REACTIONS OF TRIALKYL PHOSPHITES WITH MONO- AND DIACYLALS
ture [2]. The unusually easy reaction of I with diacyl- MeCH(OEt)OCOCH2P(O)(OMe)2 + H2O
1739
als of tri- and dichloroacetic acids is apparently due
to additional electron-withdrawing effect of the substi-
tuted acyloxy group in position 1.
(MeO)2P(O)CH2COOH + MeCHO + EtOH,
XIII
IX, Hlg = Br (a), I (b).
Below are the substituents R and X in compounds
VIa and VIb and the NMR data [ , ppm (J, Hz)]: R =
To convert the initial acylal IXa or IXb completely,
we took 1.2 molar equivalents of the phosphite. Di-
methyl methylphosphonate XII and other volatiles
were distilled off in a high vacuum into a trap cooled
1
Me, X = Cl: H: 1.6 d (3H, Me, J 6.3), 3.8 d (6H,
OMe, J 12.0), 6.48 q (1H, CH, J 6.3); 13C: 19.5,
20.0 s (Me), 56.2 s (OMe), 89.0 s (CCl3), 98.5, 99.5 s
3
2
(CH), 136 d (=CCl2, JPC 6.3), 146.1 d (=CO2, JPC
1
with liquid nitrogen. The residue, according to the H
7.6), 161.7 s (C=O); 31P: 6. R = Et, X = Cl: H:
1
and 31P NMR spectra [ , ppm (J, Hz)], was identified
as compound X: 3.7 d (6H, POMe, J 12.0), 2.9 d (2H,
PCH2, J 20.8), 5.85 q (1H, O2CH, J 6.0), 1.25 d (3H,
CHMe, J 6.0), 3.6 q (2H, OCH2Me, J 7.5), 1.1 t (3H,
1.25 t (6H, OCH2Me, J 7.0), 1.58 d (3H, CHMe, J
6.3), 4.12 quintet (4H, OCH2, J 7.0 and 7.0), 6.47 q
1
(1H, CH, J 6.3); 31P: 6. R = Et, X = H: H: 1.26 t
(6H, OCH2Me, J 7.0), 1.6 d (3H, Me, J 6.3), 4.12
quintet (4H, OCH2, J 7.0 and 7.0), 6.48 q (1H, CH,
J 6.3), 6.4 s (1H, CHCl2CO), 6.8 7.3 m (=CHCl);
31P: 6.
OCH2Me, J 7.5);
23 ppm. By distillation of the
condensate from thePtrap, we obtained dimethyl meth-
ylphosphonate; bp 70 71 C (10 12 mm Hg), nD20
1.4105. Published data: bp 67 C (12 mm Hg), nD20
1.4105 [4]. Its NMR spectra had the following charac-
teristics, , ppm (J, Hz): 3.7 d (6H, POMe, J 12.0),
Chloroacetic acid monoacylal shows a weak reac-
tivity toward trialkyl phosphites. Bromoacetic acid
monoacylal IXa reacts with trimethyl phosphite with
a weak exothemic effect: As Ia is added dropwise to
the monoacylal, the temperature of the reaction mix-
ture grows from 18 to 23 C. At the same time, the
reaction of monoiodoacetic acid acylal IXb occurs
with a substantial exothermic effect: As Ia is added
dropwise to IXb, the temperature of the reaction mix-
ture grows from 18 to 33 C. However, in both cases,
the strong odor of the phosphite remains after gradual
spontaneous cooling of the mixture to 20 C. The odor
disappears after heating the reaction mixture at 50
60 C for 2.5 h (Hlg = Br) or at 40 50 C for 2 h
1.3 d (3H, P Me, J 18.0);
34 ppm.
P
Since carboxylic acid monoacylals are readily hy-
drolyzed [5], compound X was subjected to hydrolysis
under similar conditions: A mixture of the monoacylal
of the phosphorylated acetic acid with water was kept
at 50 C for 3 h. The volatiles were removed in a high
vacuum. Crude acid XIII was identified by NMR
spectroscopy, , ppm (J, Hz): 3.6 d (6H, POMe, J
11.5), 2.88 d (2H, PCH2, J 21.0), 9.5 s (1H, COOH);
23 ppm.
P
Previously phosphorylated acetic acids were pre-
pared by oxidation of the corresponding aldehydes
[6]. Our method is a new route to these difficutly
accessible substances.
(Hlg = I). The 31P NMR spectrum of the reaction
mixture after removal of volatiles in a water-jet-pump
vacuum contains a strong singlet with
23 ppm and
a weak signal with
34 ppm. This Pfact suggests
formation of two reactiPon products of the phosphonate
structure. Therefore, we concluded that reaction of I
with IX follows the pattern of the classical Arbuzov
reaction yielding carboxylic acid monoacylal phos-
phorylated in the acid moiety (X) and methyl bromide
or methyl iodide XI. The latter compounds enter into
a competing reaction with the phosphite, yielding a
methylphosphonic acid ester XII. The known P value
for XII is 35 ppm [3].
Since the C Cl is less polarized than the C Br and
C I bonds and the ethoxy group is considerably less
electron-withdrawing than the CCl3COO and CHCl2
COO groups, monoacylals of trichloroacetic (XIVa)
and dichloroacetic (XIVb) acids, compared to com-
pounds IIa, IIb, XIa, and XIb, should be less reactive
in the Perkow and classical Arbuzov reactions. On
the other hand, the trichloro- and dichloroethanoate
groups are sufficiently labile for occurrence of nucleo-
philic substitution at the methine carbon atom of the
monoacylal under the action of trialkyl phosphite
(nonclassical Arbuzov reaction).
MeCH(OEt)OCOCH2Hlg + (MeO)3P
+
NeCH(OEt)OCOCH2P(OMe)3Hlg
Trichloroacetic acid monoacylal XIVa reacted with
trimethyl phosphite with appreciable heat release: As
Ia was added dropwise to the monoacylal, the temper-
ature of the reaction mixture increased from 20 to
30 C. In the subsequent experiments, the temperature
in the course of phosphite addition was kept no higher
MeCH(OEt)OCOCH2P(O)(OMe)2 + MeHlg,
X
XI
MeHlg
(MeO)3P
MeP(O)(OMe)2,
XII
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 73 No. 11 2003