A new method for the preparation of fluoro-λ6-sulfanenitriles: Reaction of sulfimides with Selectfluor

Article abstract of DOI:10.1016/S0040-4039(03)01547-8

Several diaryl(fluoro)-λ⁶-sulfanenitriles 3 were synthesized by the reaction of S,S-diarylsulfimides 1 with Selectfluor. This reaction also allows the first preparation of heterocyclic fluoro-λ⁶-sulfanenitrile, 5-fluoro-10,10-dioxo-5,10-dihydro-5λ⁶,10λ ⁶-thianthren-5-nitrile (5) and its molecular structure was determined by X-ray crystallographic analysis.

Full text of DOI:10.1016/S0040-4039(03)01547-8

TETRAHEDRON
LETTERS
Pergamon
Tetrahedron Letters 44 (2003) 6203–6205
A new method for the preparation of fluoro-l6-sulfanenitriles:
reaction of sulfimides with Selectfluor™
Takayoshi Fujii, Shinsuke Asai, Tomoyuki Okada, Wei Hao, Hiroyuki Morita and
Toshiaki Yoshimura*
Department of Material Systems Engineering and Life Science, Faculty of Engineering, Toyama University, Gofuku,
Toyama 930-8555, Japan
Received 2 June 2003; revised 19 June 2003; accepted 20 June 2003
Abstract—Several diaryl(fluoro)-l6-sulfanenitriles 3 were synthesized by the reaction of S,S-diarylsulfimides 1 with Selectfluor™.
This reaction also allows the first preparation of heterocyclic fluoro-l6-sulfanenitrile, 5-fluoro-10,10-dioxo-5,10-dihydro-5l6,10l6-
thianthren-5-nitrile (5) and its molecular structure was determined by X-ray crystallographic analysis.
© 2003 Elsevier Ltd. All rights reserved.
N-Halosulfimides (R2S=NX, X=F, Cl, Br, I) have
attracted much attention because of their unique struc-
tures and reactivities.1–5 We recently have found that
diaryl(fluoro)-l6-sulfanenitriles (Ar2FSꢀN) bearing an
SN triple bond are obtained by the reaction of N-bro-
mosulfimides with a fluoride anion, and we have also
prepared several types of l6-sulfanenitriles by using the
fluoro-l6-sulfanenitriles as the starting materials.5,6 In
fluorine and inorganic chemistry, S,S-difluoro-N-
fluorosulfimide and its structural isomer, trifluoro-l6-
sulfanenitrile (F3SꢀN), were prepared several decades
ago.7,8 In contrast, S-alkyl and -aryl substituted N-
fluorosulfimides are less well-known. S,S-Diaryl-N-
chloro-, -N-bromo-, and -N-iodo-sulfimides were
prepared by halogenation of S,S-diarylsulfimides
(Ar2SꢁNH) 1.4 We, therefore, have examined reaction
of 1 with an electrophilic fluorinating reagent, Select-
fluor™ (1-chloromethyl-4-fluoro-1,4-diazoniabicyclo-
[2,2,2]octane bis(tetrafluoroborate)).9 This work led us
to the finding that the resulting S,S-diaryl-N-fluoro-
sulfimides 2 readily undergo 1,2-migration of the
fluorine atom to form the corresponding diaryl(fluoro)-
l6-sulfanenitriles 3. In addition, we also found that the
reaction of heterocyclic sulfimide, 10,10-dioxo-10H-
5l4,10l6-thianthren-5-ylideneamine (4) with Selec-
tfluor™ affords
a
new type of heterocyclic
fluoro-l6-sulfanenitrile 5.
The reaction of S,S-diphenylsulfimide (1a) with Select-
fluor™ was carried out in CH3CN at 0°C for 3 h
(Scheme 1). A large amount of Na2CO3 was added to
avoid protonation of 1. Separation and purification
from the resulting mixture gave fluoro(diphenyl)-l6-sul-
fanenitrile (3a) in 80% yield,5b,10 and the expected S,S-
Scheme 1. (a) 1 (1 mmol), Selectfluor™ (1 mmol), Na2CO3 (5 mmol), CH3CN (90 ml). (b) Isolated yields.
Keywords: fluoro-l6-sulfanenitriles; sulfimides; Selectfluor™; fluorination; heterocycles; X-ray crystallographic analysis.
* Corresponding author. Fax: +81-76-445-6850; e-mail: yosimura@eng.toyama-u.ac.jp
0040-4039/$ - see front matter © 2003 Elsevier Ltd. All rights reserved.
doi:10.1016/S0040-4039(03)01547-8

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T. Fujii et al. / Tetrahedron Letters 44 (2003) 6203–6205
(NꢂF) gradually diminished and two resonance signals
at l −125.2 and 87.4 appeared. The latter signal was
assigned to that of l6-sulfanenitriles 3d. The former
new signal increased gradually but disappeared soon
and the spectra changed to that of 3d, being indicative
of the existence of intermediate, S-(4-nitrophenyl)-S-
phenyl-N-fluorosulfimide (2d) in the present reaction.
As mentioned above, F2SꢁNF and F3SꢀN were
reported by Glemser and Mews et al.7,8 Theoretical
calculations also indicated that their energy difference is
small.2 We therefore performed calculations on cis- and
trans-S,S-dimethyl-N-fluorosulfimide (2A-cis and 2A-
trans) and dimethyl(fluoro)-l6-sulfanenitrile (3A) as the
model compounds of 2 and 3.11 It was revealed that
N-fluorosulfimides 2A-cis and 2A-trans are 12.1 and
18.0 kcal/mol higher in energy compared to 3A at the
B3LYP/6-311++G(3df, 2pd)//B3LYP/6-31G(d) level
(Fig. 1). These results imply that diary-N-fluorosulfi-
mides 2 should be converted to thermodynamically
stable fluoro-l6-sulfanenitriles 3.
diphenyl-N-fluorosulfimide (2a) was not obtained even
in trace amounts. Similar treatment of arylsulfimides
1b–d also gave the corresponding fluoro-l6-sulfaneni-
triles 3b–d (Scheme 1).5b,10 It is well known that the
nitrogen atom of sulfimides has a nucleophilic charac-
ter,4a,b and hence, the formation of 3 can be explained
by assuming the initial formation of N-fluorosulfimides
2, which undergo 1,2-migration of the fluorine atom.
In order to verify the above proposed possibilities, we
carried out the reaction of sulfimides 1a, 1b, and 1d
with Selectfluor™ in CD3CN at −40°C. In the reaction
of 1a and 1b, the starting materials immediately disap-
peared, and the peaks due to fluoro-l6-sulfanenitriles 3a
and 3b appeared, while in the reaction of 1d the reac-
tion mixture showed the same peaks of the starting
materials in the 1H and 19F NMR spectrum. Up to
−20°C, the 19F NMR peak of Selectfluor™ at l 46.1
Further, the reaction of heterocyclic sulfimide, 10,10-
dioxo-5H-5l4,10l6-thianthren-5-ylideneamine (4)12 with
Selectfluor™ gave the corresponding fluoro-l6-sul-
fanenitrile 5 in 65% yield (Scheme 2).13 Interestingly,
this reaction should be applicable to the formation of
cyclic-fluoro-l6-sulfanenitriles, because the conversion
of cyclic-N-bromosulfimides with a fluoride anion to
the corresponding l6-sulfanenitriles is difficult. The new
cyclic-fluoro-l6-sulfanenitrile 5 was characterized by its
analytical and spectroscopic data.14 The molecular
structure of 5 was determined by X-ray crystallographic
analysis (Fig. 2).15 The thianthrene ring system is found
in the expected boat conformation. The S1ꢂN1 and
Figure 1. Calculated relative energies of 2A and 3A. (a)
B3LYP/6-311++G(3df,2pd)//B3LYP/6-31G(d), ZPE corrected
values (kcal/mol).
,
S1ꢂF1 bond lengths (1.435(2) and 1.584 (2) A) in 5 are
somewhat shorter than those of fluoro(4-nitro-
6
,
phenyl)(phenyl)-l -sulfanenitrile 3d (SꢂN; 1.444(2) A,
16
,
SꢂF; 1.638 (2) A).
In summary, we have demonstrated the formation of
acyclic and cyclic fluoro-l6-sulfanenitriles from the
reaction of the corresponding sulfimides with Selec-
tfluor™. Our current efforts include elucidation of the
mechanism for the migration of the fluorine atom and
application of this reaction system to the preparation of
other heterocyclic fluoro-l6-sulfanenitriles.
Scheme 2. (a) 4 (1 mmol), Selectfluor™ (0.5 mmol), CH3CN
(45 ml). (b) Isolated yields (based on Selectfluor™).
Acknowledgements
This work was partially supported by a Grants-in-Aid
for Research on Priority Areas (A) (No. 13029039 and
14044032) from the Ministry of Education, Culture,
Sports, Science and Technology.
Figure 2. The molecular structure of 5. Selected bond dis-
,
tances (A) and bond angles (°): S(1)ꢂF(1), 1.584(2); S(1)ꢂN(1),
1.435(2); S(1)ꢂC(1), 1.778(2), S(1)ꢂC(2), 1.780(2); S(2)ꢂO(1),
1.466(2); S(2)ꢂO(2), 1.434(2); S(2)ꢂC(3), 1.765(2); S(2)ꢂC(4);
1.771(2); F(1)ꢂS(1)ꢂN(1), 118.6(1), F(1)ꢂS(1)ꢂC(1), 99.98(9);
References
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116.5(1);
119.0(1);
105.25(9);
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3
,
102.850(9)°, U=1168.2(3) A , T=296 K, space group
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