Fluorination of Bi- and polycyclic aromatic hydrocarbons with N-fluorobis(phenylsulfonyl)amine in the absence of solvent

Article abstract of DOI:10.1134/S1070428010090095

Reactions of N-fluorobis(phenylsulfonyl)amine with naphthalene, 1-methylnaphthalene, phenanthrene, anthracene, and pyrene without solvent were investigated. Sometimes the fluorination of aromatic compounds with N-fluorobis(phenylsulfonyl)amine without solvent proceeded more selectively than at the use of fluorinating reagents in solution.

Full text of DOI:10.1134/S1070428010090095

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2010, Vol. 46, No. 9, pp. 1317−1322. © Pleiades Publishing, Ltd., 2010.
Original Russian Text © G.I. Borodkin, I.R. Elanov, V.G. Shubin, 2010, published in Zhurnal Organicheskoi Khimii, 2010, Vol. 46, No. 9, pp. 1318−1323.
Fluorination of Bi- and Polycyclic Aromatic Hydrocarbons
with N-Fluorobis(phenylsulfonyl)amine
in the Absence of Solvent
G. I. Borodkin, I. R. Elanov, and V. G. Shubin
Vorozhtsov Novosibirsk Institute of Organic Chemistry, Siberian Division, Russian Academy of Sciences,
Novosibirsk, 630090 Russia
e-mail: gibor@nioch.nsc.ru
Received December 30, 2009
Abstract—Reactions of N-fluorobis(phenylsulfonyl)amine with naphthalene, 1-methylnaphthalene, phenanthrene,
anthracene, and pyrene without solvent were investigated. Sometimes the fluorination of aromatic compounds
with N-fluorobis(phenylsulfonyl)amine without solvent proceeded more selectively than at the use of fluorinating
reagents in solution.
DOI: 10.1134/S1070428010090095
fluorination selectivity of bi- and polycyclic aromatic
hydrocarbons with NFSI reagent in the absence of sol-
vent. The problem of the selectivity of the electrophilic
fluorination under these conditions is poorly understood
(cf. [17, 22]).
In the last two decades the direct electrophilic fluorina-
tion of organic compounds is often performed with the
use of NF-reagents: N-fluorobis(phenylsulfonyl)amine
(NFSI), salts of N-fluoropyridinium, N-fluoroquinucli-
dinium, 1-R-4-fluoro-1,4-diazoniabicyclo[2.2.2]octane
(R = CH2Cl, OH) etc. [1–20]. The solvents commonly
used in the fluorination with these reagents are acetoni-
trile, dichloroethane, dichloromethane, and methanol.
The replacement of toxic solvents or their exclusion from
the process is an important task of the “green chemistry”
[21–23].
We found that the naphthalene (I) fluorination with
NFSI reagent in the absence of solvent provided prevail-
ingly 1-fluoro- (II), 2-fluoro- (III), and 1,4-difluoronaph-
thalene (IV) (Scheme 1, Table 1).
The yield of the product of difluorination IV at 115°C
and the ratio NFSI–ArH 1 : 1 grew with the growing
reaction duration from 10 min to 1 h and afterwards
remained practically constant. On increasing the ratio
NFSI–ArH from 1 : 1 to 2 : 1 and the reaction time to 5 h
the relative fraction of difluoride IV grew, but the further
increase in this ratio resulted in reduction in the yield of
the fluorination products apparently due to the oxidation
We showed formerly that the electrophilic fluorination
of methyl-substituted benzenes, phenols, and their ethers
could be performed with NFSI reagent in the absence of
solvent, sometimes with a higher selectivity than in the
presence of solvents [22].
The goal of this study was the investigation of the
Scheme 1.
F
F
F
NFSI
+
+
F
I
II
IV
III
1317

BORODKIN et al.
1318
processes (cf. [5, 12, 24]). 1,4-Difluoronaphthalene evi-
dently formed by the fluorination of arising in the reaction
1-fluoronaphthalene. The growth of the relative fraction
of the difluoride in the mixture of the products with the
increasing ratio NFSI–naphthalene is apparently caused
by the greater reactivity of 1-fluoronaphthalene compared
with naphthalene, in agreement with the electrophilic
character of the reaction (cf. [25]). Practically in all
events at the equimolar ratio of the substrate and the re-
agent a significant regioselectivity of the fluorination was
observed: The ratio 1-fluoro-/2-fluoronaphthalene was in
the range from 5 : 1 to 7 : 1. On decreasing the reaction
temperature from 115 to 90°C this ratio increased. The
use as solvent of acetonitrile, ethanol, or dichloroethane
resulted in practically the same regioselectivity (at 115°C
the regioselectivity of the fluorination characterized by the
ratio 1-fluoronaphthalene–2-fluoro-naphthalene changed
from 5 : 1 to 7 : 1), the overall yield of the fluorination
products in EtOH and ClCH2CH2Cl was lower than in
the reaction without solvent.
Similar regioselectivity was formerly observed at
the use of reagents XeF2 and CsSO4F in the presence of
BrØnsted or Lewis acids (Table 2). The use of reagent F-
TEDA-BF4 combined with BrØnsted acids led to a lower
regioselectivity. A higher regioselectivity was obtained
at the application of CsSO4F in MeCN, (CF3SO2)2NF
and CDCl3 and 1-chloromethyl-4-fluoro-1,4-diazoniab-
icyclo[2.2.2]octane bistetrafluoroborate (F-TEDA-BF4)
in a ionic liquid, 1-methyl-3-ethylimidazolium triflate
[emim][CF3SO3] (Table 2).
Table 1. Fluorination of naphthalene and 1-methylnaphthalene with N-fluorobis(phenylsulfonyl)amine without solvent
Compound no.
NFSI–ArH
1 : 1
1 : 1
1 : 1
1 : 1
1 : 1
1 : 1
1 : 1
1 : 1
1 : 1
1 : 2
1 : 4
2 : 1
2 : 1
4 : 1
1 : 1
1 : 1
1 : 1
1 : 1
1 : 1
1 : 2
1 : 4
1 : 1
Temperature, °C
115
Time, h
Yield of reaction products, %a
II (13), III (2), IV (1)
Overall yield, %
I
0.17
0.5
1
16
28
30
32
32
31
32
12
26
42
45
21
21
1
I
115
II (20), III (4), IV (4)
I
115
II (21), III (4), IV (5)
I
115
2
II (23), III (4), IV (5)
I
115
3
II (22), III (4), IV (6)
I
115
5
II (22), III (4), IV (5)
I
115
21
1
II (22), III (4), IV (6)
I
90
II (10), III (1.5), IV (0.5)
II (19), III (3), IV (4)
I
90
5
I
115
4.5
4.5
0.17
5
II (33), III (6), IV (3)
I
115
II (37), III (6), IV (2)
I
115
II (16), III (3), IV (2)
I
115
II (8), III (2), IV (11)
I
115
5
II (0.2), III (0.2), IV (0.6)
II (27), III (4), IV (3)
Ib
Ic
Id
V
V
V
V
Vb
115
1
34
10
18
11
18
19
21
24
115
1
II (8), III (1.5), IV (0.3)
II (15), III (2), IV (0.7)
VI (3), VII (6), VIII (1), IX (1)
VI (4), VII (10), VIII (2) IX (2)
VI (5), VII (10), VIII (2) IX (2)
VI (5), VII (12), VIII (2) IX (2)
VI (6), VII (13), VIII (2) IX (3)
115
1
115
0.17
1
115
115
1
115
1
115
1
a
In all cases save the runs with deficit of NFSI the yields were determined with respect to the substrate, and at substrate excess, with respect
to the reagent.
b In acetonitrile.
c
In dichloroethane.
d In ethanol.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 46 No. 9 2010

FLUORINATION OF BI AND POLYCYCLIC AROMATIC HYDROCARBONS
1319
Table 2. Ratio of 1-fluoro- and 2-fluoronaphthalenes at the direct fluorination under various conditions
Molar ratio
Reagent
Solvent (catalyst)
Temperature, °C 1-fluoronaphthalene–2-fluoronaph-
Reference
thalene
(CF3SO2)2NF
F-TEDA-BF4
F-TEDA-BF4
F-TEDA-BF4
CsSO4F
CDCl3
22
80
11
13
3
[26]
[19]
[27]
[28]
[29]
[29]
[29]
[29]
[29]
[29]
[30]
[31]
[emim][CF3SO3]
CF3COOH
70
CF3SO3H–CH2Cl2
MeCN
boiling
20
1.5
~40
6
CsSO4F
MeCN (HF)
MeCN (H2SO4)
MeCN (BF3)
MeCN (CF3SO3H)
MeCN (HSO3F)
MeCN (BF3)
CH2Cl2
20
CsSO4F
20
5
CsSO4F
20
4
CsSO4F
20
4
CsSO4F
20
4
CsSO4F
20
5
XeF2
–196–20
4.5
The fluorination of 1-methylnaphthalene (V) with
NFSI reagent without solvent occurs nonselectively
affording 1-methyl-2-fluoro- (VI), 1-methyl-4-fluoro-
(VII), 1-methyl-5-fluoro- (VIII), and 1-methyl-8-fluoro-
naphthalenes (IX) (Scheme 2). The yield of fluorination
products somewhat grows at the ratio NFSI–1-methyl-
naphthalene decreased from 1 : 1 to 1 : 4 (Table 1). The
isomers ratio (VI) : (VII) : (VIII) : (IX) in the fluorination
of the 1-methylnaphthalene with the NFSI reagent without
solvent was close to this ratio observed in acetonitrile
(Table 1) and also at the use of F-TEDA-BF4 reagent in
ionic liquid [bmim]PF6 (21 : 53 : 11 : 15) [19].
reagent without solvent formed predominantly 9-fluoro-
phenanthrene (XI) (Scheme 3, Table 3). Alongside this
compound in small quantities formed 1-fluoro-, 3-fluoro-,
4-fluorophenanthrenes (XII–XIV respectively), and also
9,10-difluorophenanthrene (XV).
The variation of the ratio NFSI–substrate and the tem-
perature weakly affected the isomer ratio in the product.
The maximum yield of the fluorination products was
obtained at 115°C and the ratio NFSI–substrate 1 : 2.
As expected, the relative amount of 9,10-difluorophen-
anthrene decreased with the decreasing ratio NFSI–sub-
strate. The prevailing formation of 9-fluorophenanthrene
in the phenanthrene fluorination was also observed at
In the fluorination of phenanthrene (X) with NFSI
Scheme 2.
Me
Me
Me
F
Me
F
Me
F
NFSI
+
+
+
F
V
VI
VIII
IX
VII
Scheme 3.
F
F
F
F
+
NFSI
+
+
+
F
F
XIV
XI
XII
XV
X
XIII
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 46 No. 9 2010

BORODKIN et al.
1320
Table 3. Fluorination of polycyclic arenes with N-fluorobis(phenylsulfonyl)amine without solvent
Compound no. NFSI–ArH Temperature, °C Time, h
Yield of reaction products, %a
0.33 XI (27), XII (2), XIII (1), XIV (1), XV (5)
XI (29), XII (2), XIII (1), XIV (1), XV (5)
Overall yield, %
X
1 : 1
1 : 1
1 : 2
1 : 4
2 : 1
4 : 1
1 : 1
1 : 1
1 : 1
1 : 1
1 : 1
2 : 1
1 : 2
1 : 4
1 : 1
1 : 1
1 : 1
1 : 1
1 : 1
1 : 2
1 : 4
2 : 1
1 : 1
1 : 1
1 : 1
115
105
115
115
115
115
115
115
115
90
36
38
48
32
41
33
28
9
X
1
X
0.33 XI (40), XII (3), XIII (1), XIV (2), XV (2)
0.33 XI (27), XII (2), XIII (1), XIV (1), XV (0.5)
0.33 XI (30), XII (3), XIII (1), XIV (1), XV (6)
0.33 XI (23), XII (3), XIII (1), XIV (1), XV (5)
0.33 XI (21), XII (2), XIII (1), XIV (2), XV (2)
X
X
X
Xb
XVI
XVI
XVI
XVI
XVI
XVI
XVI
XVIb
XIX
XIX
XIX
XIX
XIX
XIX
XIX
XIXb
XIXc
XIXd
1
5
1
1
1
1
1
1
1
1
1
1
1
1
1
1
25
1
XVII (5), XVIII (4)
XVII (4), XVIII (3)
XVII (3), XVIII (2)
XVII (9), XVIII (4)
XVIII (1)
7
5
140
115
115
115
115
115
90
13
1
XVII (10), XVIII (3)
XVII (11), XVIII (3)
XVII (30), XVIII (12)
XX (25), XXI (4)
XX (23), XXI (4)
XX (19), XXI (4)
XX (23), XXI (6)
XX (36), XXI (5)
XX (41), XXI (5)
XX (7), XXI (3)
13
14
42
29
27
23
29
41
46
10
41
40
30
105
140
115
115
115
115
105
115
XX (32), XXI (9)
XX (32), XXI (8)
XX (24), XXI (6)
a
In all cases save the runs with deficit of NFSI the yields were determined with respect to the substrate, and at substrate excess, with respect
to the reagent . bIn acetonitrile. cIn dichloroethane. dIn ethanol.
reagent without solvent at the equimolar ratio NFSI–sub-
strate and 115°C led to the formation predominantly of
9-fluoroanthracene (XVII) and 9,10-difluoroanthracene
(XVIII) in low yields (Scheme 4, Table 3). At the tem-
perature increased to 140°C grew the relative fraction of
the monofluorination product XVII.
the use of acetonitrile as solvent (Table 3), and also at
the application of other reagents: F-TEDA-BF4 [27],
XeF2 [31–33], XeF6 [34], CsSO4F [30], therewith the
products formed of deeper fluorination and oxidation,
9,9,10-trifluoro-9,10-dihydrophenanthrene [32, 34],
9,9,10,10-tetrafluoro-9,10-dihydro-phenanthrene [34],
and 9,9-difluoro-10-keto-9,10-dihydrophenanthrene [30].
The decreased ratio NFSI–substrate also resulted in
the growth of the relative fraction of the monofluorina-
The fluorination of anthracene (XVI) with the NFSI
Scheme 4.
F
F
NFSI
+
F
XVI
XVII
XVIII
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 46 No. 9 2010

FLUORINATION OF BI AND POLYCYCLIC AROMATIC HYDROCARBONS
1321
tion product XVII whereas at the increase in this ratio
formed only 9,10-difluoroanthracene in a low yield. The
ratio of compounds XVII and XVIII weakly depended on
the temperature variation. This ratio is sometimes higher
than at the application of N-fluoro-2,4-dinitroimidazole
in CH2Cl2 [35] or of N-fluoropyridinium triflate in
ClCH2CH2Cl [36]. At the use of the reagent F-TEDA-
BF4 in CF3COOH the fluorination products did not form
at all, and the main product was 9-trifluoroacetoxyan-
thracene [27].
300 (1H), 282.4 MHz (19F)].As internal references served
CHCl3 (δ 7.24 ppm) for H and PhCF3 (δ –63.73 ppm,
1
calculated from CFCl3) for19F. GC-MS measurements
were performed on an instrument Hewlett Packard
G1800A including a gas chromatograph HP 5890 series
II and mass-selective detector HP 5971. The structure of
compounds obtained was confirmed by 1H and 19F NMR
spectra and GC-MS data. The spectral characteristics
were consistent with the published data for 1-fluoro-,
2-fluoro-, 1,4-difluoronaphthalene [26, 38, 39], 1-methyl-
2-fluoro-, 1-methyl-4-fluoro-, 1-methyl-5-fluoro-,
1-methyl-8-fluoronaphthalene [19], 1-fluoro-, 3-fluoro-,
4-fluoro-, 9-fluoro-, 9,10-difluorophenanthrene [32, 34,
40], 9-fluoro-, 9,10-difluoroanthracene [35], 1-fluoro-,
4-fluoropyrene [35, 40].
The fluorination of pyrene (XIX) with the NFSI
reagent at the molar ratio NFSI–substrate 1 : 1 in the ab-
sence of solvent led to predominant formation of 1-fluoro-
(XX) and 4-fluoropyrene (XXI) (Scheme 5, Table 3).
The ratio of products XX–XXI and the yield grew
at the reduction of the molar ratio NFSI–substrate from
1 : 1 to 1 : 4. The increase in the relative content of the
NFSI reagent resulted in the reverse effect apparently due
to the oxidation processes. At the ratio NFSI–substrate
4 : 1 compounds XX and XXI were not detected in the
reaction products. The regioselectivity of the fluorina-
tion is somewhat higher in the process without solvent
than at the use the NFSI reagent with solvents (Table
3), and it increases at lowering the temperature: 140°C
(3.8), 105°C (4.8), and 90°C (5.8). Analogous tempera-
ture effect was observed at the pyrene fluorination with
1-hydroxy-4-fluoro-1,4-diazoniabicyclo[2.2.2]octane
bistetrafluoroborate in MeCN: 80°C (3), 60°C (4), 22°C
(8), 5°C (13) [37].
The following reagents were used in the study: 97% N-
fluorobis(phenylsulfonyl)amine (Aldrich), naphthalene of
“pure for analysis” grade, distilled 1-methyl-naphthalene
of “pure” grade, anthracene of “pure for analysis” grade,
phenanthrene of “pure” grade, pyrene (>95%) (Fluka),
99.9% MeCN (Panreac), EtOH (rectified), distilled
ClCH2CH2Cl of “pure” grade, CDCl3 with deuterium
content 99.8 at%.
General procedure of fluorination with NFSI re-
agent. To 0.2 mmol of an aromatic substrate was added
a desired amount of NFSI reagent in a glass ampule
(molar ratiosArH–NFSI are indicated in Tables 1, 3). The
reaction mixture was maintained at definite temperature,
cooled, 1 ml of CDCl3 or of a mixture CDCl3–(CH2Cl)2,
1 : 1, and a weighed amount of PhCF3 were added, and
the NMR spectra were registered, The yield and the ratio
of the fluorination products were determined from 19F
NMR spectra.
Thus the exclusion of the solvent from the fluorination
process of bi- and polycyclic aromatic hydrocarbons with
NFSI reagent does not considerably affects the reaction
selectivity, but the fluorination regioselectivity of poly-
cyclic hydrocarbons increases.
The maintaining the solutions of aromatic hydro-
carbons and NFSI reagent in solvents MeCN, EtOH,
and (CH2Cl)2 was performed in sealed ampules. The
concentration of substrate solutions was 0.3–1.7 mol l−1.
EXPERIMENTAL
1H and 19F NMR spectra were registered on
a spectrometer Bruker AV-300 [operating frequencies
The study was carried out under a financial support
of the Russian Foundation for Basic Research (grant
Scheme 5.
F
F
NFSI
+
XIX
XX
XXI
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 46 No. 9 2010

BORODKIN et al.
1322
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