Synthesis of Aryl Triflones through the Trifluoromethanesulfonylation of Benzynes

Article abstract of DOI:10.1002/open.201700204

The direct synthesis of aryl triflones, that is, trifluoromethanesulfonyl arenes, was achieved through the trifluoromethanesulfonylation of benzynes. The trifluoromethanesulfonyl group, one of the fluorinated functional groups, is a highly electron-negative and mild lipophilic substituent. Aryl triflones have high potential in the synthesis of bioactive compounds and specialty materials. The treatment of 2-(trimethylsilyl)aryl trifluoromethanesulfonates with cesium fluoride in the presence of 15-crown-5 generated benzynes, which reacted with sodium trifluoromethanesulfinate followed by protonation with tBuOH under heating conditions, provided aryl triflones in moderated to good yields. Both symmetrical and unsymmetrical triflones were nicely accessed under the same reaction conditions. Interestingly, the trifluoromethanesulfonylation of unsymmetrical benzyne precursors proceeded smoothly to furnish corresponding aryl triflones in good yields with good to high regioselectivities. The balance of polarization of electric charge as well as steric hindrance of the benzyne intermediates are central factors to control the outcome of regioselectivity.

Full text of DOI:10.1002/open.201700204

DOI: 10.1002/open.201700204
Synthesis of Aryl Triflones through the
Trifluoromethanesulfonylation of Benzynes
Yuji Sumii,[a] Yutaka Sugita,[a] Etsuko Tokunaga,[a] and Norio Shibata*[a, b]
The direct synthesis of aryl triflones, that is, trifluoromethane-
sulfonyl arenes, was achieved through the trifluoromethanesul-
fonylation of benzynes. The trifluoromethanesulfonyl group,
one of the fluorinated functional groups, is a highly electron-
negative and mild lipophilic substituent. Aryl triflones have
high potential in the synthesis of bioactive compounds and
specialty materials. The treatment of 2-(trimethylsilyl)aryl tri-
fluoromethanesulfonates with cesium fluoride in the presence
of 15-crown-5 generated benzynes, which reacted with sodium
trifluoromethanesulfinate followed by protonation with tBuOH
under heating conditions, provided aryl triflones in moderated
to good yields. Both symmetrical and unsymmetrical triflones
were nicely accessed under the same reaction conditions. In-
terestingly, the trifluoromethanesulfonylation of unsymmetrical
benzyne precursors proceeded smoothly to furnish corre-
sponding aryl triflones in good yields with good to high regio-
selectivities. The balance of polarization of electric charge as
well as steric hindrance of the benzyne intermediates are cen-
tral factors to control the outcome of regioselectivity.
1. Introduction
Fluorinated aromatics are prevalent in specialty materials, phar-
maceuticals, and agrochemicals.[1] Aryl fluorides (ArÀF) and
benzotrifluorides (ArÀCF3) have served as two major contribu-
tors in the last half century. In recent years, arenes with heter-
oatom-linked trifluoromethyl modifications, such as trifluoro-
In fact, aryl triflones have been successfully used as central
structural motifs in biologically active molecules,[6] functional
materials,[7] and chiral catalysts.[8] The synthesis of aryl triflones
has been explored over the last two decades, leading to its
categorization into three methodologies: trifluoromethanesul-
methoxy arenes (ArÀOCF3),[2] trifluoromethylthio arenes (ArÀ fonylation of arenes,[5a,9] oxidation of aryl trifluoromethyl sul-
SCF3),[3] and trifluoromethanesulfonyl arenes (aryl triflones, ArÀ fides,[10] and trifluoromethylation of aryl sulfonyl fluorides or
SO2CF3)[3d,4–16] have been considerably targeted. Our group is
interested in aryl triflones.[3d,5] Aryl triflones have a functional
group, trifluoromethanesulfonyl (SO2CF3), which is a stronger
electron-withdrawing group than trifluoromethyl (CF3) (SO2CF3,
sm =0.79, sp =0.93; CF3, sm =0.43, sp =0.54), whereas its lipo-
philicity is milder than that of CF3 (SO2CF3, p=0.55; CF3, p=
0.88).[3d,17] Thus, the replacement of CF3–arene moieties in ex-
isting biologically active molecules and functional materials
with CF3SO2–arenes is a potential strategy to improve and/or
alter the stability and log P values of the original compounds.
aryl sulfonates.[11] From the viewpoint of late-stage functionali-
zation in pharmaceuticals, the direct trifluoromethanesulfonyla-
tion of arenes is particularly attractive.[12] In this context, we en-
visaged the use of benzynes for the direct synthesis of aryl tri-
flones. Benzynes have a strained triple bond, which is highly
reactive towards a wide variety of addition reactions.[18] We,
thus, started the investigation of the preparation of aryl tri-
flones using benzynes. During our investigation,[13] the only ex-
ample of the synthesis of trifluoromethanesulfonyl benzene
from benzyne was reported (Scheme 1a).[14] However, it fo-
cused exclusively on the phenylsulfonylation of benzynes, and
thus a general preparation of aryl triflones has not yet been es-
tablished. Later, Li and co-workers[15] and Zhao et al.,[16] in this
order, reported the synthesis of aryl triflones from benzynes
(Schemes 1b and 1c), but their methods were limited to the
preparation of ortho-substituted triflones. Finally, the direct
mono-functionalization of benzynes to triflones continues to
have limitations except for the single example by Singh and
co-workers.[14] Herein, we disclose a full account of our work
for the synthesis of aryl triflones through the trifluoromethane-
sulfonylation of benzynes (Scheme 1d).[13]
[a] Dr. Y. Sumii, Y. Sugita, E. Tokunaga, Prof. N. Shibata
Department of Nanopharmaceutical Sciences and
Department of Life Science and Applied Chemistry
Nagoya Institute of Technology
Gokiso-cho, Showa-ku, Nagoya 466–8555 (Japan)
E-mail: nozshiba@nitech.ac.jp
[b] Prof. N. Shibata
Institute of Advanced Fluorine-Containing Materials
Zhejiang Normal University
688 Yingbin Avenue, 321004 Jinhua (China)
Supporting Information and the ORCID identification number(s) for the
author(s) of this article can be found under https://doi.org/10.1002/
open.201700204.
A wide variety of aryl triflones can be nicely accessed in
moderated to good yields through the reaction of sodium tri-
fluoromethanesulfinate (NaSO2CF3; Langlois reagent)[19] with
benzynes followed by the addition of tBuOH for protonation.
Highly reactive benzyne derivatives were generated in situ
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This is an open access article under the terms of the Creative Commons
Attribution-NonCommercial License, which permits use, distribution and
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Table 1. Optimization of reaction conditions.[a]
Entry
F source
[equiv]
Additive
Temp.
[8C]
Time
[h]
Yield
[%]
1[b]
2
3
4
5
6
7
8
KF (4.0)
18-crown-6
-
-
-
-
15-crown-5
15-crown-5
15-crown-5
15-crown-5
15-crown-5
15-crown-5
15-crown-5
15-crown-5
RT
RT
RT
RT
RT
RT
RT
40
50
40
40
40
40
24
24
24
24
24
24
24
4
4
3
3
3
NR
15
9
trace
trace
19
44
45
42
42
CsF (4.0)
TMAF (4.0)
TBAF·3H2O (4.0)
TBAT(4.0)
CsF (4.0)
CsF (6.0)
CsF (6.0)
CsF (6.0)
CsF (6.0)
CsF (6.0)
CsF (6.0)
CsF (6.0)
Scheme 1. Synthesis of aryl triflones from benzynes: a) by Singh and co-
workers;[14] b) by Li and co-workers;[15] c) by Xu and co-workers;[16] d) this
work.
9
10[c]
11[d]
12[e]
13[f]
50
49
NR[g]
from 2-(trimethylsilyl)aryl trifluoromethanesulfonates with
cesium fluoride in the presence of 15-crown-5. This method is
useful not only for the synthesis of symmetrical aryl triflones,
but also unsymmetrical aryl triflones. More importantly, regio-
selective trifluoromethanesulfonylation of unsymmetrical ben-
zyne precursors was also achieved, depending on both the
steric hindrance and polarization of electric charge of ben-
zynes. An ionic pathway, rather than a radical pathway, for the
introduction of the SO2CF3 moiety to reactive benzynes was
suggested by the use of TEMPO (2,2,6,6-tetramethylpiperidine
1-oxyl) experiments. The regioselectivity observed was ana-
lyzed based on the computations.
3
[a] Reaction was carried out with 1a, NaSO2CF3 (2.0 equiv), an F source,
and an additive (2.0 equiv) in MeCN (1.0 mL). [b] KSO2CF3 was used in-
stead of NaSO2CF3, 18-crown-6 (6.0 equiv), with THF as the solvent.
[c] H2O (1.0 equiv) was added. [d] tBuOH (1.0 equiv) was added.
[e] TEMPO (2.0 equiv) was added. [f] Reaction was carried out using
NaSO2CH3 instead of NaSO2CF3. [g] No desired product, 2-methanesulfon-
yl naphthalene, was obtained.
pared by the oxidation of 2-trifluoromethylthio-naphthalene
(see the Supporting Information).
With the optimal reaction conditions in hand, we examined
the substrate scope for the trifluoromethanesulfonylation of
symmetrical benzynes derived from corresponding precursors,
2-(trimethylsilyl)phenyl trifluoromethanesulfonate derivatives
1a–e (Table 2). The simple benzyne generated from 1b provid-
ed the trifluoromethanesulfonyl benzene (2b) in a moderate
yield of 43% (entry 2). The alkyl-substituted benzyne derived
from 4,5-dimethyl-substituted 1c gave 2c in 63% yield. It
should be noted that the sterically demanding 3,6-dimethyl
benzyne precursor 1d was nicely converted to the dimethyl-
phenyl-triflone 2d in 76% yield (entry 4). The 5-trimethylsilyl-6-
trifluoromethanesulfonyloxy indane 1e also provided the cor-
responding 5-trifluoromethanesulfonylated indane 2e in 74%
yield (entry 5).
2. Results and Discussion
We first investigated the trifluoromethanesulfonylation of ben-
zynes by using 2-(trimethylsilyl)naphthalen-3-yl trifluorometha-
nesulfonate (1a) as a benzyne precursor. Under conventional
conditions[14,18] with KSO2CF3 (2.0 equiv)[20] and KF (4.0 equiv) in
tetrahydrofuran (THF) at room temperature, no desired trifluor-
omethanesulfonylated product 2a was observed (Table 1,
entry 1). We next attempted the reaction by using NaSO2CF3
and CsF in MeCN at room temperature. Desired 2a[5g,11 f] was
obtained in a low yield of 15% (entry 2). Screening the fluo-
rides did not improve this transformation (entries 3–5), where-
as the addition of 15-crown-5 increased the yield slightly to
19% (entry 6). The amount of CsF affected the conversion to
2a, increasing the yield to 44% (entry 7). Heating the reaction
shortened the reaction time without affecting significantly the
yield (entries 8, 9). We further examined the proton source.
The use of H2O was not effective (entry 10), but the addition of
1.0 equivalent of tBuOH improved the yield to 50% (entry 11).
The reaction was not inhibited in the presence of TEMPO, thus
an ionic reaction was suggested (entry 12). We also attempted
the reaction using sodium methanesulfinate (NaSO2CH3) in-
stead of NaSO2CF3, but no desired SO2CH3-containing product,
2-methanesulfonyl naphthalene, was obtained (entry 13). The
structure of product 2a was confirmed by spectroscopic analy-
sis [19F NMR d: À78.69 ppm (triflone, SO2CF3)] and also by a
comparison with an authentic sample of 2a, which was pre-
We next investigated the trifluoromethanesulfonylation of
unsymmetrical benzynes generated from 4- or 6-substituted
1-trimethylsilyl-2-trifluoromethanesulfonate
arenes
1 f–n
(Table 3). 4-Methyl benzyne precursor 1 f gave a mixture of aryl
triflones 2 f and 2 f’ in a 48:52 regioisomeric ratio in a com-
bined yield of 58% (entry 1). The bulky tBu-substituted ben-
zyne precursor 1g gave the corresponding regioisomeric aryl
triflones 2g and 2g’ in 47% yield in a ratio of 33:67 (entry 2).
4-Methoxy-substituted benzyne precursor 1h provided regioi-
someric products 2h and 2h’ in 57% yield (ratio, 74:26) selec-
tively (entry 3). High regioselectivities were observed by the re-
action of halogen-substituted benzyne precursors 1i and 1j to
furnish the aryl triflones 2i and 2i’ in 63% yield (ratio, 81:19)
and 2j and 2j’ in 41% yield (ratio, 85:15), respectively (en-
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Table 2. Trifluoromethanesulfonylation of symmetrical benzyne precur-
sors 1a–e.[a]
Table 3. Trifluoromethanesulfonylation of unsymmetrical benzyne precur-
sors 1 f–n.[a]
Entry
1
Substrate
Product
Yield [%]
50
Entry Substrate
1
Product
Yield[b] [%]
58
(48:52)
47
(33:67)
2
2
3
43
63
57
(74:26)
3
63
(81:19)
4
4
5
76
74
41
(85:15)
5
77
(48:52)
6[c]
[a] Reaction was carried out with 1, NaSO2CF3 (2.0 equiv), CsF (6.0 equiv),
15-crown-5 (2.0 equiv), and tBuOH (1.0 equiv) in MeCN (1.0 mL) at 408C
for 3 h.
64
(67:33)
7
8
9
42
(100:0)
tries 4 and 5). On the other hand, phenyl-substituted benzyne
precursor 1k gave the aryl triflones 2k and 2k’ in 77% yield in
a ratio of 48:52 at a higher reaction temperature (508C)
(entry 6). The unsymmetrical naphthalene-containing aryne
precursor 1l provided the trifluoromethanesulfonylated naph-
thalenes 2l (2a) and 2l’ (2a’) in 64% yield in a ratio of 67:33
(entry 7). It should be pointed out that 6-substituted 1-trime-
thylsilyl-2-trifluoromethanesulfonate benzyne precursors 1m
and 1n solely provided the 3-substituted phenyl triflones 2m’
(2h’) and 2n’ (2j’) in moderate yields, 42 and 27%, respective-
ly (entries 8 and 9).
27
(100:0)
[a] Reaction was carried out with 1a, NaSO2CF3 (2.0 equiv), CsF
(6.0 equiv), 15-crown-5 (2.0 equiv), tBuOH (1.0 equiv) in MeCN (1.0 mL) at
408C for 3 h. [b] The ratios of regioisomers are shown in parentheses and
were determined by crude products of 19F NMR spectroscopy. [c] Carried
out at 508C.
According to previous studies of regioselectivity of substitut-
ed benzynes,[14,21] the regioselectivity observed in Table 2 could
be rationally explained by both the balance of polarization of
the electric charge and steric hindrance of the benzyne inter-
mediates I (Scheme 2). Initially, Cs+ is captured by 15-crown-5
to generate naked fluoride anion, which attacks the silicon
atom of 1 to generate highly reactive benzynes I. Then, SO2CF3
anion attacks benzynes I followed by protonation with tBuOH
to provide desired aryl triflones 2 (Scheme 2). The formation of
the major meta-isomer 2g’ (R=tBu) can be explained by the
preferential attack of the SO2CF3 anion to C3, as C4 is more
negative because of the electron-donating effect of the tBu
substituent (positive inductive effect, Figure 1a).[21,22] On the
other hand, for the MeO-, Cl- and Br-substituted benzynes, the
major products are para-substituted regioisomers 2h, 2i, and
2j, indicating that the developing positive charge at the C4
position by the strong electron negativity of O(Me), Cl, and Br
(negative inductive effect) should be the main factor control-
ling regioselectivity (Figure 1b).[18h,21] In contrast, no selectivity
in the reaction of 1 f and 1k (R=Me, Ph) suggests that there is
no significant difference between steric and electronic factors
on C3 and C4 (Figure 1c).[22] Complete regioselective formation
of meta-substituted isomers 2m’ (2h’) and 2n’ (2j’) from 1m
and 1n should be explained by both the steric effect and po-
larization of the electric charge on C2 and C3 (Figure 1d).[21,22]
Scheme 2. Proposed reaction mechanism for the reaction of 1 to 2.
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experimental observations of the selectivity. In the case of 1-
tBu substitution of 3,4-benzyne, the electron density in the p
orbital at C3 (0.9103) was lower than that at C4 (0.9576) (Fig-
ure 2a). On the other hand, the electron densities in the p or-
bitals at C4 of 1-Cl- and Br-substituted 3,4-benzynes were
lower than those at C3 (Figure 2b). For 1-OMe-substituted 3,4-
benzyne, the direction of the Me group against the triple bond
strongly affected the bias of the electron density, and the elec-
tron densities in the cis-configuration of 1-OMe 3,4-benzyne
are in good agreement with the experimental observation,
whereas those of trans-configuration are not. In the case of
Me- and Ph-substituted 3,4-benzyne, the difference between
the electron densities are small, resulting in low regioselectivi-
ties (Figure 2c). Excellent regioselectivity was observed for
MeO- and Br-substituted 2,3-benzynes, which could be well ex-
plained based on the large difference of electron densities in
the p orbital at C3 and C2 (Figure 2d). The preferred formation
of 2-SO2CF3 naphthalene is also in good agreement with the
calculations (Figure 2e).
Figure 1. Proposed explanation of regioselectivity.
The preferred formation of 2-SO2CF3 naphthalene 2l (2a) is the
result of sterically favored attack on C2, owing to the steric re-
pulsion by peri-hydrogen in the 1,2-naphthalyne (Figure 1e).[22]
Finally, the regioselectivity was analyzed by computations.
The structures of benzynes were initially optimized by density
functional theory (DFT) [B3LYP/6-31G(d)],[23] and then the elec-
tron densities of their reacting p orbitals were calculated by
using a natural bond orbital (NBO) 6.0.[24,25] The differences of
the electron densities in the p orbital at the triple bond are
shown in Figure 2 and they are in good agreement with the
3. Conclusions
We have succeeded in synthesizing aryl triflones through the
direct trifluoromethanesulfonylation of benzynes. A wide varie-
ty of 1-trimethylsilyl-2-trifluoromethanesulfonate arenes are
feasible as precursors to generate highly reactive benzynes
upon treatment with CsF and 5-crown-15 followed by the re-
action with NaSO2CF3 to furnish a variety of aryl triflones in
moderate to good yields. Regioselective trifluoromethanesulfo-
nylation was achieved, depending on the substrate structures
and selectivity, by balancing the polarization of electric charge
and steric hindrance of the benzyne intermediates. All aryl tri-
flones are expected to serve as building blocks for biologically
active molecules and materials. As excess amounts of the re-
agents are necessary in the present method, further improve-
ment of the reaction conditions are required. Applications of
this methodology, including the synthesis of heteroaryl tri-
flones,[4] are also under investigation.
Experimental Section
General Procedure of Trifluoromethanesulfonylation
To a stirred solution of 2-(trimethylsilyl)aryl trifluoromethanesulfo-
nates 1[26] (0.1 mmol), sodium trifluoromethanesulfinate (31.2 mg,
0.2 mmol, 2.0 equiv) in acetonitrile (1.0 mL) was added with 15-
crown-5 (39.7 mL, 0.2 mmol, 2.0 equiv), tert-butyl alcohol (9.5 mL,
0.1 mmol, 1.0 equiv), and cesium fluoride (91.2 mg, 0.6 mmol,
6.0 equiv) at room temperature under a nitrogen atmosphere.
After the reaction mixture was stirred at 408C for 3 h, it was
cooled to room temperature, water was added, and the whole mix-
ture was extracted with Et2O. The combined organic layers were
washed with brine, dried over Na2SO4, and concentrated under re-
duced pressure to give the crude product. The residue was purified
by column chromatography (n-hexane/ethyl acetate=95/5) on
silica gel to give trifluoromethanesulfonyl benzenes 2.
Figure 2. NBO analysis of substituted benzynes. Optimized structures of ben-
zynes were calculated by using DFT [B3LYP6/31G(d)]. The electron densities
of the reacting p orbitals were determined by NBO analysis. The arrow indi-
cates the preferred direction of selectivity.
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2-(Trifluoromethylsulfonyl)naphthalene (2a)[5g,11f]
1,4-Dimethyl-2-(trifluoromethylsulfonyl)benzene (2d)
A reaction of 2-(trimethylsilyl)naphthalen-3-yl trifluoromethanesul-
fonate 1a (34.8 mg, 0.1 mmol), sodium trifluoromethanesulfinate
(31.2 mg, 0.2 mmol, 2.0 equiv), 15-crown-5 (39.7 mL, 0.2 mmol,
2.0 equiv), tert-butyl alcohol (9.5 mL, 0.1 mmol, 1.0 equiv), and
cesium fluoride (91.2 mg, 0.6 mmol, 6.0 equiv) in acetonitrile
(1.0 mL) proceeded at 408C for 3 h. Subsequent purification by
column chromatography (n-hexane/ethyl acetate=95/5) on silica
gel gave 2-(trifluoromethylsulfonyl)naphthalene 2a (13.1 mg, 50%)
as a yellow solid.
A reaction of 3,6-dimethyl-2-(trimethylsilyl)phenyl trifluorometha-
nesulfonate 1d (32.6 mg, 0.1 mmol), sodium trifluoromethanesulfi-
nate (31.2 mg, 0.2 mmol, 2.0 equiv), 15-crown-5 (39.7 mL, 0.2 mmol,
2.0 equiv), tert-butyl alcohol (9.5 mL, 0.1 mmol, 1.0 equiv), and
cesium fluoride (91.2 mg, 0.6 mmol, 6.0 equiv) in acetonitrile
(1.0 mL) proceeded at 408C for 3 h. Subsequent purification by
column chromatography (n-hexane/ethyl acetate=95/5) on silica
gel gave 1,4-dimethyl-2-(trifluoromethylsulfonyl)benzene 2d
(18.0 mg, 76%) as a colorless oil.
1
1
2a: H NMR (CDCl3, 300 MHz) d: 7.69–7.81 (m, 2H), 7.94–8.01 (m,
2d: H NMR (CDCl3, 300 MHz) d: 2.43 (s, 3H), 2.68 (s, 3H), 7.32 (d,
2H), 8.06–8.11 (m, 2H), 8.67 (s, 1H) ppm; 19F NMR (CDCl3, 282 MHz)
d: À78.7 (s, 3F) ppm; 13C NMR (CDCl3, 150.9 MHz) d: 119.9 (q, J=
325.9 Hz), 123.7, 128.0, 128.1, 128.3, 129.8, 130.2, 130.8, 132.0,
134.0 (m), 136.5 ppm; IR (KBr): 3422, 3057, 2928, 2367, 1922, 1822,
1736, 1624, 1588, 1503, 1454, 1363, 1271, 1213, 1124, 1064, 1019,
J=7.5 Hz, 1H), 7.48 (d, J=7.5 Hz, 1H) 7.88 (s, 1H) ppm; 19F NMR
(CDCl3, 282 MHz) d: À78.8 (s, 3F) ppm; 13C NMR (CDCl3, 150.9 MHz)
d: 20.1, 20.6, 120.1 (q, J=326.4 Hz), 129.3, 133.3, 133.5, 137.2,
137.4, 139.0 ppm; IR (NaCl): 2932, 2372, 2351, 2326, 1653, 1558,
1495, 1456, 1393, 1361, 1283, 1215, 1125, 1059, 885, 826, 764, 701,
955, 911, 857, 812, 746, 664, 578, 469 cmÀ1; mp (CHCl3): 61.0– 615, 588, 530, 481, 425, 412 cmÀ1; MS (EI, m/z): 238 (M+); HRMS
62.08C; MS (EI, m/z): 260 (M+); HRMS (EI): calcd for C11H7F3O2S:
(EI): calcd for C9H9F3O2S: 238.0275, found: 238.0298.
260.0119, found: 260.0135.
2,3-Dihydro-5-(trifluoromethylsulfonyl)-1H-indene (2e)
A reaction of 2,3-dihydro-5-(trimethylsilyl)-1H-inden-6-yl trifluoro-
methanesulfonate 1e (33.8 mg, 0.1 mmol), sodium trifluorometha-
nesulfinate (31.2 mg, 0.2 mmol, 2.0 equiv), 15-crown-5 (39.7 mL,
0.2 mmol, 2.0 equiv), tert-butyl alcohol (9.5 mL, 0.1 mmol, 1.0 equiv),
and cesium fluoride (91.2 mg, 0.6 mmol, 6.0 equiv) in acetonitrile
(1.0 mL) proceeded at 408C for 3 h. Subsequent purification by
column chromatography (n-hexane/ethyl acetate=95/5) on silica
gel gave 2,3-dihydro-5-(trifluoromethylsulfonyl)-1H-indene 2e
(18.5 mg, 50%) as a white solid.
1-(Trifluoromethylsulfonyl)benzene (2b)[11f,27]
A reaction of 2-(trimethylsilyl)phenyl trifluoromethanesulfonate 1b
(29.8 mg, 0.1 mmol), sodium trifluoromethanesulfinate (31.2 mg,
0.2 mmol, 2.0 equiv), 15-crown-5 (39.7 mL, 0.2 mmol, 2.0 equiv),
tert-butyl alcohol (9.5 mL, 0.1 mmol, 1.0 equiv), and cesium fluoride
(91.2 mg, 0.6 mmol, 6.0 equiv) in acetonitrile (1.0 mL) proceeded at
408C for 3 h. Subsequent purification by column chromatography
(n-hexane/ethyl acetate=95/5) on silica gel gave 1-(trifluorome-
thylsulfonyl)benzene 2b (9.0 mg, 43%) as a colorless oil.
1
2e: H NMR (CDCl3, 300 MHz) d: 2.14–2.24 (m, 2H), 3.02–3.07 (m,
1
4H), 7.49 (d, J=7.8 Hz, 1H), 7.82 (d, J=7.8 Hz, 1H), 7.85 (s, 1H)
ppm; 19F NMR (CDCl3, 282 MHz) d: À79.1 (s, 3F) ppm; 13C NMR
(CDCl3, 150.9 MHz) d: 25.2, 32.5, 33.2, 119.9 (q, J=325.9 Hz), 125.6,
126.4, 128.7, 129.2, 146.5, 154.8 ppm; IR (KBr): 3066, 2969, 1931,
1814, 1598, 1573, 1437, 1413, 1363, 1216, 1063, 886, 828, 763, 686,
607, 518, 460, 417 cmÀ1; mp: 58.0–59.08C (CHCl3); MS (EI, m/z): 250
(M+); HRMS (EI): calcd for C10H9F3O2S: 250.0275, found: 250.0302.
2b: H NMR (CDCl3, 300 MHz) d: 7.67–7.72 (m, 2H), 7.83–7.88 (m,
1H), 8.06 (d, J=8.1 Hz, 2H) ppm; 19F NMR (CDCl3, 282 MHz) d:
À78.9 (s, 3F) ppm; 13C NMR (CDCl3, 150.9 MHz) d: 119.8 (q, J=
325.9 Hz), 129.9, 130.8, 131.3, 136.6 ppm; IR (NaCl): 2360, 1844,
1793, 1771, 1734, 1716, 1699, 1684, 1653, 1635, 1616, 1576, 1558,
1541, 1521, 1507, 1473, 1456, 1437, 1418, 1373, 1074 cmÀ1; MS (EI,
m/z): 141 (M-CF3+); HRMS (EI): calcd for C6H5O2S: 141.0010, found:
141.0055.
1-Methyl-4-(trifluoromethylsulfonyl)benzene (2 f)[28] and
1-Methyl-3-(trifluoromethylsulfonyl)benzene (2 f’)[28]
1,2-Dimethyl-4-(trifluoromethylsulfonyl)benzene (2c)
A reaction of 4-methyl-2-(trimethylsilyl)phenyl trifluoromethanesul-
fonate 1 f (31.2 mg, 0.1 mmol), sodium trifluoromethanesulfinate
(31.2 mg, 0.2 mmol, 2.0 equiv), 15-crown-5 (39.7 mL, 0.2 mmol,
2.0 equiv), tert-butyl alcohol (9.5 mL, 0.1 mmol, 1.0 equiv), and
cesium fluoride (91.2 mg, 0.6 mmol, 6.0 equiv) in acetonitrile
(1.0 mL) proceeded at 408C for 3 h. Subsequent purification by
column chromatography (n-hexane/ethyl acetate=95/5) on silica
gel gave inseparable mixture of 1-methyl-4-(trifluoromethylsulfo-
nyl)benzene 2 f and 1-methyl-3-(trifluoromethylsulfonyl)benzene
2 f’(12.8 mg, 57%, 48:52) as a colorless oil.
A reaction of 4,5-dimethyl-2-(trimethylsilyl)phenyl trifluorometha-
nesulfonate 1c (32.6 mg, 0.1 mmol), sodium trifluoromethanesulfi-
nate (31.2 mg, 0.2 mmol, 2.0 equiv), 15-crown-5 (39.7 mL, 0.2 mmol,
2.0 equiv), tert-butyl alcohol (9.5 mL, 0.1 mmol, 1.0 equiv), and
cesium fluoride (91.2 mg, 0.6 mmol, 6.0 equiv) in acetonitrile
(1.0 mL) proceeded at 408C for 3 h. Subsequent purification by
column chromatography (n-hexane/ethyl acetate=95/5) on silica
gel gave 1,2-dimethyl-4-(trifluoromethylsulfonyl)benzene 2c
(15.1 mg, 63%) as a white solid.
1
2c: H NMR (CDCl3, 300 MHz) d: 2.39 (s, 3H), 2.41 (s, 3H), 7.42 (d,
Mixture of 2 f and 2 f’: 1H NMR (CDCl3, 300 MHz) d: 2.50 (s, 3H),
2.52 (s, 3H), 7.47 (d, J=7.8 Hz, 2H), 7.53–7.58 (m, 1H), 7.63–7.65
(m, 1H), 7.82–7.86 (m, 2H), 7.93 (d, J=8.4 Hz, 2H) ppm; 19F NMR
(CDCl3, 282 MHz) d: À79.1(minor, s, 3F, 2 f), À79.0 (major, s, 3F, 2 f’)
ppm; 13C NMR (CDCl3, 150.9 MHz) d: 21.2, 21.9, 119.77 (q, J=
325.9 Hz), 119.80 (q, J=325.9 Hz), 127.9, 128.1, 129.7, 130.5, 130.7,
130.8, 131.1, 137.4, 140.4, 148.4 ppm; IR (NaCl): 3070, 2930, 2372,
2322, 1596, 1477, 1365, 1310, 1210, 1140, 1078, 866, 816, 791, 763,
J=7.5 Hz, 1H), 7.76–7.78 (m, 2H) ppm; 19F NMR (CDCl3, 282 MHz)
d: À79.2 (s, 3F) ppm; 13C NMR (CDCl3, 150.9 MHz) d: 19.8, 20.3,
119.8 (q, J=325.9 Hz), 128.1, 128.3, 131.0, 131.2, 139.0, 147.1 ppm;
IR (KBr): 3083, 2952, 2877, 2609, 2375, 1930, 1790, 1654, 1596,
1483, 1451, 1362, 1304, 1216, 1125, 1082, 1024, 893, 826, 763, 705,
672, 608, 509 cmÀ1; mp (CHCl3): 50.5–51.58C; MS (EI, m/z): 238 (M+
); HRMS (EI): calcd for C9H9F3O2S: 238.0275, found: 238.0296.
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698, 683, 664, 613, 590, 561, 530, 518 cmÀ1; MS (EI, m/z): 224 (M+);
HRMS (EI): calcd for C8H7F3O2S: 224.0119, found: 224.0134.
(CDCl3, 282 MHz) d: À78.8 (s, 3F) ppm; 13C NMR (CDCl3, 150.9 MHz)
d: 55.9, 114.6, 119.8 (q, J=325.9 Hz), 122.9, 123.2, 130.9, 132.3,
160.4 ppm; IR (NaCl): 3084, 3016, 2946, 2844, 1732, 1600, 1483,
1436, 1368, 1329, 1292, 1249, 1216, 1134, 1089, 1072, 1038, 857,
790, 763, 695, 623, 587, 469 cmÀ1; MS (EI, m/z): 240 (M+); HRMS
(EI): calcd for C8H7F3O3S: 240.0068, found: 240.0089.
1-tertButyl-4-(trifluoromethylsulfonyl)benzene (2g)[11f,5g] and
1-tertButyl-3-(trifluoromethylsulfonyl)benzene (2g’)
A reaction of 4-tert-butyl-2-(trimethylsilyl)phenyl trifluoromethane-
sulfonate 1k (35.4 mg, 0.1 mmol), sodium trifluoromethanesulfi-
nate (31.2 mg, 0.2 mmol, 2.0 equiv), 15-crown-5 (39.7 mL, 0.2 mmol,
2.0 equiv), tert-butyl alcohol (9.5 mL, 0.1 mmol, 1.0 equiv), and
cesium fluoride (91.2 mg, 0.6 mmol, 6.0 equiv) in acetonitrile
(1.0 mL) proceeded at 408C for 3 h. Subsequent purification by
column chromatography (n-hexane/ethyl acetate=95/5) on silica
gel gave a mixture of 1-tert-butyl-4-(trifluoromethylsulfonyl)ben-
zene 2g and 1-tert-butyl-3-(trifluoromethylsulfonyl)benzene 2g’
(16.1 mg, 77%, 33:67) as a colorless oil.
1-Chloro-4-(trifluoromethylsulfonyl)benzene (2i)[5g,28] and
1-Chloro-3-(trifluoromethylsulfonyl)benzene (2i’)[28]
A reaction of 4-chloro-2-(trimethylsilyl)phenyl trifluoromethanesul-
fonate 1i (33.3 mg, 0.1 mmol), sodium trifluoromethanesulfinate
(31.2 mg, 0.2 mmol, 2.0 equiv), 15-crown-5 (39.7 mL, 0.2 mmol,
2.0 equiv), tert-butyl alcohol (9.5 mL, 0.1 mmol, 1.0 equiv), and
cesium fluoride (91.2 mg, 0.6 mmol, 6.0 equiv) in acetonitrile
(1.0 mL) proceeded at 408C for 3 h. Subsequent purification by
column chromatography (n-hexane/ethyl acetate=95/5) on silica
gel gave a mixture of 1-chloro-4-(trifluoromethylsulfonyl)benzene
2i and 1-chloro-3-(trifluoromethylsulfonyl)benzene 2i’ (10.0 mg,
41%, 81:19) as a white semisolid.
1
Mixture of 2g and 2g’: H NMR (CDCl3, 300 MHz) d: 1.38 (s, 9H),
7.60 (t, J=8.0 Hz, 0.66H), 7.74 (d, J=8.7 Hz, 0.66H), 7.87 (d, J=
7.8 Hz, 1.33H), 7.94 (d, J=8.4 Hz, 0.66H), 8.02 (s, 0.66H) ppm;
19F NMR (CDCl3, 282 MHz) d: À79.1 (minor, s, 3F, 2g), À79.0 (major,
s, 3F, 2g’) ppm; 13C NMR (CDCl3, 150.9 MHz) d: 30.8, 30.9, 35.2,
35.6, 119.79 (q, J=325.9 Hz), 119.82 (q, J=325.4 Hz), 127.0, 127.4,
127.9, 128.0, 129.6, 130.6, 130.9, 133.9, 153.7, 161.2 ppm; IR (NaCl):
2968, 2309, 1593, 1482, 1368, 1217, 1146, 1079, 840, 781, 692, 678,
631, 591, 497, 467, 457, 439 cmÀ1; MS (EI, m/z): 266 (M+), HRMS
(EI): calcd for C11H13F3O2S: 266.0588, found: 266.0631.
1
2i: White solid. H NMR (CDCl3, 300 MHz) d: 7.67 (d, J=6.9 Hz, 2H),
7.99 (d, J=7.2 Hz, 2H) ppm; 19F NMR (CDCl3, 282 MHz) d: À78.8 (s,
3F) ppm; 13C NMR (CDCl3, 150.9 MHz) d: 119.6 (q, J=325.4 Hz),
129.7, 130.4, 132.1, 144.0 ppm; IR (KBr): 3421, 3099, 2963, 2367,
1719, 1580, 1475, 1397, 1373, 1327, 1261, 1220, 1142, 1092, 1073,
1014, 804, 770, 702, 631, 580, 472 cmÀ1; mp: 49.0–50.08C (CHCl3);
MS (EI, m/z): 111 (M-SO2CF3+), HRMS (EI): calcd for C6H4Cl: 111.0002,
found: 110.9991.
1-Methoxy-4-(trifluoromethylsulfonyl)benzene (2h)[11f,27,28]
and 1-Methoxy-3-(trifluoromethylsulfonyl)benzene (2h’
(2m’))
2i’: Colorless oil. 1H NMR (CDCl3, 300 MHz) d: 7.64 (t, J=8.0 Hz,
1H), 7.82 (d, J=8.1 Hz, 1H), 7.95 (d, J=8.1 Hz, 1H), 8.03 (s, 1H)
ppm; 19F NMR (CDCl3, 282 MHz) d: À78.5 (s, 3F) ppm; 13C NMR
(CDCl3, 150.9 MHz) d: 119.6 (q, J=325.9 Hz), 128.9, 130.6, 131.1,
133.1, 136.4, 136.8 ppm; IR (NaCl): 3075, 2920, 2850, 2352, 1725,
1578, 1462, 1411, 1373, 1305, 1215, 1146, 1103, 1074, 889, 793, 760,
Synthesis from 1h: A reaction of 4-methoxy-2-(trimethylsilyl)phenyl
trifluoromethanesulfonate 1h (32.8 mg, 0.1 mmol), sodium trifluor-
omethanesulfinate (31.2 mg, 0.2 mmol, 2.0 equiv), 15-crown-5
(39.7 mL, 0.2 mmol, 2.0 equiv), tert-butyl alcohol (9.5 mL, 0.1 mmol,
1.0 equiv), and cesium fluoride (91.2 mg, 0.6 mmol, 6.0 equiv) in
acetonitrile (1.0 mL) proceeded at 408C for 3 h. Subsequent purifi-
cation by column chromatography (n-hexane/ethyl acetate=95/5)
on silica gel gave 1-methoxy-4-(trifluoromethylsulfonyl)benzene 2h
and 1-methoxy-3-(trifluoromethylsulfonyl)benzene 2h’ (15.1 mg,
63%, 74:26) as a colorless oil.
672, 612, 582, 534, 521, 499, 488 cmÀ1; MS (EI, m/z): 111 (M-SO2CF3
), HRMS (EI): calcd for C6H4Cl: 111.0002 Found: 111.0009.
+
1-Bromo-4-(trifluoromethylsulfonyl)benzene (2j)[5g,27,28] and
1-Bromo-3-(trifluoromethylsulfonyl)benzene (2j’ (2n’))[5g]
Synthesis from 1m: A reaction of 6-methoxy-2-(trimethylsilyl)phen-
yl trifluoromethanesulfonate 1m (32.8 mg, 0.1 mmol), sodium tri-
fluoromethanesulfinate (31.2 mg, 0.2 mmol, 2.0 equiv), 15-crown-5
(39.7 mL, 0.2 mmol, 2.0 equiv), tert-butyl alcohol (9.5 mL, 0.1 mmol,
1.0 equiv), and cesium fluoride (91.2 mg, 0.6 mmol, 6.0 equiv) in
acetonitrile (1.0 mL) proceeded at 408C for 3 h. Subsequent purifi-
cation by column chromatography (n-hexane/ethyl acetate=95/5)
on silica gel gave 1-methoxy-3-(trifluoromethylsulfonyl)benzene
2m’ (2h’) (10.0 mg, 42%) as a colorless oil.
Synthesis from 1j: A reaction of 4-bromo-2-(trimethylsilyl)phenyl
trifluoromethanesulfonate 1j (37.7 mg, 0.1 mmol), sodium trifluoro-
methanesulfinate (31.2 mg, 0.2 mmol, 2.0 equiv), 15-crown-5
(39.7 mL, 0.2 mmol, 2.0 equiv), tert-butyl alcohol (9.5 mL, 0.1 mmol,
1.0 equiv), and cesium fluoride (91.2 mg, 0.6 mmol, 6.0 equiv) in
acetonitrile (1.0 mL) proceeded at 408C for 3 h. Subsequent purifi-
cation by column chromatography (n-hexane/ethyl acetate=95/5)
on silica gel gave 1-bromo-4-(trifluoromethylsulfonyl)benzene 2j
and 1-bromo-3-(trifluoromethylsulfonyl)benzene 2j’ (13.5 mg, 47%,
85:15) as a white semisolid.
1
2h: Colorless oil. H NMR (CDCl3, 300 MHz) d: 3.94 (s, 3H), 7.11 (d,
J=9.0 Hz, 2H), 7.97 (d, J=9.3 Hz, 2H) ppm; 19F NMR (CDCl3,
282 MHz) d: À79.4 (s, 3F) ppm; 13C NMR (CDCl3, 150.9 MHz) d: 55.9,
115.2, 119.8 (q, J=325.4 Hz), 121.7, 133.1, 166.2 ppm; IR (NaCl):
3103, 2951, 2847, 2593, 2345, 1594, 1577, 1498, 1464, 1442, 1362,
1318, 1275, 1216, 1191, 1141, 1075, 1022, 837, 805, 805, 763, 673,
590 cmÀ1; MS (EI, m/z): 240 (M+); HRMS (EI) calcd for C8H7F3O3S:
240.0068, found: 240.0093.
Synthesis from 1n: A reaction of 6-bromo-2-(trimethylsilyl)phenyl
trifluoromethanesulfonate 1n (37.7 mg, 0.1 mmol), sodium trifluor-
omethanesulfinate (31.2 mg, 0.2 mmol, 2.0 equiv), 15-crown
5
(39.7 mL, 0.2 mmol, 2.0 equiv), tert-butyl alcohol (9.5 mL, 0.1 mmol,
1.0 equiv), and cesium fluoride (91.2 mg, 0.6 mmol, 6.0 equiv) ace-
tonitrile (1.0 mL) proceeded at 408C for 3 h. Subsequent purifica-
tion by column chromatography (n-hexane/ethyl acetate=95/5)
on silica gel gave 1-bromo-3-(trifluoromethylsulfonyl)benzene 2n’
(2j’) (7.9 mg, 27%) as a white solid.
1
2h’: Colorless oil. H NMR (CDCl3, 300 MHz) d: 3.91 (s, 3H), 7.35 (d,
J=8.1 Hz, 1H), 7.50 (s, 1H), 7.55–7.66 (m, 2H) ppm; 19F NMR
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ꢀ 2018 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

1
1
2j: White solid. H NMR (CDCl3, 300 MHz) d: 7.83 (d, J=8.4 Hz, 2H),
Mixture of 2l (2a) and 2l’ (2a’): H NMR (CDCl3, 300 MHz) d: 7.67–
7.90 (d, J=8.7 Hz, 2H) ppm; 19F NMR (CDCl3, 282 MHz) d: À78.8 (s,
3F) ppm; 13C NMR (CDCl3, 150.9 MHz) d: 119.6 (q, J=325.9 Hz),
130.2, 132.0, 132.8, 133.4 ppm; IR (KBr): 3098, 2957, 2562, 2370,
2344, 1719, 1573, 1469, 1373, 1218, 1139, 1070, 1011, 826, 767,
699, 617, 578, 524, 474, 418 cmÀ1; mp: 63.5–64.58C (CHCl3); MS (EI,
m/z): 219 (M-CF3+), HRMS (EI): calcd for C6H4BrO2S: 218.9115,
found: 218.9143.
7.82 (m, 2.32H), 7.94–8.01 (m, 1.33H), 8.06–8.11 (m, 1.66H), 8.31 (d,
J=8.4 Hz, 0.33H), 8.47 (d, J=7.8 Hz, 0.33H), 8.67 (s, 0.66H), 8.82 (d,
J=9 Hz, 0.33H) ppm; 19F NMR (CDCl3, 282 MHz) d: À78.7 (major, s,
3F, 2l (2a)), À78.3 (minor, s, 3F, 2l’ (2a’)) ppm; 13C NMR (CDCl3,
150.9 MHz) d: 119.9 (q, J=325.9 Hz), 120.2 (q, J=327.0 Hz), 123.6,
124.3, 124.4, 126.7, 127.7, 127.9, 128.1, 128.3, 129.2, 129.6, 129.8,
130.0, 130.1, 130.8, 132.0, 134.0 (m), 134.2, 135.1, 136.5, 138.4 ppm
IR (KBr): 3057, 2963, 2318, 1717, 1624, 1588, 1506, 1456, 1362,
1261, 1213, 1114, 1065, 1020, 972, 857, 812, 747, 663, 578, 513,
470 cmÀ1; MS (EI, m/z): 260 (M+); HRMS (EI): calcd for C11H7F3O2S:
260.0119, found: 260.0133.
2j’: Colorless oil; 1H NMR (CDCl3, 300 MHz) d:7.55–7.61 (m, 1H),
7.97–8.00 (m, 2H), 8.19 (s, 1H) ppm; 19F NMR (CDCl3, 282 MHz) d:
À78.5 (s, 3F) ppm; 13C NMR (CDCl3, 150.9 MHz) d: 119.6 (q, J=
325.9 Hz), 123.9, 129.3, 131.3, 133.2, 133.4, 139.7 ppm; IR (NaCl):
3088, 2929, 2352, 1717, 1572, 1460, 1406, 1373, 1302, 1215, 1145,
1073, 782, 674, 658, 610, 580, 523, 498, 480, 452, 436, 425,
407 cmÀ1; MS (EI, m/z): 288 (M+), HRMS (EI): calcd for C7H4BrF3O2S:
287.9067, found: 287.9132.
Acknowledgements
This research is partially supported by JSPS KAKENHI Grant
Number JP 16H01142 in Middle Molecular Strategy, Advanced
Catalytic Transformation (ACT-C, JPMJCR12Z7) from the JST
Agency, JSPS KAKENHI Grant Number JP16H01017 in Precisely De-
signed Catalysts with Customized Scaffolding and the Pesticide
Science Society of Japan (ET). We thank Mr. Kanji Iwamoto for
his contribution in the early stage of this work. NaSO2CF3 was a
gift from Central Glass Co., Ltd.
4-(Trifluoromethylsulfonyl)biphenyl (2k) [5g,11f] and 3-(Tri-
fluoromethylsulfonyl)biphenyl (2k’)
A reaction of 4-phenyl-2-(trimethylsilyl)phenyl trifluoromethanesul-
fonate 1k (29.8 mg, 0.1 mmol), sodium trifluoromethanesulfinate
(31.2 mg, 0.2 mmol, 2.0 equiv), 15-crown-5 (39.7 mL, 0.2 mmol,
2.0 equiv), tert-butyl alcohol (9.5 mL, 0.1 mmol, 1.0 equiv), and
cesium fluoride (91.2 mg, 0.6 mmol, 6.0 equiv) in acetonitrile
(1.0 mL) proceeded at 508C for 3 h. Subsequent purification by
column chromatography (n-hexane/ethyl acetate=95/5) on silica
gel gave 4-(trifluoromethylsulfonyl)biphenyl 2k and 3-(trifluorome-
thylsulfonyl)biphenyl 2k’ (18.3 mg, 64%, 48:52) as a white solid.
Conflict of Interest
The authors declare no conflict of interest.
2k: White solid. 1H NMR (CDCl3, 300 MHz) d: 7.45–7.54 (m, 3H),
7.62–7.65 (m, 2H), 7.86 (d, J=7.8 Hz, 2H), 8.09 (d, J=8.4 Hz, 2H)
ppm; 19F NMR (CDCl3, 282 MHz) d: À78.9 (s, 3F) ppm; 13C NMR
(CDCl3, 150.9 MHz) d: 119.8 (q, J=325.4 Hz), 127.5, 128.4, 129.25,
129.33, 129.5, 131.3, 138.4, 149.6 ppm; IR (KBr): 3071, 2567, 2347,
1937, 1814, 1686, 1593, 1561, 1479, 1449, 1401, 1359, 1318, 1293,
1212, 1139, 1071, 1005, 847, 767, 677, 608, 580, 526 cmÀ1; mp
(CHCl3): 76.5–77.58C; MS (EI, m/z): 286 (M+), HRMS (EI): calcd for
C13H9F3O2S: 286.0275, found: 286.0271.
Keywords: benzynes · fluorine · pharmaceuticals
trifluoromethanesulfonyl group · trifluoromethanesulfonylation
·
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2k’: Colorless oil. 1H NMR (CDCl3, 300 MHz) d: 7.43–7.53 (m, 3H),
7.60–7.62 (m, 2H), 7.71–7.76 (m, 1H), 8.00–8.05 (m, 2H), 8.23 (s,
1H) ppm; 19F NMR (CDCl3, 282 MHz) d: À78.8 (s, 3F) ppm; 13C NMR
(CDCl3, 150.9 MHz) d: 119.8 (q, J=325.9 Hz), 127.2, 128.8, 129.0,
129.2, 129.3, 130.3, 131.9, 135.1, 138.2, 143.4 ppm; IR (NaCl): 3068,
3035, 1595, 1471, 1453, 1411, 1367, 1311, 1283, 1216, 1138, 1080,
1047, 1022, 994, 901, 811, 756, 698, 627, 587, 548, 523 cmÀ1; MS (EI,
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286.0255.
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2-(Trifluoromethylsulfonyl)naphthalene (2l (2a)) and 1-(Tri-
fluoromethylsulfonyl)naphthalene (2l’ (2a’))[5g]
A reaction of 1-(trimethylsilyl)naphthalen-2-yl trifluoromethanesul-
fonate 1l (34.8 mg, 0.1 mmol), sodium trifluoromethanesulfinate
(31.2 mg, 0.2 mmol, 2.0 equiv), 15-crown-5 (39.7 mL, 0.2 mmol,
2.0 equiv), tert-butyl alcohol (9.5 mL, 0.1 mmol, 1.0 equiv), and
cesium fluoride (91.2 mg, 0.6 mmol, 6.0 equiv) in acetonitrile
(1.0 mL) proceed at 408C for 3 h. Subsequent purification by
column chromatography (n-hexane/ethyl acetate=95/5) on silica
gel gave inseparable mixture of 2-(trifluoromethylsulfonyl)naphtha-
lene 2l (2a) and 1-(trifluoromethylsulfonyl)naphthalene 2l’ (2a’)
(15.8 mg, 58%, 67:33) as a yellow semisolid.
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Received: December 28, 2017
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