vol%
R
of Solkaneꢀ 227, which provides additional benefits from a
R
green chemistry point of view, since the Solkaneꢀ 365/227
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Green Chem., 2011, 13, 46–50 | 49
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R
R
the generous gift of Solkaneꢀ 365mfc and Solkaneꢀ 365/227.
We are also grateful to Central Glass Co. Ltd. for a gift of ethyl
trifluoropyruvate.
16, 1664; (o) F.-F. Guo, G.-Y. Liu, S.-S. Xiong, S.-J. Wang and Z. Y.
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Notes and references
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2 For reviews, see: (a) M. Bandini, A. Melloni and A. Umani-Ronchi,
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3 For reviews, see: M. Bandini and A. Eichholzer, Angew. Chem., Int.
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& Francis, Boca Raton, FL, 2008.
5 Solvent-free systems are obviously another solution; however, the
solvent-free F–C alkylation of indoles only relies on racemic synthesis
and might not be applied for enantioselective F–C reactions. See:
(a) J.-L. Zhao, L. Liu, H.-B. Zhang, Y.-C. Wu, D. Wang and Y.-J.
Chen, Synlett, 2006, 96; (b) J.-L. Zhao, L. Liu, H.-B. Zhang, Y.-C.
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Tabatabaeian, M. Mamaghani, N. O. Mahmoodi and A. Khorshidi,
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320.
6 For recent examples of the enantioselective F–C alkylation of indoles,
see: (a) M. Bandini, P. G. Cozzi, P. Melchiorre and A. Umani-Ronchi,
Angew. Chem., Int. Ed., 2004, 43, 84; (b) B. To¨ro¨k, M. Abid, G.
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Prakash, Angew. Chem., Int. Ed., 2005, 44, 3086; (c) S. Shirakawa, R.
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R
9 (a) See Solvay Solkaneꢀ 365 mfc brochure: http://www.solvay-
fluor.com/product/lib/0,0,-_EN-1000798,00.html;
(b)
See
R
Solvay Solkaneꢀ 365/227 brochure: http://www.solvay-
fluor.com/product/lib/0,0,-_EN-1000292,00.html.
10 (a) I. Ojima, J. R. McCarthy, J. T. Welch, in Biomedical Frontiers
of Fluorine Chemistry, American Chemical Society, Washington,
DC, 1996; (b) T. Himaya, Organofluorine Compounds, Springer-
Verlag, Berlin, Feidelberg, 2001; (c) K. Uneyama, in Organofluorine
Chemistry, Blackwell, Oxford, 2006; (d) L. Paquette, in Fluorine-
Containing Reagents, Wiley-VCH, Weinheim, 2007; (e) J.-A. Ma and
D. Cahard, Chem. Rev., 2008, 108, PR1; (f) P. Kirsch, in Modern
Fluoroorganic Chemistry, Wiley-VCH, Weinheim, 2004.
11 (a) N. Gathergood, W. Zhuang and K. A. Jørgensen, J. Am. Chem.
Soc., 2000, 122, 12517; (b) W. Zhuang, N. Gathergood, R. G. Hazell
and K. A. Jørgensen, J. Org. Chem., 2001, 66, 1009; (c) G. K. S.
Prakash, P. Yan, B. To¨ro¨k and G. A. Olah, Synlett, 2003, 527; (d) M.
P. A. Lyle, N. D. Draper and P. D. Wilson, Org. Lett., 2005, 7, 901;
(e) M. Abid and B. To¨ro¨k, Adv. Synth. Catal., 2005, 347, 1797;
(f) M. Soueidan, J. Collin and R. Gil, Tetrahedron Lett., 2006, 47,
5467; (g) S. Nakamura, K. Hyodo, Y. Nakamura, N. Shibata and T.
Toru, Adv. Synth. Catal., 2008, 350, 1443; (h) J. Nie, G.-W. Zhang,
L. Wang, A.-P. Fu, Y. Zheng and J.-A. Ma, Chem. Commun., 2009,
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J.-A. Ma, Eur. J. Org. Chem., 2009, 3145; (j) H.-M. Dong, H.-H. Lu,
L.-Q. Lu, C.-B. Chen and W.-J. Xiao, Adv. Synth. Catal., 2007, 349,
1597.
R
12 The idea of testing the F–C reaction in Solkaneꢀ 365/227 blend
R
solvent in order to provide additional benefits of Solkaneꢀ 365mfc
was kindly suggested by a reviewer of this manuscript.
50 | Green Chem., 2011, 13, 46–50
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