2,5-diphenyl-1,4-(trifl uoromethylsulfonyl)piperazine from N-(2-bromo-2-phenylethyl)trifluoromethanesulfonamide

Full text of DOI:10.1134/S1070428010110229

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2010, Vol. 46, No. 11, pp. 1743−1744. © Pleiades Publishing, Ltd., 2010.
Original Russian Text © B.A. Shainyan, I.V. Sterkhova, 2010, published in Zhurnal Organicheskoi Khimii, 2010, Vol. 46, No. 11, pp. 1732−1733.
SHORT
COMMUNICATIONS
2,5-Diphenyl-1,4-(trifluoromethylsulfonyl)piperazine
from N-(2-bromo-2-phenylethyl)trifluoromethanesulfonamide
B. A. Shainyan and I. V. Sterkhova
Faworsky Irkutsk Institute of Chemistry, Siberian Branch, Russian Academy of Sciences, Irkutsk, 664033 Russia
e-mail: bagrat@irioch.irk.ru
Received March 30, 2010
DOI: 10.1134/S1070428010110229
Aiming at preparation of unsaturated derivatives
of trifluoromethanesulfonamide containing a fragment
CF3SO2NHCH=CH– we synthesized by the bromina-
tion of N-(2-phenylethyl)trifluoromethanesulfonamide
(I) N-(2-bromo-2-phenylethyl)trifluoromethanesulfon-
amide (II) and carried out the dehydrobromination of
compound II with triethylamine. It turned out unexpect-
edly that the reaction product was 2,5-diphenyl-1,4-
(trifluoromethylsulfonyl)piperazine (III). By the 1H and
13C NMR data and the melting point compound III was
identical to the substance that we had obtained by the
styrene reaction with trifluoromethylsulfonylnitrene and
whose structure we had established with the use of XRD
analysis [1] (Scheme 1).
1
As showed the H and 13C NMR data the expected
N-(2-phenylethenyl)trifluoromethanesulfonamide
CF3SO2NHCH=CHPh or its tautomer N-(2-phenyl-
ethylidene)trifluoromethanesulfonamideC F3SO2N=
=CHCH2Ph were lacking in the reaction mixture.
Evidently due to the high NH-acidity of compound II
first the treatment with the triethylamine generated the
amide anion IV, then the substitution occurs of bromide
Scheme 1.
CF3SO2F + H2NCH2CH2Ph
CF3SO2NHCH2CH2Ph
I
Ph
Br2, hv, CCl4
Et3N
_HBr
CF3SO2N
Ph
NSO2CF3
CF3SO2NHCH2CHBrPh
II
_HBr
III
Scheme 2.
_
+
Et3NH + CF3SO2NCH2CHBrPh
IV
CF3SO2NHCH2CHBrPh + Et3N
II
CF3SO2NHCH2CHBrPh
+
Et3NH Br
_
CH2CHBrPh
IV
CH2CH(Ph)
CF3SO2N
III
CF3SO2N
_
CH(Ph)CH2NHSO2CF3
II
CHCH2NSO2CF3
+
Et3NH Br
1743

SHAINYAN, STERKHOVA
1744
in the second molecule II with electrophilic assistance
of the triethylammonium cation.
Found, %: C 31.98; H 2.72; Br 24.61; F 17.21; N 4.23;
S 9.23. C9H9BrF3NO2S. Calculated, %: C 32.55; H 2.73;
Br 24.06; F 17.16; N 4.22; S 9.65.
N-(2-Phenylethyl)trifluoromethanesulfonamide
(I). A mixture of 1.0 ml (0.12 mol) trifluoromethane-
sulfonyl fluoride CF3SO2F frozen with liquid nitrogen
and 50 ml (0.47 mol) of 2-phenylethylamine was placed
into a pressure reactor and heated for 12 h at 70–80°C,
then cooled with liquid nitrogen, the reactor was opened,
the formed thick syrupy mass was diluted with water,
acidified with HCl (overall volume 400 ml), strirred for
2 h, and extracted with ethyl ether. The extract was dried
with MgSO4, the solvent was distilled off, the residue
was distilled in a vacuum. Yield 16.5 g (53%), bp 106°C
(2 mm Hg). IR spectrum, ν, cm–1: 3320 (NH), 1604,
1455, 1373, 1232, 1198, 1147, 1071, 701, 610. 1H NMR
spectrum (CDCl3), δ, ppm: 2.83 m (2H, CH2Ph), 3.38 m
(2H, CH2N), 7.25 m (5H, Ph), 9.44 m (1H, NH). 13C NMR
spectrum (CDCl3), δ, ppm: 35.95 (CPh), 44.83 (NC),
119.85 q (CF3, JCF 322.4 Hz), 126.50 (Cp), 128.42 (Cm),
128.83 (Co), 137.91 (C1). 19F NMR spectrum (CDCl3),
δ, ppm: –77.76. Found, %: C 42.19; H 3.98; F 23.33;
N 6.62; S 12.78. C9H10F3NO2S. Calculated, %: C 42.69;
H 3.98; F 22.51; N 5.53; S 12.66.
2,5-Diphenyl-1,4-(trifluoromethylsulfonyl)pipera-
zine (III). A solution of 5 g (15 mmol) of compound II
and 15 ml (0.1 mol) of triethylamine in 50 ml of CCl4
was heated under reflux for 2 h, the solvent and excess
triethylamine was distilled off, the residue was dried
and subjected to column chromatography on silica gel,
eluents hexane, hexane–ethyl ether, 1 : 2, ethyl ether,
methanol. Yield 0.65 g (9%). Colorless crystals, mp
128°C. IR spectrum, ν, cm–1: 1403, 1229, 1202, 1122,
1028, 956, 876, 759, 742, 699, 611, 498. 1H NMR spec-
trum (CD3CN), δ, ppm: 4.01 d.d [1H, 3(6)-Htrans, J 15.2,
11.4 Hz], 4.40 d.d [1H, 3(6)-Hcis, J 15.6, 6.7 Hz], 5.32 d.d
[1H, 2(5)-H, J 10.8, 6.8 Hz], 7.46 m (5H, Ph). 13C NMR
spectrum (CD3CN), δ, ppm: 48.63 (CH2), 61.66 (CH),
120.47 q (CF3, JCF 321.0 Hz), 127.50 (Co), 129.99 (Cm),
130.17 (Cp), 137.74 (C1). 19F NMR spectrum (CD3CN),
δ, ppm: –77.34.
IR spectra were recorded on a spectrophotometer
Bruker Vertex 70 from thin film or pellets with KBr.
NMR spectra were registered on a spectrometer Bruker
DPX 400 at operating frequencies 400 (1H), 100 (13C),
386 MHz (19F), chemical shifts are reported with respect
to TMS (1H, 13C) and CCl3F (19F).
N-(2-Bromo-2-phenylethyl)trifluoromethanesul-
fonamide (II). To a solution of 3.8 g (15 mmol) of com-
pound I in 25 ml of CCl4 was added dropwise 1 ml (3.1 g,
19 mmol) of Br2 over 3 h while stirring and irradiation
with an UV lamp. The residue after evaporation of the
solvent was dried in a deep vacuum. Yield 5 g (98%).
IR spectrum, ν, cm–1: 3313 (NH), 1601, 1429, 1377,
ACKNOWLEDGMENTS
The study was carried out under a financial support
from the Russian Foundation for Basic Research (grant
no.10-03-00110).
1
1234, 1199, 1145, 1073, 699, 610. H NMR spectrum
(CDCl3), δ, ppm: 3.87 m (2H, CH2N), 5.04 d.d (1H,
CHBr, J 8.1, 6.6 Hz), 5.39 уш.t (1H, NH, J 6.0 Hz),
7.41 m (5H, Ph). 13C NMR spectrum (CDCl3), δ, ppm:
50.98 (CHBr), 52.38 (CH2), 119.57 q (CF3, JCF 32.8 Hz),
127.69 (Cm), 129.34 (Co), 129.66 (Cp), 140.52 (C1).
REFERENCES
1. Shainyan B.A., Moskalik M.Yu., Starke I., and Schilde U., Tet-
rahedron, 2010, vol. 66, p. 8383.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 46 No. 11 2010