α-Hydroxy- and (α-acyloxyimino)benzylphosphonates

Article abstract of DOI:10.1134/S1070363209020054

N-Hydroxyfluorobenzimidoylphosphonates and their O-acyl derivatives are synthesized. Reaction of phosphorylated oximes with sulfinyl chloride proceeds with rearrangement and leads to synthetically prospective N- sulfonylimidoylphosphonates. By the method

Full text of DOI:10.1134/S1070363209020054

ISSN 1070-3632, Russian Journal of General Chemistry, 2009, Vol. 79, No. 2, pp. 195–199. © Pleiades Publishing, Ltd., 2009.
Original Russian Text © T.I. Chudakova, Yu.V. Rassukanaya, A.A. Sinitsa, P.P. Onys’ko, 2009, published in Zhurnal Obshchei Khimii, 2009, Vol. 79, No. 2,
pp. 207–211.
α-Hydroxy- and (α-Acyloxyimino)benzylphosphonates
T. I. Chudakova, Yu. V. Rassukanaya, A. A. Sinitsa, and P. P. Onys’ko
Institute of Organic Chemistry, National Academy of Sciences of Ukraine,
ul. Murmanskaya 5, Kiev, 02660 Ukraine
e-mail: onysko@rambler.ru
Received August 8, 2008
Abstract―N-Hydroxyfluorobenzimidoylphosphonates and their O-acyl derivatives are synthesized. Reaction
of phosphorylated oximes with sulfinyl chloride proceeds with rearrangement and leads to synthetically
prospective N-sulfonylimidoylphosphonates. By the method of 19F NMR are revealed values of σ-constants of
N-hydroxy- and N-acyloxy substituted imidoylphosphonate groups.
DOI: 10.1134/S1070363209020054
α-Hydroxyiminoalkylphosphonates is a prospective
type of bifunctional organophosphorus compounds.
They are used in the syntheses of amino- [1,2] and
hydroxyaminophosphonic acids [3], have been
proposed as phosphorylating agents via generation of
metaphosphates [4], are potent metal-binding agents
[4]. (α-Acyloxy imino)benzylphosphonates have been
patented as herbicide antagonists [5]. Synthetic
potential of C-phosphorylated oximes has not been
sufficiently studied, the transformations described are
connected mainly with E/Z isomerization, thermal
fragmentation and dealkylation of the phosphorus-
containing fragment [4]. Reaction at azomethine group
are restricted to the reduction of C=N bond, due
probably to insufficient electrophilicity of imine carbon
atom. We suggested that introduction of substituents to
the hydroxy group oxygen atom in N-hydroxyl-
benzimidoylphosphonate could increase electrophilicity
of azomethine bond and might reveal new pathways of
reactions of these compounds.
[4]. In 31Р, 19F NMR spectra of compounds II the
resonance of E isomers occur at weaker field (ΔδP 3.4–
3.5 ppm, ΔδF 0.5–1.4 ppm) as compared with the Z
isomers. The oximes obtained are readily acylating
with acid chlorides or isocyanates. Thus, the reaction
of compounds II with aromatic acid chlorides in the
presence of a base leads to imines III and with 3,4-
dichlorophenylisocyanate are obtained derivatives IV
containing fragments of carbaminic and imidoylphos-
phonic acids (Scheme 1).
Distinctly to the reactions in the scheme 1 leading
to stable О-acylated derivatives, the reaction of
phosphorylated oximes II with 4-tolylsulfinyl chloride
proceeds with rearrangement of the primary products
of О-sulfination (compare [6]) and leads to N-sulfonyl-
imidoylphosphonates (V) (Scheme 2). This reaction is
a new convenient method for the synthesis of С-
phosphorylated N-sulfonylimines that are pros-pective
reactive precursors of aminophosphonic acids [7, 8].
In this work we synthesized N-hydroxyfluorobenz-
imidoylphosphonates and their O-acyl derivatives,
analyzed electronic structure of R-oxyimidoylphos-
phonate groups and studied some properties of the
synthesized С-phosphorylated imines.
Magnetic shielding of fluorine nuclei in substituted
fluorobenzenes depends on the electronic parameters of
substituents at the benzene ring and is widely used for
quantitative revealing the latter [9]. By measuring chem-
ical shifts of fluorine nuclei relatively to internal fluoro-
benzene in imidoylphosphonates II–IV dissolved in
CDCl3 and applying Taft’s equations [10, 11] we for first
time revealed inductive and resonance σ-constants of N-
hydroxy-, N-acyloxyimidoylphosphonate {–C[P(O)·
(OEt)2]=NOX} and phosphorylformyl {–C[P(O)·
(OEt)2]=O} groups.
Reaction of fluorobenzoylphosphonates Ia and Ib
with hydroxylamine hydrochloride in the presence of
pyridine results in formation of С-phosphorylated oximes
IIа and IIb formed as mixtures of E/Z isomers (E/Z
ratio is 2.3 and 2.1, respectively) (Scheme 1). Assign-
ment of the isomers is made on the basis of the data
195

196
CHUDAKOVA et al.
Scheme 1.
(EtO)2P
Ar
O
N
Ar'C(O)Cl
OC(O)Ar'
Et3N
O
(EtO)2P
Ar
O
N
H2NOH
IIIа−IIId
OH
Ar
P(OEt)2
(EtO)2P
Ar
O
O
N
O
Ar''NCO
O
IIа, IIb
Iа, Ib
NHAr''
IVа, IVb
I, II: Ar = 4-FC6H4 (a), 3-FC6H4 (b); III: Ar' = 4-O2NC6H4, Ar = 4-FC6H4 (a), 3-FC6H4 (b); Ar' = 4-ClC6H4, Ar = 4-FC6H4
(c), 3-FC6H4 (d); IV: Ar'' = 3,4-Cl2C6H3, Ar = 4-FC6H4 (a), 3-FC6H4 (b).
Scheme 2.
P(OEt)2
P(OEt)2
N
O
O
MeC6H4SOCl
Et3N
IIа, IIb
Ar
N
OSOC6H4Me-4
Ar
SO2C6H4Me-4
Vа, Vb
As follows from the obtained data (see table), N-
hydroxyimidoylphosphonate group (no. 2) is a weak
electron-acceptor (σp 0.15–0.25) even below N-benzyl
(no. 9) analog by total electron-acceptor effect, that is
reflected by the observed low reactivity of the
phosphorylated oximes. Attaching of acyl (nos. 4–6) or
carbamoyl (nos. 7, 8) group to the oxime О-atom
increases acceptor property substantially: total
electron-acceptor effect of these groups becomes
comparable with that of such strong acceptors as N-
sulfonyl (no. 10) or N-phosphorylimidoyl substituents
(no. 11). Interesting to note that electronic effect
NMR chemical shifts of fluorosubstituted benzenes XC6H4F and σ-constants of N-substituted imidoylphosphonate groups
δF(XC6H4F)
Run
X
σI
σR
σp
no.
3-F
2.23
0.69
0.21
1.92
1.17
2.18
2.18
1.41
1.80
2.09
1.90
2.05
4-F
11.72
2.74
1.35
4.88
4.34
5.45
5.38
4.33
2.38
7.42
7.10
7.42
1
2
3
4
5
6
7
8
9
O=C[P(O)(OEt)2]–
0.40
0.18
0.11
0.35
0.25
0.39
0.39
0.28
0.34
0.38
0.35
0.37
0.32
0.07
0.04
0.10
0.11
0.11
0.11
0.10
0.02
0.18
0.18
0.18
0.72
(E)-HON=C[P(O)(OEt)2]–
0.25
(Z)-HON=C[P(O)(OEt)2]–
0.15
(E)-4-ClC6H4COON=C[P(O)(OEt)2]–
(Z)-4-ClC6H4COON=C[P(O)(OEt)2]–
(E)-4-O2NC6H4COON=C[P(O)(OEt)2]–
(E)-3,4-Cl2C6H3NHCOON=C[P(O)(OEt)2]–
(Z)-3,4-Cl2C6H3NHCOON=C[P(O)(OEt)2]–
PhCH2N=C[P(O)(OEt)2]–
0.45
0.36
0.50
0.50
0.38
0.36 [12]
0.56 [13]
0.53
10 PhSO2N=C[P(O)(OEt)2]–
11 TsN=C[P(O)(OEt)2]–
12 (EtO)2P(O)N=C[P(O)(OPh)2]–
0.55 [8]
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α-HYDROXY- AND (α-ACYLOXYIMINO)BENZYLPHOSPHONATES
depends on the geometry of imidoylphosphoryl group:
in all cases the electron–acceptor ability is higher at Е
configuration of substituents at the azomethine bond.
From the analysis of the data in the table follows that
electron–acceptor property of oxo- or iminomethyl-
phosphoryl group (EtO)2P(O)C(=X)– raises in the follow-
ing series, depending on the unsaturated substituent Х:
references, TMS (1Н), CFCl3 or PhF (19F), and external
85% Н3РО4 (31Р). All reactions were carried out under
anhydrous conditions, under argon atmosphere.
N-Hydroxyimidoylphosphonates (II). A mixture
of 4 mmol of ketophosphonate I, 5.2 mmol of hydroxyl-
amine hydrochloride and 5.6 mmol of pyridine in 2 ml
of anhydrous ethanol was stirred at room temperature
for 36 h. The solvent was evaporated and residue was
washed with water, extracted with ether, and dried
over MgSO4. After evaporation of solvent was isolated
compound II.
NOH < NCH2Ph < NOC(O)R < NP(O)OEt)2
NSO2Ph < O.
<
The obtained values of σ-constants (see table) show
that О-acylated imidoylphosphonates III are enough
electrophilic systems. Actually, in distinct to the phos-
phorylated oximes II they react with O- and N-
centered nucleophiles under mild conditions. Reactions
with methanol or benzylamine proceed at the most
electrophilic center, carbonyl group, and leads to
formation of oxime IIа and methyl ester VI or benz-
ylanide VII, respectively (Scheme 3). Thus, com-
pounds III are soft acylating agents.
Diethyl N-hydroxy-4-fluorobenzimidoylphospho-
1
nate (IIа). Yield 72%, oil. The H NMR spectrum
(CDCl3), δ, ppm: 1.21 (E) and 1.22 (Z), overlapping
3
triplets (6Н, СН3, JHH 7 Hz), 4.0–4.2 m (4H, СН2),
7.0 m (2Н, Ar), 7.6 m (2Н, Ar), 10.56 br (E), 11.81 br
(Z). The 19F NMR spectrum (CDCl3), δF, ppm: –112.89
31
(E), –113.37 (Z). The P NMR spectrum (CDCl3), δP,
ppm: 9.4 (E), 6.0 (Z), E/Z ~ 2.1. Found, %: N 4.86; P
10.94. C11H15FNO4P. Calculated, %: N 5.09; P 11.25.
Scheme 3.
IIIа
Diethyl N-hydroxy-3-fluorobenzimidoylphospho-
1
nate (IIb). Yield 68%, oil. The H NMR spectrum
PhCH2NH2
−IIа MeOH
−IIа
(CDCl3), δ, ppm: 1.21 (E) and 1.22 (Z), overlapping
triplets (6Н, СН3, 3JHH 7 Hz), 4.0–4.2 m (4H, СН2), 7.0
m (1Н, Ar), 7.2 m (3Н, Ar), 10.9 br (E), 12.1 br (Z).
The 19F NMR spectrum (CDCl3), δF, ppm: –112.89
(E), –113.37 (Z). The P NMR spectrum (CDCl3), δP,
ppm: 8.5 (E), 5.0 (Z). E/Z ~ 2.2. Found, %: N 4.78; P
O2N
CONHCH2Ph
COOMe
O2N
31
VI
VII
10.80. C11H15FNO4P. Calculated, %: N 5.09; P 11.25.
The N-sulfonylimidoylphosphonates (V) prepared
from the oximes (Scheme 2) are even stronger electro-
philes (see table, no. 11). Unlike the О-acylated com-
pounds III, they react with О-, S- and Р-centered
nucleophiles at the C=N bond forming functional
aminophosphonic acid derivatives [8, 13].
N-Acyloxy imidoylphosphonates (III). To a solu-
tion of 1 mmol of oxime II and 1.2 mmol of triethyl-
amine in 3 ml of benzene was added at stirring 1 mmol
of respective acid chloride. The mixture was stirred at
60°С for 3 h. Residue was filtered off and filtrate was
washed with water and dried (MgSO4). After
evaporation of the solvent the residue was wear out
with petroleum ether.
Thus, modification of the substituent at the oxygen
atom of hydroxyimidoylphosphonate allows to increase
substantially its electrophilicity and to change re-
activity of the corresponding С-phosphorylated imines.
Diethyl N-(4-nitrobenzoyloxy)-4-fluorobenzimid-
oylphosphonate (IIIa). Yield 59%, mp 73–75°С. The
1H NMR spectrum (CDCl3), δ, ppm: 1.31 t (Z) and
EXPERIMENTAL
3
1.41 t (E) (6Н, СН3, JHH 7 Hz), 4.2 m (Z), 4.3 m (E),
(4H, СН2), 7.1–7.3 m (2Н, FAr), 7.69 d.d (J 8.4 and
5.9 Hz) (E), 7.79 d.d (J 8.4 and 5.4 Hz) (Z) (2Н, FAr),
8.00 d (J 9.3 Hz) (E) and 8.38 d (J 9 Hz) (Z) (2Н,
O2NAr), 8.28 d (J 9.3 Hz) (E) and 8.49 d (J 9 Hz) (Z)
(2Н, O2NAr). The 19F NMR spectrum (CDCl3), δF, ppm:
–108.21 (E), –108.74 (Z). The 31P NMR spectrum
(CDCl3), δP, ppm: 5.9 (E), 1.5 (Z), E/Z ~ 5.9. Found,
The IR spectra were registered on an UR–20
spectrophotometer. The 1Н NMR spectra were
recorded on a NMR spectrometer Varian VXR-300,
operating frequency 299.95 MHz, the 19F and 31Р
NMR spectra on a Varian Gemini–200 instrument,
operating frequencies 188.28 and 81.03 MHz, respect-
ively. Chemical shifts are given relatively to internal
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198
CHUDAKOVA et al.
%: C 51.36; H 4.42; N 6.51; P 7.45. C18H18FN2O7P.
Calculated, %: C 50.95; H 4.28; N 6.60; P 7.30.
(Z), E/Z ~ 3.2. Found, %: Cl 15.59; P 6.72. C18H18·
Cl2FN2O5P. Calculated, %: Cl 15.31; P 6.69.
Diethyl N-(3,4-dichlorophenylcarbamoyloxy)-3-
fluorobenzimidoylphosphonate (IVb). Yield 48%,
mp 87–89°С. The 1H NMR spectrum (CDCl3), δ, ppm:
1.26 (Z) and 1.28 (E), overlapping triplets (6Н, СН3,
3JHH 7 Hz), 4.0–4.2 m (4H, СН2), 7.0–7.4 m (6Н, Ar),
7.45 d (Z) and 7.61 d (E) (1Н, Cl2C6H3), 8.1 br (Z) and
8.2 br (E) (1Н, NH). The 19F NMR spectrum (CDCl3),
δF, ppm: –111.44 (E), –112.21 (Z). The 31P NMR spec-
trum (CDCl3), δP, ppm: 5.3 (E), 0.1 (Z), E/Z ~ 5.9.
Found, %: N 5.94; P 6.63. C18H18Cl2FN2O5P. Cal-
culated, %: N 6.05; P 6.69.
Diethyl N-(4-nitrobenzoyloxy)-3-fluorobenzimid-
oylphosphonate (IIIb). Yield 64%, mp 89–90°С. The
1H NMR spectrum (CDCl3), δ, ppm: 1.31 t (Z) and
3
1.40 t (E) (6Н, СН3, JHH 7 Hz), 4.2 m (Z), 4.3 m (E),
(4H, СН2), 7.2–7.6 m (4Н, FAr), 7.99 d (J 9 Hz) (E)
and 8.38 d (J 9 Hz) (Z) (2Н, O2NAr), 8.27 d (J 9 Hz)
(E) and 8.50 d (J 9 Hz) (Z) (2Н, O2NAr). The 19F
NMR spectrum (CDCl3), δF, ppm: –111.41 (E), –112.23
(Z). The 31P NMR spectrum (CDCl3), δP, ppm: 4.7 (E),
1.4 (Z), E/Z ~ 10. Found, %: N 6.43; P 7.52.
C18H18FN2O7P. Calculated, %: N 6.60; P 7.30.
Reaction of p-nitrobenzoyloxyimidoylphosphonate
(IIIа) with methanol (Scheme 3). A solution of com-
pound IIIа (1 mmol) in 1 ml of methanol was refluxed
Diethyl
N-(4-chlorobenzoyloxy)-4-fluorobenz-
1
imidoylphosphonate (IIIc). Yield 73%, oil. The H
NMR spectrum (CDCl3), δ, ppm: 1.27 (Z) and 1.35 (E)
(6Н, СН3, JHH 7 Hz), 4.1 m (Z), 4.29 quintet, J 7 Hz
1
for 6 h. Methanol was evaporated. Н and 31Р NMR
3
analysis showed quantitative formation of oxime IIа
and methyl p-nitrobenzoate identified by comparison
with authentic samples.
(E), (4H, СН2), 7.1–7.2 m (2Н, FAr), 7.37 d (J 8.3 Hz)
(E) and 7.48 d (J 8.3 Hz) (Z) (2Н, ClAr), 7.6–7.7 m
(2Н, FAr), 7.73 d (J 8.3 Hz) (E) and 8.16 d (J 8.3 Hz)
(Z) (2Н, ClAr). The 19F NMR spectrum (CDCl3), δF,
ppm: –108.74 (E), –109.30 (Z). The 31P NMR spec-
trum (CDCl3), δP, ppm: 5.2 (E), 0.7 (Z), E/Z ~ 10.
Found, %: Cl 8.43; N 3.24; P 7.67. C18H18ClFNO5P.
Calculated, %: Cl 8.57; N 3.39; P 7.49.
Reaction of p-nitrobenzoyloxyimidoylphosphonate
(IIIа) with benzylamine (Scheme 3). To a solution of
0.07 g (0.16 mmol) of imidoylphosphonate IIIа in 0.5 ml
of benzene was added at 5°С 0.017 g (0.16 mmol) of
benzylamine. After 2-h reflux the solvent was eva-
porated and residue was washed with petroleum ether.
Diethyl N-(4-chlorobenzoyloxy)-3-fluorobenzimid-
oylphosphonate (IIId). Yield 76%, oil. The 1H NMR
spectrum (CDCl3), δ, ppm: 1.22 (Z) and 1.31 (E) (6Н,
1
The residue by the data of Н and 31Р NMR spec-
troscopy contained p-nitrobenzylamide and oxime IIа
that were identified by comparison with authentic
samples.
3
СН3, JHH 7 Hz), 4.1 m (Z), 4.25 quintet, J 7 Hz (E),
(4H, СН2), 7.0–7.5 m (4Н, FAr), 7.33 d (J 8.5 Hz) (E)
and 7.95 d (J 8.1 Hz) (Z) (2Н, ClAr), 7.68 d (J 8.1 Hz)
(E) and 8.16 d (J 8.5 Hz) (Z) (2Н, ClAr). The 19F NMR
spectrum (CDCl3), δF, ppm: –111.75 (E), –112.50 (Z).
Imidoylphosphonates (V). To a solution of 1 mmol
of oxime II and 1.1 mmol of triethylamine in 3 ml of
ether was added at stirring and cooling with ice 1 mmol
of 4-tolylsulfinyl chloride. The temperature was allowed
to reach room one and the mixture was left overnight.
The precipitate was filtered off, the filtrate was
evaporated and the residue was washed with petroleum
ether.
31
The P NMR spectrum (CDCl3), δP, ppm: 5.4 (E), 0.8
(Z), E/Z ~ 2. Found, %: Cl 8.72; N 3.47; P 7.27. C18H18·
ClFNO5P. Calculated, %: Cl 8.57; N 3.39; P 7.49.
N-Carbamoyloxyimidoylphosphonates (IV). Equi-
molar mixture of oxime II and 3,4-dichlorophenyl-
isocyanate was stirred at 60°С for 6 h. Solvent was
then evaporated and residue ws wear with hexane.
Diethyl N-(4-tolylsulfonyl)-4-fluorobenzimidoyl-
1
phosphonate (Vа). Yield 68%, oil. The H NMR
spectrum (CDCl3), δ, ppm: 1.21 m (6Н, СН3), 2.44 s
(3Н, СН3С6Н4), 4.02–4.18 m (4Н, СН2), 7.15 d.d (2Н,
Ar, JHH 8 Hz, JHF 8 Hz), 7.31 d (2Н, Ar, JHH 8 Hz),
7.80 d (2Н, Ar, 3JHH 8 Hz), 7.83–7.87 m (2Н, Ar). The
19F NMR spectrum (CDCl3), δF, ppm: –106.5. The 31P
NMR spectrum (CDCl3), δP, ppm: 2.5.
Diethyl N-(3,4-dichlorophenylcarbamoyloxy)-4-
fluorobenzimidoylphosphonate (IVа). Yield 84%,
mp 74–76°С. The 1H NMR spectrum (CDCl3), δ, ppm:
1.26 (Z) and 1.29 (E), overlapping triplets (6Н, СН3,
3JHH 7 Hz), 4.0–4.2 m (4H, СН2), 7.0–7.6 m (7Н, Ar),
8.0 br (E) and 8.3 br (Z) (1Н, NH). The 19F NMR
spectrum (CDCl3), δF, ppm: –108.23 (E), –109.27 (Z).
The 31P NMR spectrum (CDCl3), δP, ppm: 5.7 (E), 0.6
3
3
3
Diethyl N-(4-tolylsulfonyl)-3-fluorobenzimidoyl-
1
phosphonate (Vb). Yield 60%, oil. The H NMR
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 79 No. 2 2009

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α-HYDROXY- AND (α-ACYLOXYIMINO)BENZYLPHOSPHONATES
6. Boger, D., Corbett, W. L., Curran, T.T., and Kasper, A.M.,
spectrum (CDCl3), δ, ppm: 1.21 m (6Н, СН3), 2.43 s
(3Н, СН3С6Н4), 4.03–4.19 m (4Н, СН2), 7.21 m (1Н,
Ar), 7.30 d (2Н, Ar, 3JHH 8 Hz), 7.41–7.57 m (3Н, Ar),
J. Am. Chem. Soc., 1991, vol. 113, no. 5, p. 1713.
7. Rassukana, Yu.V., Onys’ko, P.P., Grechukha, A.G., and
3
7.77 d (2Н, Ar, JHH 8 Hz). The 19F NMR spectrum
Sinitsa, A.D., Eur. J. Org. Chem., 2003, no. 21, p. 418.
(CDCl3), δF, ppm: –111.7. The 31P NMR spectrum
(CDCl3), δP, ppm: 2.6.
8. Kolotilo, N.V., Sinitsa, A.A., Rassukanaya, Yu.V., and
Onys’ko, P.P., Zh. Obshch. Khim., 2006, vol. 76, no. 8,
p. 1260.
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