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Russ.Chem.Bull., Int.Ed., Vol. 59, No. 5, May, 2010
Gololobov et al.
Synthesis of phosphorus acid fluorides 3a,b. A. A solution
of CH acid 1a—c (0.5 mmol), 1ꢀfluoroꢀ2,4,6ꢀtrinitrobenzene
(1 mmol) and triethylamine (1 mmol) in THF (5 mL) was kept
at room temperature for 24 h. After mixing of the reactants, an
intensive darkꢀcherry color of the mixture was observed. In the
NMR spectra of all reaction mixtures, the signals characteristic
of phosphoryl fluorides were observed.
Diphenylphosphinic fluoride (3a). 31P NMR, δ: 39.25,
JP,F = 1015 Hz; 19F NMR, δ: 73.29, JF,P = 1015 Hz (cf. Ref 6:
31P NMR: 40.5 ppm, JP,F = 1010 Hz; 19F NMR, δ: 11.6 (relative
to PhCF3), JF,P = 1010 Hz).
OꢀEthyl PꢀphenylꢀPꢀfluorophosphinate (3b). 31P NMR, δ:
16.94, JP,F = 1032 Hz; 19F NMR, δ: 63.52, JF,P = 1036 Hz
(cf. Ref 6: 31P NMR, δ: 16.3, JP,F = 1035 Hz; 19F NMR, δ: 63.8
(relative to PhCF3), JF,P = 1010 Hz).
B. To a solution (or suspension) of CH acid 1a—c
(0.5 mmol) in THF (5 mL), equimolar amount of NaH (60%
dispersion in mineral oil) was added. To the resulting homoꢀ
genous mixture, a solution of 1ꢀfluoroꢀ2,4,6ꢀtrinitrobenzene
(0.5 mmol) in THF (2—3 mL) was added. Immediately, the
darkꢀred color of the mixture appeared. The reaction mixture
was kept at room temperature for 24 h. The 19F and 31P NMR
spectra of the resulting reaction mixtures were similar to that
obtained by the method A.
compounds of unknown structure. In this case the P—F
bond formation mechanism is probably similar to that of
the P—C bond cleavage in the Horner—Wadsworth—
Emmons reaction,1 which is known to involve an intraꢀ
molecular attack of the phosphorus atom by the negaꢀ
tively charged oxygen atom of the carbonyl counterpart.
In our case, intramolecular attack of the phosphorus atom
by the fluorine atom of the σFꢀcomplex 2 occurred. The
possibility of the cleavage of the P—C bond under the
action of the fluoride ion is documented.2
The structures of fluorides 3 were confirmed by 19F
and 31P NMR spectroscopy. In the 19F and 31P NMR
spectra of the reaction mixtures, the doublets with the
1
spinꢀspin coupling constants JP,F of ~1000 Hz were
observed. Compounds 3a,b were isolated in the yields
of ~50%. The chemical shifts for the phosphorus atom
and observed coupling constants values are consistent with
the published data on the resulting phosphorus acid
fluorides.
One of the driving forces of the P—C bond cleavage,
which proceeds so readily, is obviously a gain in the
energy due to the bond P—F (E = 126 kcal mol–1) formaꢀ
tion, which is more energetically favorable in respect of
the P—C bond (E = 65 kcal mol–1).
This work was financially supported by the Russian
Foundation for Basic Research (Grant No. 08ꢀ03ꢀ00196a).
The scope of the reactions under study is obviously
defined by the CH acidity of the starting compounds bearꢀ
ing an active methylene group as well as the steric factors
(a certain steric accessibility is required for the effective
attack of the carbanion by 1ꢀfluoroꢀ2,4,6ꢀtrinitrobenzene).
These issues and the nature of the resulting compounds
as well will be covered later.
The reaction under consideration is of low synthetic
interest as the phosphoryl fluorides can easily be prepared
from the corresponding chlorides. However, this reaction
is of importance for the understanding of the chemical
properties of αꢀphosphorusꢀcontaining CH acids. The
latter are of considerable interest as pharmaceuticals,
extractants and complexing agents and for the synthesis
of practically useful compounds as well.3
References
1. W. S. Wadsworth, Organic Reactions, 25, 1977, 73.
2. G. A. Artamkina, E. A. Tarasenko, N. V. Lukashev, I. P.
Beletskaya, Tetrahedron Lett., 1998, 39, 901.
3. L. D. Quin, A guide to Organophosphorus Chemistry, John
Wiley and Sons, Inc. Publication, New York, 2000, 394.
4. A. N. Pudovik, G. E. Yastrebova, L. M. Leont´eva, T. A.
Zyablikova, V. I. Nikitina, Zh. Obshch. Khim., 1969, 39,
1230 [J. Gen. Chem. USSR (Engl. Transl.), 1969, 39].
5. E. S. Petrov, E. N. Tsvetkov, M. I. Terekhova, P. A.
Malevannaya, A. I. Shatenshtein, M. I. Kabachnik, Izv.
Akad. Nauk SSSR, Ser. Khim., 1976, 534 [Bull. Acad. Sci.
USSR, Div. Chem. Sci. (Engl. Transl.), 1976, 25, 517].
6. R. Schmutzler, J. Chem. Soc., 1964, 4551.
The 19F and 31P NMR spectra were recorded on a Bruker
AMXꢀ300 instrument at 282.4 MHz and 121.5 MHz, respecꢀ
tively. All reactions were carried out under dry nitrogen. Solvents
were purified and dried prior to use. Starting compounds 1a—c
were synthesized by the known procedures,4—5 their physicoꢀ
chemical characteristics coincided with published data.
Received July, 2009;
in revised form December, 28 2009
Gololobov
