Reactions of phosphorodiamidous acid esters with α-halocarbonyl compounds

Article abstract of DOI:10.1023/A:1023397330794

Reactions of ethyl and tert-butyl phosphorodiamidites with chloroacetone, bromoacetone, and α-chloroethyl acetate were studied. The reaction pathway is determined by the structure of the intermediate quasiphosphonium compound responsible for the formation

Full text of DOI:10.1023/A:1023397330794

Russian Journal of General Chemistry, Vol. 72, No. 11, 2002, pp. 1760 1763. Translated from Zhurnal Obshchei Khimii, Vol. 72, No. 11, 2002,
pp. 1864 1867.
Original Russian Text Copyright
2002 by Sal’keeva, Nurmaganbetova, Kurmanaliev, Gazizov.
Reactions of Phosphorodiamidous Acid Esters
with -Halocarbonyl Compounds
L. K. Sal’keeva, M. T. Nurmaganbetova, O. Sh. Kurmanaliev, and T. Kh. Gazizov
Buketov Karaganda State University, Karaganda, Kazakhstan
Received February 14, 2001
Abstract Reactions of ethyl and tert-butyl phosphorodiamidites with chloroacetone, bromoacetone, and
-chloroethyl acetate were studied. The reaction pathway is determined by the structure of the intermediate
quasiphosphonium compound responsible for the formation of the Arbuzov product as well as for the
occurrence of the amonalous reaction yielding vinyl phosphate.
It is known that the reactions of trialkyl phosphites
with alkyl and acyl halides [1, 2] and of phosphor-
amidous [3] and phosphorothious [4] acid esters with
alkyl halides yield phosphonates. Phosphoramidous
acid esters react with acyl halides by two pathways:
with the formation of the Arbuzov products and with
substitution of the amide group of phosphite with the
halogen atom of acyl halide [5]. Reactions of phos-
phorothious acid esters with acyl halides yield ex-
clusively the products of substitution of alkylthio
group by the halogen atom [6]. Formation of phos-
phonates agrees with the scheme of the Arbuzov re-
action and is beyond doubt. At the same time, the
majority of researchers consider that, in the mech-
anism of substitution with the preservation of phos-
phorus coordination, the role of the nucleophilic
center of the P(III) derivative is played by the hetero-
atom bound to phosphorus and having an unshared
electron pair. On the whole, the reaction follows the
scheme of four-centered electron transfer (pathway 1,
Scheme 1) [5] or occurs via the formation of an onium
intermediate followed by substitution of the onium
action and the substitution proceed through the same
P-acylated derivative, then the yields of the products
of these reactions should be determined by the
properties of the intermediate. The shift of the equilib-
rium in the quasiphosphonium intermediate toward
the ionic form should favor the formation of the
Arbuzov products (the species responsible for the
occurrence of the second stage of the Arbuzov reac-
tion is the ionic form of the quasiphosphonium com-
pound [9]), and, vice versa, shift of the equilibrium
toward the pentacovalent form of the intermediate
should favor the formation of P(III) compounds.
Artificial alteration of the dealkylation rate (stage 3b)
should also considerably affect the process direction.
With the aim to elucidate the mechanism of the reac-
tion of phosphorothious and phosphoramidous acid
esters with acyl halides, we have previously studied
these reactions under different conditions influencing
the state of the quasiphosphonium compound. These
studies were based on the fact that polar solvents [9]
and also passing from acyl chlorides to acyl iodides
(low-basic anions in quasiphosphonium compounds
group by the counterion of the system (pathway 2) [7]. are ionized more readily [10]) favor the formation of
Studies of the reactions of phosphorus amides and
phosphoramidous acid esters with anhydrides and acyl
halides [8] showed that the products of substitution
can be formed also through the P-acylated inter-
mediate (pathway 3a2). If the species responsible for
formation of substitution products with the preserva-
tion of the phosphorus coordination were the product
of acylation by the heteroatom, the yield of the sub-
stitution products would, apparently, increase in going
from phosphorothious to phosphorous and then to
phosphoramidous acid esters, simultaneously with an
increase in the basicity of the heteroatom. However,
as shown in [3-6], in the transformations under con-
sideration this rule is not obeyed. If the Arbuzov re-
the ionic form of the intermediate. Also, it is known
that the tert-butyl group is very rapidly eliminated in
the second stage of the Arbuzov reaction [11, 12]. The
results of our previous studies show [13, 14] that the
direction of the reactions of phosphorous, phosphoro-
thious, and phosphoramidous acid esters is determined
by the properties of quasiphosphonium compounds.
These reactions can be described by a common
scheme (Scheme 1, pathway 3) including the forma-
tion of a P-acylated intermediate (Scheme 1).
Proceeding with studies in this direction, we
examined the reactions of phosphoramidous acid
esters with -halocarbonyl compounds. Published data
1070-3632/02/7211-1760$27.00 2002 MAIK Nauka/Interperiodica

REACTIONS OF PHOSPHORODIAMIDOUS ACID ESTERS
1761
Scheme 1.
Y = NR2, OR, SR.
[15] show that phosphoramidites react with chloro-
acetone to give the products of the phosphonate
(Abramov product) and phosphate (Perkow product)
structure. We have thoroughly studied the reactions
of tert-butyl and ethyl phosphorodiamidites with
chloro- and bromoacetone. We found that the reaction
of tert-butyl phosphorodiamidite with chloroacetone
under various conditions (heating for 2 3 h at 85
90 C) yields phosphorodiamidic chloride III and
vinyl phosphorodiamidate IV in a 2:1 ratio, accord-
ing to the 31P NMR data. The reaction with bromo-
acetone proceeds on cooling (from 20 to 10 C);
it is accompanied by considerable heat evolution and
yields phosphorodiamidic bromide as a virtually
single product. Its structure was proved by indepen-
dent synthesis. Ethyl phosphorodiamidite reacts
with chloroacetone to give a mixture of products III
and IV in a 1:3 ratio. The reaction with bromo-
acetone gives similar products in a 1:2 ratio
(Scheme 2).
Scheme 2.
OR
O
(Et2N)2POR + XCH2 C CH3
I, II
1
(Et2N)2P+
O
C
H3C
CH2X
2
OR
(Et2N)2P+
O
C
OR
(Et2N)2P+X
2b
1b
CH3
CH2
X
O C=CH2
CH3
2a, 1b
O
O
O
(Et2N)2P O C=CH2 + R X
IV
(Et2N)2P X + CH3 C CH2R
III
CH3
R = t-Bu
R = t-Bu
(CH3)2C=CH2 + X
(CH3)2C=O + (CH3)2C=CH2
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 72 No. 11 2002

1762
SAL’KEEVA et al.
We believe that vinyl phosphate IV is formed in
action with -halocarboxylates, in particular, with
ethyl -chloroacetate. According to published data
[16], alkyl phosphorodiamidites react with alkyl
chloroacetates to give exclusively the Perkow prod-
ucts, namely, the corresponding vinyl phosphates.
We have studied the reactions of tert-butyl and ethyl
phosphorodiamidites with ethyl chloroacetate. We
found that these reactions occur at 80 85 C within
these reactions by the scheme of the Perkow reaction
(pathway 1a). Formation of phosphorodiamidic halide
III presumably involves the attack of the electron-
deficient halogen atom of -halocarbonyl compound
by the phosphorus atom of phosphite (pathway 2a).
Anion exchange (pathways 1b, 2b), apparently, can
occur also.
1 2 h and yield phosphorodiamidic chloride (
26 ppm) as the only phosphorus-containing product.
The reaction pathway is described by Scheme 3.
To confirm the presumed mechanism of the reac-
tions of phosphoramidous acid esters with -halo-
carbonyl compounds, it is interesting to study the re-
P
Scheme 3.
OR
(Et2N)2P+ Cl EtO C CH2
O
O
I, II + ClCH2 C OEt
O
O
(Et2N)2P Cl + RCH2 C OEt
III
R = t-Bu
O
CH3C OEt + (CH3)2C=CH2
R = t-Bu (I), Et (II).
Our experimental data also show that the direction
of reactions of phosphoramidous acid esters with
-halocarbonyl compounds is determined by the
properties of the quasiphosphonium intermediates. In
detail, with bromoacetone used instead of chloro-
acetone, the yield of the Arbuzov product increases,
because the anions of low basicity (in our case, Br )
are more readily ionized, which facilitates the forma-
tion of the ionic form of the intermediate. Also, tert-
butyl phosphorodiamidite forms the Arbuzov product
as the major or the only product, because the second
stage of the SN1 reaction is accelerated.
ultaneous distillation of acetone (2.7 g, 61%). Elim-
ination of isobutylene was observed. Distillation of
the reaction mixture gave 9.4 g (55.2%) of tetraethyl-
phosphorodiamidic chloride, bp 71 72 C (0.07 mm),
d240 1.0682, n2D0 1.4680,
26 ppm [published data
P
[17]: bp 68 70 C (0.05 mm), n2D0 1.4648, d420 1.0680],
and 3.7 g (24.8%) of 1-methylvinyl tetraethylphos-
phorodiamidate, bp 58 59 C (0.05 mm), n2D0 1.4580,
d240 1.0120,
12 ppm [published data [18]: bp
P
124 128 C (8 mm), nD20 1.4520, d240 0.9920]. IR spec-
1
trum, , cm : 1640 (C=C), 1260 (P=O).
Reaction of ethyl tetraethylphosphorodiamidite
with chloroacetone was performed similarly. Phos-
phite II, 11.0 g, and chloroacetone, 4.6 g, gave tetra-
ethylphosphorodiamidic chloride III and 1-methyl-
vinyl tetraethylphosphorodiamidate IV in a 1:3 ratio.
EXPERIMENTAL
The 31P NMR spectra were taken on a custom-
made KGU-4 spectrometer (10.2 MHz) against ex-
1
ternal 85% phosphoric acid. The H NMR spectra
Reaction of phosphite I with bromoacetone.
Bromoacetone, 3.4 g, was added at a temperature
from 20 to 10 C to 6.2 g of phosphite I. Con-
siderable heat evolution was observed, and 450 ml
(80.4%) of isobutylene was released. Distillation of
the reaction mixture gave 5.0 g of tetraethylphosphoro-
diamidic bromide, P 19 ppm. Its structure was proved
by independent syntheses. The reaction of tetraethyl-
were recorded on a Varian T-60 spectrometer
(60 MHz) against external TMS. The IR spectra were
measured on a UR-20 spectrometer in liquid films.
Reaction of tert-butyl tetraethylphosphorodi-
amidite with chloroacetone. Chloroacetone, 6.9 g,
was added to 18.6 g of phosphite I, and the resulting
mixture was heated at 85 90 C for 2 3 h with sim-
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 72 No. 11 2002

REACTIONS OF PHOSPHORODIAMIDOUS ACID ESTERS
1763
phosphorodiamidic bromide with 2 equivalents of di-
5. Antokhina, L.A. and Alimov, P.I., Izv. Akad. Nauk
SSSR, Ser. Khim., 1971, no. 4, p. 806.
ethylamine gave hexaethylphosphorotriamide with
P
23 ppm (published data [19]: P 23.5 ppm). Oxidation
of ethyl phosphorodiamidite with molecular bromine
6. Al’fonsov, V.A., Zamaletdinova, G.U., Batyeva, E.S.,
and Pudovik, A.N., Izv. Akad. Nauk SSSR, Ser. Khim.,
1982, no. 6, p. 1386.
yields phosphorodiamidic bromide with
19 ppm.
P
7. Hudson, R.F. and Searle, R.J.G., Chimia, 1966,
vol. 20, p. 117.
8. Hargis, J.H. and Mattison, G.A., J. Org. Chem., 1981,
vol. 46, no. 8, p. 1597.
9. Gazizov, T.Kh., Cand. Sci. (Chem.) Dissertation,
1969.
10. Nesterov, L.V. and Aleksandrova, I.A., Zh. Obshch.
Khim., 1980, vol. 50, no. 1, p. 36.
11. Gusev, Yu.K., Chistokletov, V.N., and Petrov, A.A.,
Zh. Obshch. Khim., 1977, vol. 47, no. 1, p. 45.
12. Gazizov, T.Kh., Chugunov, Yu.V., and Pudovik, A.N.,
Dokl. Akad. Nauk SSSR, 1987, vol. 294, no. 6,
p. 1382.
of tetraethylphosphorodiamidic chloride III, bp 68
13. Gazizov, T.Kh., Sal’keeva, L.K., Gafurov, E.K., and
Kazantsev, A.V., Zh. Obshch. Khim., 1988, vol. 58,
no. 5, p. 1155.
70 C (0.05 mm), n2D0 1.4648, d420 1.0680,
26 ppm.
P
Reaction of ethyl tetraethylphosphorodiamidite
with ethyl chloroacetate was performed similarly.
Phosphite II, 5.5 g, and 3.05 g of ethyl chloroacetate
gave 5.7 g (82%) of tetraethylphosphorodiamidic
14. Gazizov, T.Kh., Sal’keeva, L.K., Gafurov, E.K., and
Kazantsev, A.V., Zh. Obshch. Khim., 1988, vol. 58,
no. 4, p. 944.
chloride ( 26 ppm) and 4.8 g (84.2%) of ethyl
P
15. Abramov, V.S. and Il’ina, I.A., Dokl. Akad. Nauk
SSSR, 1960, vol. 132, no. 4, p. 823.
butyrate.
16. Abramov, V.S. and Il’ina, I.A., Dokl. Akad. Nauk
SSSR, 1964, vol. 155, no. 1, p. 112.
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