Rapid and high yield oxidation of phosphine, phosphite and phosphinite compounds to phosphine oxides, phosphates and phosphinates using hypofluorous acid-acetonitrile complex

Article abstract of DOI:10.1016/j.jfluchem.2005.02.012

The hypofluorous acid acetonitrile complex was used as a mild, rapid, and effective agent to oxidize a wide variety of phosphines, phosphites and phosphinites to the corresponding phosphine oxide, phosphate and phosphinate compounds.

Full text of DOI:10.1016/j.jfluchem.2005.02.012

Journal of Fluorine Chemistry 126 (2005) 1054–1056
www.elsevier.com/locate/fluor
Rapid and high yield oxidation of phosphine, phosphite and
phosphinite compounds to phosphine oxides, phosphates and
phosphinates using hypofluorous acid–acetonitrile complex
*
Weimin Peng, Jean’ne M. Shreeve
Department of Chemistry, University of Idaho, Moscow, ID 83844-2343, USA
Received 17 February 2005; accepted 26 February 2005
Available online 13 April 2005
Dedicated to Professor Herbert W. Roesky on the occasion of his 70th birthday.
Abstract
The hypofluorous acid acetonitrile complex was used as a mild, rapid, and effective agent to oxidize a wide variety of phosphines,
phosphites and phosphinites to the corresponding phosphine oxide, phosphate and phosphinate compounds.
# 2005 Elsevier B.V. All rights reserved.
Keywords: Hypofluorous acid; Acetonitrile complex; Organophosphorus compounds; Oxidation
1. Introduction
Rozen and his group have introduced the HOFÁCH3CN
complex as a potent oxygen-transfer reagent for a variety of
reactions. They applied this reagent in the synthesis of
epoxides from various olefins, ketones from methyl ethers,
esters by the Baeyer–Villiger reaction, sulfones from
sulfides, nitro compounds from amines, amino acids, and
azides, N-oxides from tertiary amines, and other conversions
[12]. In the course of using HOFÁCH3CN complex to oxidize
some azido compounds for the synthesis of some novel high
energy nitro compounds, we found that the HOFÁCH3CN
complex could also be employed as a very mild, rapid,
efficient oxidizing agent to transform trivalent phosphorus
compounds to the corresponding phosphorus(V) oxides in
high yields.
Tertiary organophosphorus compounds are essentially
oxygen insensitive and air-stable both in the solid state and
when dissolved in common organic solvents. In the presence
of a catalytic amount of Co(acac)2 [1], P4O10 [2], tin(IV)
iodide [3], or other complexes [4], oxidation of alkyl and
aryl phosphines, phosphites and phosphinites can be
achieved using O2 or air as oxidant. Although these P(III)
derivatives could also be oxidized to P(V) compounds by
H2O2 or halogen (followed by hydrolysis), the former
procedure is hazardous, because some of the H2O2, which
may cocrystallize with the phosphine oxide during
recrystallization purification, remains in the product [5],
and the latter procedure does not give a pure product [6].
There are other methods for oxidation of tricoordinate
phosphorus compounds to phosphoric products using special
oxidizers such as aqueous NaOCl [7], Me2SO catalyzed by
MoO2Cl2[Me2SO)2] [8], ozone [9–10], and potassium
peroxymonosulfate (Oxone1) [11].
2. Results and discussion
A standard procedure for producing hypofluorous acid–
acetonitrile complex and using this complex to oxidize
trivalent phosphorus compounds was followed. A commer-
cially available premixed fluorine/nitrogen mixture (15%)
was bubbled through a porous finely sintered glass bubbler
* Corresponding author. Tel.: +1 208 885 6215; fax: +1 208 885 9146.
E-mail address: jshreeve@uidaho.edu (J.M. Shreeve).
0022-1139/$ – see front matter # 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.jfluchem.2005.02.012

W. Peng, J.M. Shreeve / Journal of Fluorine Chemistry 126 (2005) 1054–1056
1055
into a cold (À10 8C) mixture of 60 mL of CH3CN and 6 mL
of H2O for 3–4 h. The oxidizing power was monitored by
reacting aliquots with acidic aqueous solution of KI
followed by titration of the liberated iodine with dilute
sodium thiosulfate solution. Typical concentrations of the
oxidizing reagent were found to be around 0.05–0.1 M. The
phosphorus(III) compound 1 (2 mmol) was dissolved in
about 5 mL of CH2Cl2, and cooled to 0 8C. Then the
previously prepared HOFÁCH3CN solution (4 mmol) was
added in one portion to the above reaction mixture. After
vigorous stirring at 0 8C for ꢀ5 min, the reaction was
quenched with sufficient saturated sodium bicarbonate
solution to cause the reaction mixture to become basic. It
was then extracted with CH2Cl2 (3 Â 30 mL). The extracts
were washed with saturated NaCl solution (40 mL) and
dried over Na2SO4. Evaporation of the solvent left the
virtually pure (1H NMR and 31P NMR) phosphorus(V)
compound 2. The product may be further purified by
distillation in vacuo or by recrystallization. Their spectral
properties agree with literature values (Scheme 1).
Scheme 1.
96 kJ molÀ1) [13], the reactions described here are very
clean and no fluorine containing by-product was found.
However, the trialkyl phosphites [P(OR)3, R = Et or n-
Bu] gave phosphates in moderate yield because the
substrates underwent competitive hydrolysis reactions in
the acidic reaction medium to give H(O)P(OR)2, also [11].
Tetraethyl pyrophosphite underwent hydrolysis completely
to give H(O)P(OEt)2 and failed to give the corresponding
oxide. The phosphorus compounds subjected to HOF
oxidation are displayed in Table 1.
Although we have not tried, 18O isotope labeled
phosphate, which is very useful molecular probe in
biochemistry, could be conveniently obtained by this
method if H218O instead of the normal water was used in
the course of preparing the HOFÁCH3CN complex [19].
Premixed fluorine/nitrogen mixtures are commercially
Under the above conditions, P(III) compounds can be
oxidized in ꢀ5 min to provide the corresponding P(V)
derivatives generally in very high yields. Although fluorine
forms very strong bonds with phosphorus (439 Æ
Table 1
Substrate
31P NMR d (ppm)
Product
31P NMR d (ppm)
m.p. (8C)
Yield (%)
Found
Reported
Ph3P
À6.0 (CD2Cl2)a
À22.1
Ph3P
O
29.2
24.7
152–154
181–183
153–156b
181–183c
ꢀ100
ꢀ100
À13.0 (CD2Cl2)a
32.7
30.4
257–259
133–135
264–266d
95
Ph2POPh
111.0
137–138e
84
P(OPh)3
128.2
126.6
O
O
P(OPh)3
À17.5
49–50
47–49f
91
75g,h
Ph2POCH2CF3
35.2
–
–
P(OEt)3
140.1i
P(OEt)3
À0.8
8.0
–
–
–
–
–
–
–
–
–
–
47h
j
H(O)P(OEt)2
H(O)P(OEt)2
–
j
–
(EtO)2P–O–P(OEt)2
P(OBu-n)
128.9
139.3
8.0
O
P(OBu-n)3
À0.5
7.8
40k
50k
H(O)P(OBu-n)2
a
Ref. [3].
b
Ref. [14].
c
Ref. [15].
d
Ref. [16].
e
Ref. [17].
f
Ref. [18].
Ph2POCH2CF3: 31P NMR d 126.6 (q, J = 5.8 Hz); 1H NMR d 4.19 (quint, 2H, J = 8.5 Hz), 7.40–7.55 (m, 10H); 19F NMR d À74.9 (td, J = 8.5, 5.8 Hz).
g
Ph2P(O)OCH2CF3: 31P NMR d35.1; 1H NMR d 4.35 (qd, 2H, J = 8.2, 6.8 Hz), 7.49–7.87 (m, 10H); 19F NMR d À74.7 (t, J = 8.2 Hz).
h
The product is pure enough for characterization without purification.
i
Ref. [11].
j
The hydrolysis product was dissolved in the aqueous phase and could not be extracted with CH2Cl2.
k
The two products were separated by vacuum distillation.

1056
W. Peng, J.M. Shreeve / Journal of Fluorine Chemistry 126 (2005) 1054–1056
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142–149.
available and the work with it is as easy as turning a valve on
and off. The method of preparing the HOFÁCH3CN complex
is well-established, and all reaction vessels are standard
glassware. This conversion requires very mild conditions
and a very short time, thus the HOFÁCH3CN complex offers
a straightforward and expedient tool for the transformation
of P(III) derivatives to the P(V) products.
[7] T.O. Antoni, P.O. Oriol, B.L. Joaquin, G.G. Rosa, ES 2035789, 1993
(Chem. Abstr. 119 (1993) 226198).
[8] F.J. Arnaiz, R. Aguado, M.R. Pedrosa, A.D. Cian, Inorg. Chim. Acta
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tions see;
Acknowledgements
We are grateful to the National Science Foundation
(CHE-0315275), the Office of Naval Research (N00014-02-
1-0600) and the Air Force Office of Scientific Research
(F49620-03-1-0209) for support of this work.
S. Rozen, M. Carmeli, J. Am. Chem. Soc. 125 (2003) 8118–8119;
G.K.S. Prakash, M. Etzkorn, Angew. Chem. Int. Ed. 43 (2004) 26–
28;
E. Golan, A. Hagooly, S. Rozen, Tetrahedron Lett. 45 (2004) 3397–
3399;
M. Carmeli, S. Rozen, J. Org. Chem. 70 (2005) 2131–2134, and
references therein.
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