N-Methyl-N-(2-phenylethenyl)trifluoromethanesulfonamide

Full text of DOI:10.1134/S107042801201023X

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2012, Vol. 48, No. 1, pp. 141–142. © Pleiades Publishing, Ltd., 2012.
Original Russian Text © B.A. Shainyan, I.V. Ushakova, 2012, published in Zhurnal Organicheskoi Khimii, 2012, Vol. 48, No. 1, pp. 145–146.
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N-Methyl-N-(2-phenylethenyl)trifluoromethanesulfonamide
B. A. Shainyan and I. V. Ushakova
Favorskii Irkutsk Institute of Chemistry, Siberian Division, Russian Academy of Sciences,
ul. Favorskogo 1, Irkutsk, 664033 Russia
e-mail: bagrat@irioch.irk.ru
Received June 21, 2011
DOI: 10.1134/S107042801201023X
There are only a few published data on N-alkenyl-
substituted sulfonamides of the general formula
R1SO2N(R2)–C(R3)=CR4R5. Hydrostannylation of
N-tosyl-substituted ynamines TsN(Bzl)C≡CSiMe3 [1]
and TsN(Bzl)C≡CH [2] led to the corresponding
N-tosyl enamines TsN(Bzl)C(SnBu3)=CHSiMe3 [1]
and TsN(Bzl)C(SnBu3)=CH2, and coupling of the latter
with various organic halogen compounds RX afforded
N-benzyl-N-(1-R-vinyl)-p-toluenesulfonamides
TsN(Bzl)C(R)=CH2; N-alkenylsultams were synthe-
sized from N-alkynyl precursors [3]. Unsaturated
derivatives of trifluoromethanesulfonamide containing
a CF3SO2N(R)CH=CHR′ fragment were not reported
so far. With a view to obtain N-(2-phenylethenyl)-
trifluoromethanesulfonamide CF3SO2NHCH=CHPh
we previously synthesized N-(2-phenylethyl)trifluoro-
methanesulfonamide whose bromination gave
N-(2-bromo-2-phenylethyl)trifluoromethanesulfon-
amide, and the latter was subjected to dehydrobromi-
nation by the action of triethylamine [4]. Unexpect-
edly, the product of this reaction was 2,5-diphenyl-1,4-
bis(trifluoromethylsulfonyl)piperazine (Scheme 1); its
initial trifluoromethanesulfonamide contains an NH
proton. To rule out this possibility N-(2-phenylethyl)-
trifluoromethanesulfonamide (I) was preliminarily
subjected to methylation with methyl iodide. N-Meth-
yl-N-(2-phenylethyl)trifluoromethanesulfonamide (II)
thus formed was brominated to N-(2-bromo-2-phenyl-
ethyl)-N-methyltrifluoromethanesulfonamide (III), and
dehydrobromination of the latter with alcoholic alkali
afforded N-methyl-N-[(E)-2-phenylethenyl]trifluoro-
methanesulfonamide (IV) (Scheme 2) as the first re-
presentative of N-alkenyl-substituted trifluoromethane-
sulfonamide derivatives.
Scheme 2.
MeI
CF3SO2NHCH2CH2Ph
CF3SO2N(Me)CH2CH2Ph
–HI
I
II
Br2
CF3SO2N(Me)CH2CHBrPh
–HBr
III
Me
N
KOH
–HBr
13
1H and C NMR spectra and melting point were iden-
CF3SO2
Ph
IV
tical to those of a sample synthesized by us previously
from styrene and trifluoromethanesulfonamide (its
structure was proved by X-ray analysis [5]).
According to the NMR data, the reaction was not
accompanied by side processes. The purity of inter-
1
mediate products II and III was checked by H NMR
Scheme 1.
spectroscopy, and the structure of compound IV was
Et3N
SO2CF3
1
confirmed by its H, 13C, and 19F NMR spectra and
CF3SO2NHCH2CHBrPh
–HBr
Ph
N
elemental analysis. trans Configuration of the double
bond in molecule IV followed from the coupling con-
3
1
stant JHH = 14.4 Hz. By comparing the H and 13C
NMR spectra of compound IV and styrene the follow-
ing substituent shielding constants of the N-methyltri-
fluoromethanesulfonamide moiety CF3SO2N(Me) for
olefinic protons and carbons were determined:
N
Ph
PhCH=CH2
+ CF3SO2NH2
SO2CF3
Obviously, dehydrohalogenation may be accom-
panied by heterocyclization process only when the
141

SHAINYAN, USHAKOVA
142
1H NMR: σgem = 1.35, σcis = –0.3 ppm; 13C NMR: σα =
10.7, σβ = –20.8 ppm; signals were assigned using the
1H–13C HSQC and HMBC techniques.
N-Methyl-N-[(E)-2-phenylethenyl]trifluoro-
methanesulfonamide (IV). Compound III, 0.83 g
(2.4 mmol), was added dropwise over a period of 1 h
under stirring to a solution of 0.39 g (7 mmol) of
potassium hydroxide in 10 ml of anhydrous methanol.
The product was isolated by vacuum distillation. Yield
N-Methyl-N-(2-phenylethyl)trifluoromethanesul-
fonamide (II). Methyl iodide, 1.86 ml (0.03 mol), was
added dropwise to a mixture of 2.53 g (0.01 mol) of
N-(2-phenylethyl)trifluoromethanesulfonamide (I)
(prepared according to [4]), 10 ml of N,N-dimethyl-
formamide, and 5.5 g (0.04 mol) of potassium car-
bonate, the mixture was stirred for 2 h at 25°C, the
precipitate was filtered off and washed with a small
amount of DMF, the filtrate was evaporated, and the
residue was distilled under reduced pressure. Yield
1
49%, bp 80–82°C (0.5 mm). H NMR spectrum
(DMSO-d6), δ, ppm: 3.34 s (3H, NCH3), 6.43 d (1H,
PhCH=, J = 14.4 Hz), 7.17 d (1H, NCH=, J =
14.4 Hz), 7.22 t (1H, p-H, J = 7.3 Hz), 7.31 t (2H,
m-H, J = 7.5 Hz), 7.41 d (2H, o-H, J = 7.5 Hz).
13C NMR spectrum (DMSO-d6), δC, ppm: 34.21
(NCH3), 115.87 (PhCH=), 119.48 q (CF3, JCF
=
325.5 Hz), 124.82 (NCH=), 125.90 (Cm), 127.33 (Cp),
128.72 (Co), 134.66 (Ci). 19F NMR spectrum (CDCl3):
δF –74.43 ppm. Found, %: C 44.98; H 3.06; N 5.13;
S 11.50. C10H10F3NO2S. Calculated, %: C 45.28;
H 3.80; N 5.28; S 12.09.
1
75%, bp 102°C (0.5 mm). H NMR spectrum
(DMSO-d6), δ, ppm: 2.98 t (2H, PhCH2, J = 7.6 Hz),
3.03 s (3H, NCH3), 3.60 br.s (2H, NCH2), 7.25 m (2H,
m-H), 7.30 m (1H, p-H), 7.36 m (2H, o-H). 13C NMR
spectrum (CDCl3), δC, ppm: 34.87 (PhCH2), 35.58
(NCH3), 52.40 (NCH2), 120.16 q (CF3, JCF = 323.8 Hz),
126.90 (Cp), 128.70 (Cm), 128.72 (Co), 137.02 (Ci).
19F NMR spectrum (CDCl3): δF –75.29 ppm.
The NMR spectra were recorded on a Bruker DPX
400 spectrometer at 400 (1H), 100 (13C), or 386 MHz
(19F); the chemical shifts are given relative to tetra-
methylsilane (1H, 13C) or CCl3F (19F).
N-(2-Bromo-2-phenylethyl)-N-(methyl)trifluoro-
methanesulfonamide (III). Compound II, 1.6 g
(6 mmol), was dissolved in 10 ml of carbon tetra-
chloride, and 0.5 ml (0.01 mol) of bromine was added
dropwise over a period of 3 h under stirring and UV
irradiation. The product was isolated by vacuum dis-
tillation. Yield 59%, bp 92°C (0.5 mm). 1H NMR spec-
trum (DMSO-d6), δ, ppm: 3.01 s (3H, NCH3), 3.99 br.s
(1H, NCH2), 4.10 d.d (1H, NCH2, J = 14.0, 8.0 Hz),
5.53 t (1H, CHBr, J = 7.6 Hz), 7.39 m (3H, m-H, p-H),
7.55 d (2H, o-H, J = 7.1 Hz). 13C NMR spectrum
(DMSO-d6), δC, ppm: 35.54 (NCH3), 50.26 (NCH2),
56.01 (CHBr), 119.73 q (CF3, JCF = 324.7 Hz), 128.09
(Co), 128.76 (Cm), 129.08 (Cp), 138.05 (Ci). 19F NMR
spectrum (CDCl3): δF –76.03 ppm.
This study was performed under financial support
by the Russian Foundation for Basic Research (project
no. 10-03-00110).
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RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 48 No. 1 2012