Mono- and dinitration of pentafluorosulfanylbenzenes with [NO 2][BF4], and substrate selectivity (PhSF5 vs PhCF3 and PhSF5 vs PhNO2) in competitive nitration

Article abstract of DOI:10.1016/j.jfluchem.2014.06.024

PhSF₅ 1 reacts with NO₂⁺BF ₄^-/TfOH in CH₂Cl₂ (DCM) at room temperature to give 1-nitro-3-(pentafluorosulfanyl)benzene 2 in near quantitative yield. The dinitro derivative 4 is synthesized from 2 by reaction with NO₂⁺BF₄^-/TfOH at 70 °C. The p-MeC₆H₄SF₅ is mononitrated at room temperature with NO₂⁺BF₄^-/DCM and dinitrated with NO₂⁺BF₄^-/TfOH. Substrate selectivity (kPhSF₅^kRPh) in competitive nitration for PhSF₅/PhCF₃ and PhSF₅/PhNO ₂ with NO₂⁺BF₄^- in DCM at room temperature was determined at 21.3 and ～1 respectively. Relative stability of the corresponding benzenium ions were gauged by DFT from the isodesmic proton transfer reaction SF₅-C₆H ₆⁺ + R-C₆H₅ → SF ₅-C₆H₅ + R-C₆H₆ ⁺ (R = CF₃ and NO₂). These studies indicate that reactivity of ArSF₅ in S_EAr is similar to ArNO ₂.

Full text of DOI:10.1016/j.jfluchem.2014.06.024

Journal of Fluorine Chemistry 165 (2014) 96–100
Contents lists available at ScienceDirect
Journal of Fluorine Chemistry
journal homepage: www.elsevier.com/locate/fluor
Mono- and dinitration of pentafluorosulfanylbenzenes with
[NO2][BF4], and substrate selectivity (PhSF5 vs PhCF3 and PhSF5
vs PhNO2) in competitive nitration
Takao Okazaki a,b, Kenneth K. Laali a,
*
a Department of Chemistry, University of North Florida, 1 UNF Drive, Jacksonville, FL 32224, USA
b Department of Chemistry for Materials, Graduate School of Engineering, Mie University, Tsu 514-8507, Japan
A R T I C L E I N F O
A B S T R A C T
PhSF5
reacts with NO2+BF4ꢀ/TfOH in CH2Cl2 (DCM) at room temperature to give 1-nitro-3-
Article history:
1
Received 21 May 2014
Received in revised form 19 June 2014
Accepted 24 June 2014
Available online 2 July 2014
(pentafluorosulfanyl)benzene 2 in near quantitative yield. The dinitro derivative 4 is synthesized from 2
by reaction with NO2+BF4ꢀ/TfOH at 70 8C. The p-MeC6H4SF5 is mononitrated at room temperature with
NO2+BF4ꢀ/DCM and dinitrated with NO2+BF4ꢀ/TfOH. Substrate selectivity (kPhSF =kRPh) in competitive
5
nitration for PhSF5/PhCF3 and PhSF5/PhNO2 with NO2+BF4ꢀ in DCM at room temperature was determined
at 21.3 and ꢁ1 respectively. Relative stability of the corresponding benzenium ions were gauged by DFT
Keywords:
+
from the isodesmic proton transfer reaction SF5–C6H6+ + R-C6H5 ! SF5–C6H5 + R-C6H6 (R = CF3 and
SF5-aromatics
NO2). These studies indicate that reactivity of ArSF5 in SEAr is similar to ArNO2.
Mono- and dinitration
NO2+BF4ꢀ/TfOH
ß 2014 Elsevier B.V. All rights reserved.
Competitive nitration
Substrate selectivity
Isodesmic proton transfer
1. Introduction
was disclosed by Umemoto and Chika in a patent [10]. The p-tolyl-
SF5 was dinitrated with HNO3/fuming H2SO4, then side-chain
Synthesis of SF5-aromatics continues to be a very active
research area and considerable research effort is being directed
to the development of methodology to synthesize SF5-bearing
building blocks for elaboration into pharmaceuticals, agrochem-
icals, and materials [1,2]. Incorporation of SF5 group(s) imparts
favorable physical and chemical characteristics including thermal,
hydrolytic, and chemical stability, high density, high electronega-
tivity, and high lipophilicity. Whereas a great majority of the
reported methods for the synthesis of SF5-aromatics begin with
nitro-pentafluorosulfanyl benzenes [3–6], access to these com-
pounds has been a major impeding factor to wider synthetic
application [7].
oxidation and decarboxylation furnished the 3,5-dinitro-SF5-
benzene [10].
In continuation of our earlier efforts directed toward the
development of new methods for the synthesis of SF5-aromatics
[11] and our long standing interest in aromatic nitration [12] we
report an alternative and convenient electrophilic method for the
synthesis of the nitro-derivatives by using nitronium salt.
Competiꢀtive nitration (PhSF5 vs PhCF3 and PhSF5 vs PhNO2) with
NO2+BF4 were also performed to gauge relative reactivity, and
relative benzenium ion stabilities were calculated by DFT via
isodesmic reactions.
The m-nitro and p-nitro derivatives have been accessible via the
reaction of isomeric bis(nitrophenyl)disulfides with F2/N2 [8] but
development of alternative, more practical, methods to elemental
fluorination are highly desirable. To that end, Sergeeva and Dolbier
[9] reported direct electrophilic nitration of PhSF5 with H2SO4/
HNO3/TFA in 87% yield. Preparation of the 3,5-dinitro-SF5-benzene
2. Results and discussion
Mechanistic and synthetic aspects of aromatic nitration were
extensively studied by Olah et al. over several decades [13].
Experimental and theoretical studies firmly established the
concept of protosolvation of the nitronium ion leading to increased
reactivity [14,15].
Considering the strongly deactivating effect of SF5
(sp = +0.68)
*
Corresponding author. Tel.: +1 904 620 1503; fax: +1 904 620 3535.
E-mail address: Kenneth.laali@UNF.edu (K.K. Laali).
[1] nitration with the nitronium salt and protosolvation with triflic
http://dx.doi.org/10.1016/j.jfluchem.2014.06.024
0022-1139/ß 2014 Elsevier B.V. All rights reserved.

T. Okazaki, K.K. Laali / Journal of Fluorine Chemistry 165 (2014) 96–100
97
Table 1
Surprisingly, nitration of the mono-nitro derivative 2 with
NO2+BF4ꢀ in CH2Cl–CH2Cl (DCE) as solvent under reflux or in TfOH/
DCE at 70 8C were unsuccessful and 2 was recovered (Table S1 in
supplementary information).
Nitration of PhSF5 with nitronium tetrafluoroborate under various conditions.
Nitration of 1-methyl-4-(pentafluorosulfanyl)benzene 7 with
NO2BF4 in DCM at room temperature gave the mononitro
derivative 1-methyl-2-nitro-4-(pentafluorosulfanyl)benzene 8 in
89% yield (Table 2). Use of excess amounts of NO2BF4 in DCE as
solvent at 70 8C did not lead to dinitration and the mononitrated
product 8 was obtained in 89% yield.
.
Solvent
NO2BF4
Temp.
Time
2 (isolated
yield, %)a
Heating in neat TfOH at 70 8C with excess nitronium
tetrafluoroborate furnished the desired 2-methyl-1,3-dinitro-5-
(pentafluorosulfanyl)benzene 9, along with 5-(fluorosulfonyl)-2-
methyl-1,3-dinitrobenzene 10, and 1-(fluorosulfonyl)-4-methyl-
benzene 11 in 77:19:4 ratio by 1H NMR. Silica gel column
chromatography purification afforded pure 9 in 47% isolated yield
and 5-(fluorosulfonyl)-2-methyl-1,3-dinitrobenzene 10 in 18%
yield.
CH2Cl2
1.7 eq
1.1 eq
1.1 eq
1.5 eq
8.3 eq
15 eq
rt
rt
rt
rt
1d
61b
44b
CH2Cl2
18 h
1d
TfOH/CH2Cl2
TfOH (neat)
CH2Cl2
100c
66b
14 h
then reflux for 3 h
rt for 4 d; 40 8C for
5 h; 70 8C for 14 h
83c
TfOH (neat)
3. Substrate selectivity in competitive nitration
The –SF5, –NO2, and –CF3 groups represent the extreme
examples of deactivating meta directing substitutents in SEAr
chemistry (sm and sp are 0.61 and 0.68 for SF5, 0.71 and 0.78 for
NO2, and 0.43 and 0.54 for CF3) [16].
In the context of the present nitration study it was relevant to
measure substrate selectivity for PhSF5 vs PhNO2 and PhSF5 versus
PhCF3.
(82:9:9 by NMR; before chromatographic isolation)
a
Isolated yield after SiO2 column chromatography.
b
Traces of the p-nitro isomer was detected.
c
Crude product was found to be pure except for a trace of the p-nitro isomer.
Nitronium tetrafluoroborate was added to 1:1 mixture of
substrates in DCM, and after 8 h mixing at room temperature an
aliquot was withdrawn, diluted with CDCl3 and examined directly
by NMR. Substrate selectivity was derived based on the ratio of the
corresponding nitro-products (Tables 3 and 4).
In competitive nitration of PhSF5 vs PhCF3 (Table 3) the
C6H5SF5/NO2–C6H4–SF5 ratio was 87:13 whereas PhCF3/NO2–
C6H4–CF3 was 5:95, consistent with stronger deactivating effect
of the SF5 substituent, leading to a ratio of nitration rate constants
acid were considered as attractive direct one-pot methods for
ArSF5 nitration.
Nitration of PhSF5 1 with nitronium tetrafluoroborate was
carried out under heterogeneous conditions in DCM at room
temperature and after 1 day 1-nitro-3-(pentafluorosulfanyl)ben-
zene 2 was obtained in 61% yield (Table 1). A small amount of 1-
nitro-4-(pentafluorosulfanyl)benzene
3 was detected in the
product mixture by 1H NMR analysis. Nitration with 1.1 equiv.
of NO2BF4 in TfOH/DCM resulted in near quantitative conversion to
2, whereas nitration in neat TfOH at room temperature gave 2 in
66% yield. Both 1 and 2 were found to be stable in TfOH (no side
reactions).
kPhCF =kPhSF ¼ 21:3. After
1 day, the PhCF3 was completely
3
5
nitrated.
In competitive nitration of PhSF5 vs PhNO2 after 7 h the C6H5–
SF5/SF5–C6H4(NO2) and PhNO2/C6H4(NO2)2 ratios were about equal
(97:3) and after 1 day the ratios were 87:13 and 91:9. The data
suggests a kPhNO =kPhSF ¼ ꢁ 1 showing similar deactivating effects.
The use of excess NO2BF4 in DCM without TfOH resulted only in
2, and refluxing in DCM after 3 h showed just a trace of the dinitro-
derivative 4. Increasing the temperature to 70 8C gave a mixture of
2, 4, and 5 in 82:9:9 ratio by 1H NMR (Table 1).
Nitration of 2 in TfOH at 70 8C after 14 days (Scheme 1) gave a
mixture of 4, 6, and 5 (Scheme 1) in 85:10:5 ratio by 1H NMR. Silica
gel column chromatographic separation afforded pure 4 in 17%
yield, 6 in 2% yield, and 5 in 1% yield.
3
5
Focusing on benzenium ion stabilities, and as an extension of
the substrate selectivity measurements, relative energies of the
meta protonated benzenium ions were calculated from the
isodesmic reactions (Eq. (1)) with R = H, NO2 and CF3 by the DFT
method at various levels and by incorporating solvent effect (PCM)
(supplementary information).
SO2F
SO2F
SF5
SF5
NO2BF4
+
+
TfOH
O2N
NO2
NO2
O2N
NO2
70 oC, 14 h
NO2
6
4
5
2
(85: 10: 5 by NMR before chromatographic isolation)
17%
1%
2%
After SiO2 column chromatography
Scheme 1. Dinitration of PhSF5 with nitronium tetrafluoroborate in TfOH.

98
T. Okazaki, K.K. Laali / Journal of Fluorine Chemistry 165 (2014) 96–100
Table 2
Nitration of 7 with nitronium tetrafluoroborate.
.
Solvent
NO2BF4
Temp.
Time
Product
Isolated yield, %a
CH2Cl2
1.3 eq
2.6 eq
2.2 eq
rt
19 h
15 h
3 d
8
8
89
89
ClCH2CH2Cl
TfOH
70 8C
70 8C
(77:19:4 in crude product mixture)
47%
18%
(trace)b
a
Isolated yield after SiO2 column chromatography.
Detected by NMR in the crude reaction mixture.
b
Table 3
Competitive nitration of PhSF5 versus PhCF3.
CF3
CF3
SF5
SF5
NO2BF4
CH2Cl2
.
+
+
NO2
NO2
Reagenta
Temp.
Time
Product ratio, m-NO2:H
Rate ratio
SF5
CF3
CF3/SF5
NO2BF4/CH2Cl2
rt
8 h
13:87
68:32
95:5
21.3
–
1 d
100:0
a
1:PhCF3:NO2BF4 = 1:1:1.3.
Table 4
Competitive nitration PhSF5 versus PhNO2.
NO2
NO2
SF5
SF5
NO2BF4
CH2Cl2
.
+
+
NO2
NO2
Reagenta
Temp.
Time
Product ratio, m-NO2:H
Rate ratio
SF5/NO2
SF5
NO2
NO2BF4/CH2Cl2
rt
7 h
3:97
3:97
9:91
1
1 d
13:87
1.4
a
1:PhNO2:NO2BF4 =1:1:1.3.
R
F5S
R
F5S
+
+
(1)
H
H
H
H

T. Okazaki, K.K. Laali / Journal of Fluorine Chemistry 165 (2014) 96–100
99
According to energy changes for the isodesmic reactions, the
relative stability order CF3 > SF5 ꢁ NO2 was obtained for the
protonation carbocations. In all cases (R = SF5, NO2, and CF3)
formation of the benzenium ions of meta nitration is favored
relative to other isomers.
In summary an alternative method for the synthesis of mono-
and dinitro-derivatives of PhSF5 and tolyl-SF5 are reported by
employing [NO2][BF4] and [NO2][BF4]/TfOH. Substrate selectivity
in competitive nitration reactions underscores the stronger
deactivating power of SF5 relative to CF3, placing it on about
equal footing with NO2.
6, and 5 in 85:10:5 ratio by NMR. The product mixture was purified
by SiO2 column chromatography. The first eluted product with 7:3
hexane–CH2Cl2 wasthe1,3-dinitro-derivative4(11.0 mg, 17%). The
second eluted compound (with 1:1 hexane–CH2Cl2) was compound
5 (0.5 mg, 1%) and the third eluted compound (with 4:6 hexane–
CH2Cl2) was the compound 6 (1.2 mg, 2%).
1-(Fluorosulfonyl)-3-nitrobenzene 5 [17]: colorless oil. MS (GC,
EI) m/z = 205(M+), 189(M+–O), 92; 1H NMR (500 MHz, CDCl3)
d
8.89
(t, J = 2.0 Hz, 1H), 8.65(dd, J = 8.2, 2.0 Hz, 1H), 8.36(d, J = 8.2 Hz, 1H),
7.91 (t, J = 8.2 Hz, 1H); 19F NMR (470 MHz, CDCl3)
66.5 (s, 1F).
d
1-(Fluorosulfonyl)-3,5-dinitrobenzene 6: colorless crystals; mp
124.0–126.0 8C; IR (HATR, cmꢀ1) 2098, 1622, 1600, 1541, 1423,
1344, 1221, 1082; MS (GC, EI) m/z = 250 (M+), 234 (M+–O); 1H NMR
4. Experimental
(500 MHz, CDCl3)
13C NMR (125 MHz, CDCl3)
125.0 (CH); 19F NMR (470 MHz, CDCl3)
d
9.43 (t, J = 1.9 Hz, 1H), 9.17 (d, J = 1.9 Hz, 2H);
149.1 (2 C), 136.8 (C), 128.5 (2CH),
67.2 (s, 1F).
4.1. General
d
d
NMR spectra were recorded on a 500 MHz spectrometer at
room temperature. IR data were collected by using an FT-IR
instrument with HATR attachment. Electron ionization mass
spectra (EI-MS) were measured with a GC–MS instrument. The
reagents were commercially available and were used without
purification.
1,3-Dinitro-5-(pentafluorosulfanyl)benzene 4: colorless oil; IR
(HATR, cmꢀ1) 3111, 2922, 1545, 1348; MS (GC, EI) m/z = 294 (M+),
278 (M+–O), 275 (M+–F); 1H NMR (500 MHz, CDCl3)
d
9.25 (t,
J = 1.9 Hz, 1H), 8.96 (d, J = 1.9 Hz, 2H); 13C NMR (125 MHz, CDCl3)
d
154.5 (apparent triplet, JC–F = 20 Hz, C), 148.3 (2C), 126.8 (quintet,
JC–F = 4.6 Hz, 2CH), 121.7 (CH); 19F NMR (470 MHz, CDCl3)
(quintet, J = 151 Hz, 1F), 63.3 (d, J = 151 Hz, 4F).
d 78.2
4.2. Nitration with nitronium tetrafluoroborate
4.2.3. 1-Methyl-2-nitro-4-(pentafluorosulfanyl))benzene 8
4.2.1. 1-Nitro-3-(pentafluorosulfanyl)benzene 2
In CH2Cl2 at room temperature: A mixture of 1-methyl-4-
(pentafluorosulfanyl) benzene 7 (13.7 mg, 0.0628 mmol) and
NO2BF4 (11.2 mg, 0.0845 mmol) in dry CH2Cl2 (1.30 g) was stirred
at room temperature for 19 h. The mixture was quenched with ice,
washed with 10% Na2CO3, and dried with MgSO4. Removal of the
solvent afforded a colorless oil, which was purified with SiO2
column chromatography with 8:2 hexane–CH2Cl2 as eluent to give
1-methyl-2-nitro-4-(pentafluorosulfanyl)benzene 8 as a colorless
oil (14.7 mg, 89%).
In
CH2Cl2:
1-(Pentafluosulfonyl)benzene
1
(12.1 mg,
0.0593 mmol) was added to a mixture of NO2BF4 (13.0 mg,
0.0979 mmol) in dry CH2Cl2 (0.13 g) and the mixture was stirred
at room temperature for 1 day. After addition of ice, the resulting
mixture was washed with 10% Na2CO3 and dried with MgSO4.
Removal of the solvent gave a colorless oil which was purified with
SiO2 column chromatography with 7:3 hexane–CH2Cl2 as eluent to
give the title product 2 as colorless oil (9.0 mg, 61%).
˚
In CF3SO3H: 1-(Pentafluorosulfanly)benzene
1
(10.0 mg,
In ClCH2CH2Cl (DCE) at 70 C:
(pentafluorosulfanyl)benzene
A
mixture of 1-methyl-4-
0.0490 mmol) was added to mixture of NO2BF4 (9.9 mg,
a
7
(23.1 mg, 0.106 mmol) and
0.075 mmol) in CF3SO3H (0.19 g) and the reaction mixture was
stirred at room temperature for 18 h. After addition of ice, the
resulting mixture was washed with 10% Na2CO3 and dried with
MgSO4. Removal of the solvent gave a colorless oil, which was
purified with SiO2 column chromatography with 7:3 hexane–CH2Cl2
as eluent to give the title product 2 as colorless oil (8.1 mg, 66%).
1-Nitro-3-(pentafluorosulfanyl)benzene 2: 1H NMR (500 MHz,
NO2BF4 (36.3 mg, 0.273 mmol) in dry DCE (0.76 g) was heated
in an oil bath at 70 8C for 3 day. The mixture was quenched with ice
and extracted with CH2Cl2. The organic layer was washed with 10%
Na2CO3, and dried with MgSO4. Removal of the solvent afforded a
pale yellow oil, which was purified with SiO2 column chromatog-
raphy with 8:2 hexane–CH2Cl2 as eluent to give 1-methyl-2-nitro-
4-(pentafluorosulfanyl)benzene 8 as a colorless oil (24.7 mg, 89%).
1-Methyl-2-nitro-4-(pentafluorosulfanyl)benzene 8 [10,3a]: 1H
CDCl3)
d
8.66 (s, 1H), 8.43 (d, J = 8.2 Hz, 1H), 8.12 (d, J = 8.2 Hz, 1H),
154.1 (quintet,JC–
7.74(t,J = 8.2 Hz,1H);13CNMR(125 MHz, CDCl3)
d
NMR (500 MHz, CDCl3)
2.2 Hz, 1H), 7.50 (d, J = 8.5 Hz, 1H), 2.69 (s, 3H); 13C NMR (125 MHz,
CDCl3) 151.7 (apparent triplet, J = 20 Hz, C), 148.5 (C), 137.7 (C),
d 8.40 (d, J = 2.2 Hz, 1H), 7.89 (dd, J = 8.5,
F = 19.5 Hz, C), 147.9 (C),131.7 (quintet, JC–F = 4.6 Hz,CH),130.0(CH),
126.4 (CH), 121.8 (quintet, JC–F = 4.6 Hz, CH); 19F NMR (470 MHz,
d
CDCl3)
d
81.1 (quintet, J = 151 Hz, 1F), 62.8 (d, J = 151 Hz, 4F).
133.3 (CH), 130.0 (quintet, JC–F = 4.6 Hz, CH), 122.9 (quintet, JC–
F = 4.6 Hz, CH), 20.4 (CH3); 19F NMR (470 MHz, CDCl3)
d 81.8
4.2.2. 1,3-Dinitro-5-(pentafluorosulfanyl)benzene 4
(quintet, J = 151 Hz, 1F), 63.0 (d, J = 151 Hz, 4F).
˚
1-(Pentafluorosulfanyl)benzene 1 (9.8 mg, 0.048 mmol) was
added to NO2BF4 (92.6 mg, 0.697 mmol) in CF3SO3H (0.19 g) and
the mixture was heated at 70 8C for 14 h. After cooling, ice was
added and the resulting mixture was extracted with CH2Cl2. The
organic layer was washed with 10% Na2CO3 and dried with MgSO4.
Removal of the solvent gave a colorless oil (9.9 mg) that was
examined by NMR showing the formation of 1-nitro-3-(penta-
fluorosulfanyl)benzene 2, 1,3-dinitro-5-(pentafluorsulfanyl)ben-
zene 4 and the –SO2F derivative 5 in 82:9:9 ratio.
In CF3SO3H at 70 C: A mixture of 8 (24.3 mg, 0.111 mmol) and
NO2BF4 (32.1 mg, 0.242 mmol) in dry TfOH (0.18 g) was heated
with in an oil bath at 70 8C for 3 day. The mixture was quenched
with ice and extracted with CH2Cl2. The organic layer was washed
with 10% Na2CO3 and dried with MgSO4. Removal of the solvent
afforded pale-brown crystals whose NMR analysis indicated the
formation of 9, 10, and 11 in ratio 77:19:4. The products were
purified with SiO2 column chromatography. By using hexane–
CH2Cl2 (7:3) as eluent, compound 9 was obtained as colorless
crystals (16.1 mg, 47%). Compound 10 was isolated as a pale-
yellow solid by using 1:1 hexane–CH2Cl2 as eluent (5.3 mg, 18%).
1-(Fluorosulfonyl)-4-methylbenzene 11 [18]: 1H NMR
1-Nitro-3-(pentafluorosulfanyl)benzene
2
(53.5 mg,
0.048 mmol) was added to NO2BF4 (115.1 mg, 0.697 mmol) in
CF3SO3H (0.19 g) and the mixture was heated at 70 8C for 14 day.
Aftercooling,icewasaddedandtheresultingmixturewasextracted
with CH2Cl2. The organic layer was washed with 10% Na2CO3 and
dried with MgSO4. The removal of the solvent gave a colorless oil
(12.7 mg), whose NMR measurement showed the formation of 2, 4,
(500 MHz, CDCl3)
d
7.90 (dd, J = 8.2 Hz, 2H), 7.43 (d, J = 8.2 Hz,
66.2 (s, 1F).
2H), 2.50 (s, 3H); 19F NMR (470 MHz, CDCl3)
d
2-Methyl-1,3-dinitro-5-(pentafluorosulfanyl)benzene 9 [10]:
mp 108.0–109.0 8C; MS (GC, EI) m/z = 308 (M+), 291 (M+–HO),

100
T. Okazaki, K.K. Laali / Journal of Fluorine Chemistry 165 (2014) 96–100
274 (M+–H2O2) 261 (M+–HNO2); 1H NMR (500 MHz, CDCl3)
(s, 2H), 2.67 (s, 3H); 13C NMR (125 MHz, CDCl3)
151.4 (apparent
d
8.40
Appendix A. Supplementary data
d
triplet, J = 20 Hz, C), 151.2 (2C), 131.4 (C), 125.2 (quintet, JC–
Supplementarydataassociatedwiththisarticlecanbefound, inthe
online version, at http://dx.doi.org/10.1016/j.jfluchem.2014.06.024.
F = 5.1 Hz, 2CH), 15.3 (CH3); 19F NMR (470 MHz, CDCl3)
d 78.7
(quintet, J = 152 Hz, 1), 63.3 (d, J = 152 Hz, 4F).
5-(Fluorosulfonyl)-2-methyl-1,3-dinitrobenzene 10: mp 74.5–
75.5 8C; IR (ATR, cmꢀ1) 3090, 1541, 1423, 1346, 1219; MS (GC, EI)
References
264 (M+), 247 (M+–HO); 1H NMR (500 MHz, CDCl3)
d
8.60 (s, 2H),
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2.74 (s, 3H); 13C NMR (125 MHz, CDCl3)
d 152.0 (2C), 135.3 (C),
133.1 (C), 126.9 (2CH), 15.8 (CH3); 19F NMR (470 MHz, CDCl3)
67.4 (s, 1F).
d
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ˇ´
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[7] The para and meta nitro isomers are commercially available but they are rather
pricy!
NO2BF4 (0.062 mmol) was added to a 1:1 mixture of (penta-
fluorosulfanyl)benzene (1, 0.049 mmol) and nitrobenzene
(0.049 mmol) or (trifluoromethyl)benzene (0.05 mmol) in dry
CH2Cl2 (0.5 ml) with efficient stirring at room temperature.
Aliquots were withdrawn at different intervals and diluted with
CDCl3 for direct NMR analysis to determine product distribution.
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[12] (a) See for example: G. Aridoss, K.K. Laali, J. Org. Chem. 76 (2011) 8088–8094;
(b) J. Jacoway, G.G.K.S. Narayana Kumar, K.K. Laali, Tetrahedron Lett. 53 (2012)
6782–6785;
4.3.1. (Pentafluorosulfanyl)benzene (1) and (trifluoromethyl)benzene
NO2BF4 (8.2 mg, 0.062 mmol) was added into a solution of 1
(9.9 mg, 0.048 mmol) and (trifluorobenzene) (7.2 mg, 0.049 mmol)
in dry CH2Cl2 (0.7228 g), and the mixture was efficiently stirred.
(c) K.K.Laali,M.A.Arrica,T.Okazaki,R.G.Harvery,J.Org.Chem.72(2007)6768–6775;
(d) K.K. Laali, J.H. Chun, T. Okazaki, S. Kumar, G.L. Borosky, C. Swartz, J. Org. Chem. 72
(2007) 8383–8393;
(e) C.Brule,K.K.Laali,T.Okazaki,T.Musafia,W.M.Baird,Eur.J.Org.Chem.(2007)487–
497;
(f) K.K. Laali, V.J. Gettwert, J. Org. Chem. 66 (2001) 35–40.
4.3.2. (Pentafluorosulfanyl)benzene (1) and nitrobenzene
NO2BF4 (8.2 mg, 0.062 mmol) was added into a solution of 1
(10.0 mg,
0.049 mmol)
and
(trifluorobenzene)
(6.0 mg,
[13] G.A. Olah, R. Malhotra, S.C. Narang, Nitration Methods and Mechanisms, VCH,
Weinheim, 1989.
[14] (a) G.A. Olah, K.K. Laali, Q. Wang, G.K.S. Prakash, OniumIons, Wiley, New York, 1998;
(b) G.A. Olah, G.K.S. Prakash, A. Molnar, J. Sommer, Superacid Chemistry, 2nd ed.,
Wiley, Hoboken, NJ, 2009.
0.049 mmol) in dry CH2Cl2 (0.7900 g), and the mixture was
efficiently stirred.
Note: NO2BF4 is not soluble in DCM and withdrawal of aliquots
at intervals for NMR analysis inevitably leads to gradual increase in
molar equivalents of NO2BF4 in the reaction mixture.
[15] G.A. Olah, D.A. Klumpp, Superelectrophiles and their Chemistry, Wiley, Hobo-
ken,NJ, 2008.
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[18] G. Ung, G. Bertrand, Chem. Eur. J. 18 (2012) 12955–12957.
[19] W. Koch, M.C. Holthausen, A Chemist’s Guide to Density Functional Theory, 2nd
ed., Wiley-VCH, Weinheim, 2000.
5. DFT calculations
[20] M.J. Frisch, G.W. Trucks, H.B. Schlegel, G.E. Scuseria, M.A. Robb, J.R. Cheeseman,
J.A. Montgomery Jr., T. Vreven, K.N. Kudin, J.C. Burant, J.M. Millam, S.S. Iyengar, J.
Tomasi, V. Barone, B. Mennucci, M. Cossi, G. Scalmani, N. Rega, G.A. Petersson, H.
Nakatsuji, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T.
Nakajima, Y. Honda, O. Kitao, H. Nakai, M. Klene, X. Li, J.E. Knox, H.P. Hratchian, J.B.
Cross, V. Bakken, C. Adamo, J. Jaramillo, R. Gomperts, R.E. Stratmann, O. Yazyev,
A.J. Austin, R. Cammi, C. Pomelli, J.W. Ochterski, P.Y. Ayala, K. Morokuma, G.A.
Voth, P. Salvador, J.J. Dannenberg, V.G. Zakrzewski, S. Dapprich, A.D. Daniels, M.C.
Strain, O. Farkas, D.K. Malick, A.D. Rabuck, K. Raghavachari, J.B. Foresman, J.V.
Ortiz, Q. Cui, A.G. Baboul, S. Clifford, J. Cioslowski, B.B. Stefanov, G. Liu, A.
Liashenko, P. Piskorz, I. Komaromi, R.L. Martin, D.J. Fox, T. Keith, M.A. Al-Laham,
C.Y. Peng, A. Nanayakkara, M. Challacombe, P.M.W. Gill, B. Johnson, W. Chen,
M.W. Wong, C. Gonzalez, J.A. Pople, Gaussian 03, Revision E.01, Gaussian, Inc.,
Wallingford, CT, 2004.
Structures were optimized using tight convergence by the DFT
method at B3LYP/6-31G(d) and B3LYP/6-311+G(d,p) levels using
the Gaussian 03 package [19,20]. All computed geometries were
verified by frequency calculations to have no imaginary frequen-
cies. Solvent effects are computed using the polarizable continuum
model (PCM) [21].
Acknowledgement
KL thanks UNF for the Presidential Professor award and
research support.
[21] J. Tomasi, B. Mennucci, R. Cammi, Chem. Rev. 105 (2005) 2999–3094.