A general synthesis of phosphonic acid dichlorides using oxalyl chloride and DMF catalysis

Article abstract of DOI:10.1016/S0040-4039(00)60798-0

A general synthesis of phosphonic diacid dichlorides (1) using oxalyl chloride and catalytic DMF is described.

Full text of DOI:10.1016/S0040-4039(00)60798-0

vol. 33. No. 49. pp.
Printed in Groat Britain
00404039~2
+
Synthesis of
Acid Dichlorides
using
General
Chloride and
Catalysis
Roland S. Rogers
Chemical Sciences Department, Monsanto
Research
Monsanto Company, 800 N. Lindbergh Blvd. St Louis. MO. 63167
A
of
(1) using oxalyl
and catalytic DMF is described.
There are scattered reports in the literature of the synthesis of phosphorous acid chlorides. Those which
thionyl chloride2 as the
and ethyl or methylchloride are troublesome side products generated
under these conditions, and these reactions suffer from variable yields. Other first converted
phosphorous diesters into diesters before reaction with phosphorous pentachloride or oxalyl chloride.
In addition to the extra chemical transformation required. one now has a volatile silyl chloride as a side product,
which is problematic on large scale. A third approach has been the direct of phosphonic acids to
phosphonic dichlorides. Again, phosphorous has been widely used, but again, the yields are
start from alkylphosphonic diesters use phosphorous pentachloride
agent. However, phosphorous
mixed. Also, in all cases, one must distill the phosphonic dichloride product. Herein is reported an efficient and
broadly applicable method for generating phosphonic acid dichlorides (1) on large scale without distillation.
Scheme
0
0
oxalyl chloride; DMF
F - O H
-
R
While them are few good methods of monitoring the transformation of carboxylic acids to
acid chlorides apart from derivitization and analysis. one can accurately follow the conversion of phosphonic
acids to phosphonic acid dichlorides by
Table), simplifying analysis.
nmr. Typically, the
signal is shifted 14 to 20 ppm
(see
The phosphonic acid starting materials
either obtained from commercial
or prepared via
Arbuzov chemistry6 followed by acid hydrolysis. The DMF-catalyzed reaction of a phosphonic diacid with
oxalyl chloride is strongly
+ 2
and liberates large quantities of gas, as described by the equation:
+ 2HCl + 2C0 +
Distillation of the crude acid chlorides was not required, but is possible via vacuum distillation. For
acid dichlorides, yields were generally while distilled when performed for comparison to reported
were in the range of 92%. All reagents obtained from commercial sources and used without
7473

7474
further purification, and all
standard in
were recorded at 80.99 MHz on a Varian VXR 200 without internal
nmr
59.6
ppm
40.9
yield,
crude distilled
R
found
178 (21)
94
95
94
92
92
NA
NA
85
127
50.8
52.6
33.1
32.2
32.0
19.2
NA
NA
___
127 (8)
107 (4)
NA
77
93
89
A
105
37.3
47.4
20.9
23.7
(4)
___
N
Typical is the synthesis of phenylphosphonic dichloride. A solution of phenylphosphonic acid
(2.0 G) and anhydrous DMF (10
was gently refluxed in dichloromethane (30
in anhydrous dichloromethane was added, via modified addition
temperature at
C. Upon complete addition of the oxalyl chloride solution, the reaction was held at reflux for
under dry nitrogen. To
this, a solution of oxalyl chloride (2.4
funnel.7 During the addition, copious gas was evolved, and heat was applied to keep the
or above
approximately one hour, then the reflux condenser was replaced
a still head, and the volatiles (distillation
temperature
C at 763 mm) were removed. Analysis of the residual oil (2.29 G; 93%) by nmr
revealed a single peak (see Table), consistent with clean formation of phenylphosphonic dichloride. The product
was distilled only for comparison to the literature value.* and could be used without distillation.
References
la.
lb.
2.
Frank, Arlen W. J. Org. Chem
Helmut; Heuschmann,
1521.
Abdel-Rahman, Mohamed 0. Synthesis, 1974,490.
Maier, Ludwig, Phosphorus,
Silicon,
465.
3a.
3b.
4.
Bhongle. N. N.;
R. H.; Turcotte, J. G. Syn Comm,
H. Chem 1980,435.
1071.
Morita, T.; Okmoto. Y.;
Doak, G. 0.; Freedman, Leon D. J. Am. Chem.
76, 1621.
5.
Freedman, L. D.;
U.S. Patent No.
A
H.; Doak, G. 0.; Magnuson, H. J. J. Am. Chem
1953, 75, 1379.
6.
7.
inventors Karanewsky, D. S., and Petrillo. Jr., E. W.
addition funnel’s
was extended with teflon tuhing such that it
below the surface of the reaction solution.
8.
Fild. M.;
R. and Peake, S. C. in
Phosphorus
G. M.
Kosolapoff
L. Maier, John Wiley Sons, 1972, Vo1.4, page 155.
(Received in USA 22 July 1992; accepted 2 September 1992)