1190
TOLSTIKOVA et al.
qualitatively similar to that of triphenylphosphine
CF3SO2N=S=O + PPh3 → CF3SO2N=PPh3 + SO.
II
(9)
oxide but the signals are shifted downfield by 0.10 (Но,
Нm) and 0.14 ppm (Нp) relative to the corresponding
signals of Ph3P=O. The signal in the 31Р NMR
spectrum is also shifted downfield relative to
triphenylphosphine by 26 ppm.
I
The reaction of compound I with triphenyl-
phosphine oxide in benzene also results in product II,
although the reaction proceeds much more slowly.
According to the 31Р NMR spectroscopy data, the
conversion of triphenylphosphine oxide after 2 h at 80°С
was as low as 7%.
The molecular ion peak is lacking in the mass
spectrum of compound II. The main fragment ion
[Ph3PNSO2]+ with m/z 340 corresponds to elimination
of CF3 from the molecular ion. Similar fragmentation
is characteristic of trifluoro-N-(trichloro-λ5-phosphanyl-
idene)methanesulfonamide CF3SO2N=PCl3 [8].
(10)
CF3SO2N=S=O + O=PPh3
CF3SO2N=PPh3.
–SO2
I
II
We believe that the reasons for a substantially
lower activity of triphenylphosphine oxide as
compared to triphenylphosphine in the reaction with
compound I are similar to those in the reaction of
oxidation of sulfides into sulfoxides and of sulfoxides
into sulfones as we have considered earlier [7]. Reac-
tion (9) consists in a nucleophilic attack of the lone
pair of the phosphorus atom in Ph3P on the electron-
After staying in the solution, new signals of a minor
product appear in the NMR spectra of product II, as
shown in the figure by the example of the 13С NMR
spectrum.
Complete resemblance of the 13С NMR spectra is
indicative of the presence of the same groups in the
formed product as in compound II, that is, Ph3P and
NSO2CF3. In the 31Р NMR spectrum, two signals at 52
(minor) and 21 ppm are observed, and the JCP constants
in the 31Р NMR spectrum measured for these signals
from 13С satellites coincide with the JCP constants in the
13С NMR spectrum for the Ci carbon signals in the minor
product and in compound II, respectively. In the 19F
NMR spectrum two signals are present at –78.45 ppm
deficient nitrogen atom in TfN+–S=O; similar to that
–
the oxidation of sulfides is a nucleophilic attack of the
lone pair (LP) of the sulfur atom on the oxygen atom
of the oxidant. On the contrary, reaction (10) is a
nucleophilic attack of the nitrogen LP in compound I
on the electrophilic phosphorus atom of Ph3P=O, like
the oxidation of sulfoxides consists in a nucleophilic
attack of the oxidant on the sulfur atom in R2SO. Ex-
tremely low basicity of nitrogen atom in compound I
results in the low reactivity of triphenylphosphine oxide.
1
(minor) and –79.34 ppm (major). In the Н NMR
spectrum, apart from the signals of aromatic protons, a
downfield signal appears at 11.5 ppm. The similarity
of the 13С NMR spectra and substantial difference of
the 31Р chemical shifts, as well as almost complete
coincidence of the minor 19F signal with that of
triflamide (–78.52 ppm) allow to conclude that the
minor product is the product of hydration of trifluoro-
N-(triphenyl-λ5-phosphanylidene)methanesulfonamide
(II), trifluoro-N-[hydroxy(triphenyl)phosphoranyl]-
methanesulfonamide (IV), which is the intermediate
product of hydrolysis before the formation of tri-
flamide and triphenylphosphine oxide.
Product II was independently synthesized by the
reaction of N-trifluoromethanesulfonamide CF3SO2·
NH2 III with dichloro(triphenyl)phosphorane prepared
in situ by the chlorination of triphenylphosphine with
phosphorus pentachloride.
(11)
CF3SO2NH2 + PPh3Cl2
CF3SO2N=PPh3.
–HCl
III
II
The structure of product II was proved by the
presence of doublet signals of the Со, Сm, Сp carbon
atoms split by coupling with the phosphorus atom in
the 13С NMR spectrum and a quartet of doublets of the
CF3 group. A specific difference of the 13С NMR
spectra of compound II and triphenylphosphine oxide
is that in Ph3PO the Сi atom gives the most downfield
signal (133 ppm), while in product II it is the most
upfield signal of the phenyl group (126 ppm). In the 1Н
NMR spectrum of product II the signals of the Но, Нm,
Нp protons are separated, in contrast to the PPh3
spectrum where they all resonate as a singlet at 7.36
ppm. The 1Н NMR spectrum of product II is
H2O
CF3SO2N=PPh3
CF3SO2NH–PPh3
OH
II
IV
(12)
CF3SO2NH2 + O=PPh3.
III
Therefore, the reaction of N-sulfinyltrifluorometh-
anesulfonamide with triphenylphosphine and tri-
phenylphosphine oxide, as well as the reaction of tri-
fluoromethanesulfonamide with dichloro(triphenyl)-
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 80 No. 6 2010