3108
M. Sathe et al. / Tetrahedron Letters 47 (2006) 3107–3109
Table 1. Synthesis of phosphonates using silica chloride
geneous catalyst. The main advantage of this method
is that it requires mild reaction conditions, short reac-
tion times, takes place at ambient temperature with
operational simplicity and with excellent yields.
O
P
O
P
R'O
R'O
HO
HO
SiO2-Cl (1 mmol)
R
R
R'OH, 0 C 20-40 min
˚
R0
Yield (%)a
31P NMR (ppm)b
Acknowledgements
Entry
R
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
CH3
CH3
CH3
CH3
CH3
CH3
C2H5
C2H5
C2H5
C2H5
C2H5
n-C3H7
n-C3H7
n-C3H7
i-C3H7
i-C3H7
CH3
C2H5
89
88
80
92
90
90
94
90
92
89
91
89
88
90
92
90
32.3
30.1
29.8
27.8
28.9
29.2
33.3
33.9
32.8
32.1
32.6
32.6
32.2
29.2
32.6
30.2
We thank Shri K. Sekhar, Director DRDE, Gwalior for
his keen interest and encouragement.
n-C3H7
i-C3H7
n-C4H9
C6H11
CH3
References and notes
C2H5
1. Hinkle, P.; McCarty, R. Y. Sci. Am. 1978, 104, 238.
2. (a) Eto, M. Organophosphorus Pesticides: Organic and
Biological Chemistry; CRC Press: USA, 1974; p 18; (b)
Van Wazer John, R. In Phosphorus and its Compounds;
Interscience: New York, 1961; Vol. II; (c) Engel, R. Chem.
Rev. 1977, 77, 349.
3. Kosolapoff, G. M. In Organic Phosphorus Compounds;
Wiley-Interscience: New York, 1950; Vol. 6, p 503.
4. (a) Kafarski, P.; Lejczak, B. Phosphorus, Sulfur Silicon
Relat. Elem. 1991, 63, 193; (b) Shi, E.; Pei, C. Synthesis
2004, 2995.
n-C3H7
i-C3H7
n-C4H9
CH3
C2H5
n-C3H7
CH3
C6H5
All compounds were characterized by IR, NMR and MS.
a Isolated yield.
b 31P NMR spectra were recorded in CDCl3 at 400 MHz.
5. Krise, J. P.; Stella, V. J. Adv. Drug Delivery Rev. 1996, 19,
287.
6. Hildebrand, R. The Role of Phosphonates in Living
Systems; CRC Press: Boca Raton, 1983.
7. (a) Engel, R. Chem. Rev. 1977, 77, 349; (b) Whitehead, A.;
Moore, J. D.; Hanson, P. R. Tetrahedron Lett. 2003, 44,
4275.
8. (a) Hooijschuur, E. W. J. Trends Anal. Chem. 2002, 21,
116; (b) Mesilaakso, M.; Tolppa, E. L. Anal. Chem. 1996,
66, 2313; (c) Black, R. M.; Read, R. W. J. Chromatogr., A
1997, 759, 79; (d) Chemical Weapons Chemical Analysis;
Mesilaakso, M., Ed.; Encyclopedia of Analytical Chem-
istry; Wiley: New York, 2000.
9. (a) Krutysch, W.; Trap, R. F. A Commentary on CWC;
Martinus Nijhott: The Netherlands, 1994; (b) Convention
of Prohibition of the Development, Production, Stockpiling
and Use of Chemical Warfare and on Their Destruction; US
Control and Disarmament Agency: Washington, DC,
1993.
because of the bulkiness of the corresponding alcohol.
The applicability of this method was further extended
to the synthesis of phosphates from diaryl phosphoric
acids (Table 2).
It is likely that silica chloride acts as a source of acid,
which protonates the phosphonic/phosphoric acid fol-
lowed by attack of an alkoxide ion on the phosphorus
atom, which results in esterification of the correspond-
ing acids. The structures of the products were confirmed
on the basis of their spectral data (1H NMR, 31P NMR
and MS).19 The advantage of using silica chloride is that
it can be prepared from readily available material20 and
can also be removed easily from the reaction mixture.
10. (a) Bhattacharya, A. K.; Thyagarajan, G. Chem. Rev.
1981, 81, 415; (b) Michaelis, A.; Kaehne, R. Ber. Dtsch.
Chem. Ges. 1898, 31, 1048; (c) Arbusov, B. A. Pure Appl.
Chem. 1964, 9, 315.
In conclusion, an efficient and simple method for the
synthesis of alkyl/aryl phosphonates and phosphates
has been described using silica chloride as a hetero-
11. (a) Methoden der Organischen Chemie (Houben-Weyl);
Muller, E., Ed.; George Thieme: Stuttgart, 1964; Vol. XII/
I, p 433; (b) Michaelis, A.; Becker, T. Chem. Ber. 1897, 30,
1003.
12. (a) Nicolaou, K. C.; Yang, Z.; Ouellette, M.; Shi, G. O.;
Gaertner, P.; Gunzner, J. L.; Agrios, C.; Huber, R.;
Chadha, R.; Huang, D. H. J. Am. Chem. Soc. 1997, 119,
8105; (b) Dennis, E. A.; Westheimer, F. H. J. Am. Chem.
Soc. 1966, 88, 3432; (c) Poshkus, A. C.; Herweh, J. E. J.
Am. Chem. Soc. 1962, 84, 555.
Table 2. Synthesis of phosphates using silica chloride
O
P
O
P
C6H5O
C6H5O
SiO2-Cl (1 mmol)
OR'
OH
R'OH, 0 C 20-40 min
˚
C6H5O
C6H5O
Entry
R0
Yield (%)a
31P NMR (ppm)b
13. (a) Reactions and Methods of Organic Compound Investi-
gation; Kabachnik, M., Ed.; Goskhimizdat: Moscow,
1953; Vol. 13, p 427; (b) Grapov, A. F. Reakts. Metody
Issled. Org. Soedin. 1966, 15, 41.
14. Kosolapoff, G. M. J. Am. Chem. Soc. 1945, 67, 1180.
15. (a) McKillop, A.; Young, D. W. Synthesis 1979, 401; (b)
Cornelis, A.; Laszlo, P. Synthesis 1985, 909.
1
2
3
4
5
6
CH3
C2H5
n-C3H7
i-C3H7
n-C4H9
C6H11
89
88
90
92
90
95
ꢀ15.1
ꢀ15.4
ꢀ14.8
ꢀ14.5
ꢀ12.4
ꢀ12.2
All compounds were characterized by IR, NMR and MS.
16. (a) Tal, D. M.; Keinan, E.; Mazur, Y. Tetrahedron 1981,
37, 4327; (b) Onofrio, F. D.; Scettri, A. Synthesis 1985,
1159.
a Isolated yield.
b 31P NMR spectra were recorded in CDCl3 at 400 MHz.