Electrophilic Catalysis in the Synthesis of Aryl Methyl- and Phenylphosphonochloridates

Article abstract of DOI:10.1134/S1070363218090025

The reaction of methyl- and phenylphosphonic dichlorides with phenols in the presence of anhydrous magnesium chloride as catalyst or magnesium metal as precatalyst provides a simple, efficient, and practical method of synthesis of the corresponding aryl m

Full text of DOI:10.1134/S1070363218090025

ISSN 1070-3632, Russian Journal of General Chemistry, 2018, Vol. 88, No. 9, pp. 1776–1779. © Pleiades Publishing, Ltd., 2018.
Original Russian Text © E.I. Goryunov, I.B. Goryunova, G.N. Molchanova, I.Yu. Kudryavtsev, T.V. Baulina, A.A. Khodak, T.V. Strelkova, V.K. Brel, 2018,
published in Zhurnal Obshchei Khimii, 2018, Vol. 88, No. 9, pp. 1426–1430.
Dedicated to the 110th anniversary of M.I. Kabachnik’s birth
Electrophilic Catalysis in the Synthesis
of Aryl Methyl- and Phenylphosphonochloridates
E. I. Goryunova*, I. B. Goryunovaa, G. N. Molchanovaa, I. Yu. Kudryavtseva, T. V. Baulinaa,
A. A. Khodaka, T. V. Strelkovaa, and V. K. Brela
a Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences,
ul. Vavilova 28, Moscow, 119991 Russia
*e-mail: gor.evg@rambler.ru
Received June 29, 2018
Abstract—The reaction of methyl- and phenylphosphonic dichlorides with phenols in the presence of
anhydrous magnesium chloride as catalyst or magnesium metal as precatalyst provides a simple, efficient, and
practical method of synthesis of the corresponding aryl methyl- and phenylphosphonochloridates.
Keywords: methylphosphonic dichloride, phenylphosphonic dichloride, phosphorylating agent, phenols, phos-
phorylation, aryl methyl(phenyl)phosphonochloridates
DOI: 10.1134/S1070363218090025
Aryl phenyl- and methylphosphonochloridates are
widely used as starting compounds in the synthesis of
various practically important organophosphorus
compounds, in particular extractants for f-elements
[1, 2], fire-retardant additives for polymeric materials
[3, 4], and especially biologically active substances
[5–11]. However, none of the currently known methods
for the preparation of aryl phenyl- and methyl-
phosphonochloridates is free from some disadvantages.
For instance, the most frequently used synthesis based
on the reaction of the corresponding organylphos-
phonic dichlorides RP(O)Cl2 [1, R = Ph (a), Me (b)]
with phenols in the presence of a tertiary amine as
hydrogen chloride acceptor requires large amounts of
organic solvents, and the isolated products are not
always as pure as necessary [5, 10, 12]. Although aryl
methylphosphonochloridates free from tertiary amine
hydrochloride impurity can be obtained by analogous
reaction in the absence of tertiary amine, the process
requires prolonged heating at elevated temperature,
which reduces the yield of the target products [13].
Institute of Organoelement Compounds, Russian Academy
of Sciences) under the guidance of Academician
M.I. Kabachnik [14]. In fact, it was found that phos-
phorylation of phenol with the simplest alkyl(or aryl)-
phosphonic dichlorides (1a, 1b) can be catalyzed by a
number of metal salts possessing Lewis acid properties
(e.g., anhydrous lithium, magnesium, and calcium
chlorides; magnesium dichloride turned out to be the
most effective), as well as by magnesium metal1 acting
as precatalyst. In this case, neither hydrogen chloride
acceptor nor organic solvent is required. Catalytic
reactions are characterized by a high rate even at
moderate temperature provided that the phosphorylat-
ing agent is taken in excess (the optimal amounts are
2 mol of 1a and 3 mol of 1b), and the target phos-
phonochloridates RP(O)(Cl)OPh (2a, 2b) are obtained in
fairly high yields (66–91%; Scheme 1) with high purity.
The catalytic reactions are easily scalable, and
excess phosphorylating agent can be recovered from
the reaction mixture with high yield and purity, so that
it can be recycled without additional purification.
Thus, the catalytic processes are very attractive from
the practical viewpoint.
A way to improve the efficiency of the above
reaction could be electrophilic catalysis which was
successfully used previously in the synthesis of various
polyfluoroalkyl phosphonochloridates at the Organo-
phosphorus Compounds Laboratory (Nesmeyanov
1
Magnesium metal dissolves during the reaction to form
magnesium chloride.
1776

ELECTROPHILIC CATALYSIS IN THE SYNTHESIS OF ARYL METHYL-
1777
Scheme 1.
Scheme 2.
120°C, [Mg]
ArOH + MeP(O)Cl2
MeP(O)(OAr)Cl,
4a−4i
120°C, [MgCl2/Mg]
PhOH + RP(O)Cl2
RP(O)(OPh)Cl,
1
:
3
1
:
2−3
3a−3i
1b
1a, 1b
2a, 2b
Ar = 4-FC6H4 (a), 4-ClC6H4 (b), 4-EtC6H4 (c), 4-iso-PrC6H4
(d), 4-tert-BuC6H4 (e), 2-MeOC6H4 (f), 4-MeOC6H4 (g),
2,6-Me2C6H3 (h), 2-Cl-5-MeC6H3 (i).
R = Ph (a), Me (b).
The next stage of our study was aimed at estimating
the scope of application of electrophilic catalysis in the
synthesis of aryl organylphosphonochloridates.
31P–{1H} NMR spectra, which is consistent with the
presumed structure. As expected, the phosphorus
signal of 4b–4i was a singlet, whereas fluorine-contain-
ing compound 4a displayed a doublet signal of the
phosphorus atom due to long-range coupling with
fluorine.
It should be noted that the use of phenyl
phenylphosphonochloridate (2a) for the preparation of
physiologically active compounds (the major field of
application of organylphosphonochloridates) has been
reported [11]; however, phenyl methylphosphono-
chloridate (2b) turned out to be the most appropriate
for this purpose [5–10]. Therefore, we examined
phosphorylation of a series of commercially available
mono- and disubstituted phenols 3a–3i with 3 mol of
of methylphosphonic dichloride (1b) on heating in the
presence of magnesium metal2 as precatalyst (Scheme 2).
Fractional distillation of the reaction mixtures under
reduced pressure afforded analytically and spectrally
pure aryl methylphosphonochloridates 4a–4i3 in fairly
high yields (61–89%). As in the catalytic synthesis of
methylphosphonochloridate 2b, excess phosphorylat-
ing agent can readily be regenerated, and it is
sufficiently pure to be recycled.
Thus, our results demonstrated that electrophilic
catalysis provides a general, simple, efficient, and practical
synthetic approach to various aryl methylphosphono-
chloridates, which makes these practically important
organophosphorus reagents readily accessible. Further-
more, the proposed method can be successfully applied
to the synthesis of both other representatives of the
same series and structurally related aryl alkyl(aryl)
phosphonochloridates.
EXPERIMENTAL
1
1
31
The H, H–{31P}, 13C, 19F, and P NMR spectra
were recorded on a Bruker AV-400 spectrometer at
[400.13 (1H), 100.61 (13C), 376.49 (19F), and
161.98 MHz (31P)] either without a solvent (compounds
The structure of phosphoryl chlorides 4a–4i was
1
13
2) or in C6D6 (4); the H and C chemical shifts were
measured relative to the residual proton and carbon
signals of the deuterated solvent; the 19F and 31P
chemical shifts were determined relative to CFCl3 and
85% H3PO4, respectively (external standards). The
elemental analyses were obtained at the Microanalysis
Laboratory (Nesmeyanov Institute of Organoelement
Compounds, Russian Academy of Sciences).
1
1
confirmed by H, H{31P}, 13C{1H}, 19F{1H}, and
31P{1H} NMR spectra.4 In particular, all compounds
1
13
4a–4i characteristically showed in the H and C{1H}
NMR spectra doublet signals in the regions δ 1.48–
1.645 and δC 19.6–20.4 ppm, respectively, due to
methyl group linked to the phosphorus atom. The
phosphorus nucleus resonated at δP 33–36 ppm in the
Phenylphosphonic dichloride (1a, 97%, Acros) and
methylphosphonic dichloride (1b, 98%, Aldrich) were
distilled under reduced pressure prior to use. Phenol
and its mono- and disubstituted derivatives 3a–3i (97–
99%, Acros), anhydrous magnesium chloride (99.9%,
Acros), and magnesium metal (98%, granules, 20–
230 mesh, Aldrich) were used without additional
purification.
2
This procedure provides the best combination of high catalytic
efficiency and convenience in operation, so that the given version
of catalytic synthesis of aryl organylphosphonochloridates seems
to be preferable to the use of anhydrous magnesium chloride.
3
Chlorides 4a and 4b synthesized by classical methods were high-
boiling liquids; both compounds synthesized by catalytic
phosphorylation were crystalline solids.
Signals in the 1H and 13C NMR spectra were assigned using
4
COSY, HMQC, and HMBC shift correlation techniques.
5
These multiplets were converted to singlets in the 1H–{31P} NMR
spectra.
Phenyl phenylphosphonochloridate (2a). Phenyl-
phosphonic dichloride (1a), 40 g (0.205 mol), was
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 88 No. 9 2018

1778
GORYUNOV et al.
3
4
added under argon to 9.7 g (0.102 mol) of phenol, and
0.243 g (0.00256 mol) of finely powdered anhydrous
magnesium chloride was then added. The mixture was
heated for 1.5 h at 120°C until hydrogen chloride no
longer evolved, kept for 0.5 h under reduced pressure
(~15 Torr) at room temperature, and subjected to
fractional distillation under reduced pressure. Yield
17.2 g (66%), bp 154–155°C (0.5 Torr) {bp 152–155°C
(0.3 Torr) [15]}. 31P NMR spectrum: δP 24.1 ppm.
120.6 d (C2, C6, JCP = 5.1), 129.2 d (C3, C5, JCP
=
1.5), 141.7 d (C4, 5JCP = 1.5), 148.0 d (C1, 2JCP = 11.0).
31P NMR spectrum: δP 35.4 ppm. Found, %: C 49.43;
H 5.49; Cl 16.16; P 14.22. C9H12ClO2P. Calculated, %:
C 49.45; H 5.53; Cl 16.22; P 14.17.
4-Isopropylphenyl methylphosphonochloridate (4d).
Yield 66%, bp 101–102°C (0.5 Torr). 1H NMR
3
spectrum, δ, ppm (J, Hz): 1.13 d (6H, CH3CH, JHH
6.8), 1.64 d (3H, CH3P, JHP = 17.2), 2.70 sept (1H,
CH, JHH = 6.9), 7.02–7.08 m (2H, 3-H, 5-H), 7.32–
7.38 m (2H, 2-H, 6-H). C NMR spectrum, δC, ppm
=
2
3
Phenyl methylphosphonochloridate (2b) was
synthesized in a similar way from 47 g (0.5 mol) of
phenol and 200 g (1.5 mol) of molten methylphos-
phonic dichloride (1b) in the presence of 300 mg
(0.0125 mol) of magnesium metal; reaction time 3.0 h.
Yield 86.3 g (91%), bp 107°C (1 Torr) {bp 80°C (0.5
Torr) [16]}. 31P NMR spectrum: δP 36.3 ppm.
13
1
(J, Hz): 19.8 d (CH3P, JCP = 129.1), 23.8 (CH3CH),
33.5 (CH), 120.6 d (C2, C6, 3JCP = 5.1), 127.8 d (C3, C5,
4JCP = 1.5), 146.3 d (C4, 5JCP = 1.5), 148.0 d (C1, 2JCP
=
31
11.0). P NMR spectrum: δP 35.3 ppm. Found, %: C
51.68; H 6.16; Cl 15.22; P 13.32. C10H14ClO2P.
Calculated, %: C 51.63; H 6.06; Cl 15.24; P 13.31.
Aryl methylphosphonochloridates 4a–4i were
synthesized according to analogous procedure from
phosphonic dichloride 1b and mono- and disubstituted
phenols 3a–3i in the presence of magnesium metal as
precatalyst.
4-tert-Butylphenyl methylphosphonochloridate (4e).
Yield 70%, bp 130–131°C (1 Torr). 1H NMR spectrum,
δ, ppm (J, Hz): 1.22 s (9H, CH3C), 1.56 d (3H, CH3P,
2JHP = 17.3), 7.20–7.25 m (2H, 3-H, 5-H), 7.36–7.41 m
13
(2H, 2-H, 6-H). C NMR spectrum, δC, ppm (J, Hz):
1
4-Fluorophenyl methylphosphonochloridate (4a).
Yield 89%, bp 91–92°C (1 Torr), mp 35–37°C {bp 89–
91°C (1 Torr) [5]}. 1H NMR spectrum, δ, ppm (J, Hz):
19.8 d (CH3P, JCP = 129.1), 31.1 (CH3C), 34.1
(CH3C), 120.3 d (C2, C6, JCP = 5.1), 126.8 (C3, C5),
3
147.8 d (C1, JCP = 11.0), 148.5 d (C4, JCP = 1.5). P
NMR spectrum: δP 35.0 ppm. Found, %: C 53.62; H
6.50; Cl 14.24; P 12.57. C11H16ClO2P. Calculated, %:
C 53.56; H 6.54; Cl 14.37; P 12.56.
2
5
31
2
1.52 d (3H, CH3, JHP = 17.3), 6.68–6.77 m (2H, 3-H,
5-H), 7.10–7.17 m (2H, 2-H, 6-H). 13C NMR spectrum,
1
δC, ppm (J, Hz): 19.6 d (CH3, JCP = 128.4), 116.4 d.d
2
4
(C3, C5, JCF = 23.5, JCP = 1.5), 122.3 d.d (C2, C6,
3JCF = 8.1, 3JCP = 5.1), 145.6 d.d (C1, 4JCF = 2.9, 2JCP
=
2-Methoxyphenyl methylphosphonochloridate (4f).
Yield 70%, bp 121–122°C (2 Torr). 1H NMR spectrum,
11.0), 160.3 d.d (C4, JCF = 244.3, JCP = 1.5). 19F
1
5
2
NMR spectrum: δF –116.4 ppm, d (6JFP = 2.5 Hz). P
31
δ, ppm (J, Hz): 1.65 d (3H, CH3P, JHP = 17.3), 3.38 s
3
4
NMR spectrum: δP 35.5 ppm, d (6JPF = 2.5 Hz).
(3H, CH3O), 6.60 d.d.d (1H, 3-H, JHH = 8.2, JHH
≈
5JHP = 1.1), 6.75 t.d (1H, 5-H, JHH = 7.8, JHH = 1.5),
3
4
6.96 t.d.d (1H, 4-H, 3JHH = 7.8, 4JHH ≈ 6JHP = 1.5), 7.56
4-Chlorophenyl methylphosphonochloridate (4b).
3
4
4
d.d.d (1H, 6-H, JHH = 8.0, JHH ≈ JHP = 1.8). 13C
Yield 66%, bp 129–130°C (1 Torr), mp 36–38°C {bp
1
1
119–121°C (0.14 Torr) [17]}. H NMR spectrum, δ,
NMR spectrum, δC, ppm (J, Hz): 20.1 d (CH3P, JCP
=
2
127.6), 55.3 (CH3O), 113.0 d (C3, JCP = 1.0), 120.8 d
4
ppm (J, Hz): 1.48 d (3H, CH3, JHP = 17.3), 6.98–7.03
m (2H, 3-H, 5-H), 7.04–7.10 m (2H, 2-H, 6-H). 13C
(C5, JCP = 2.0), 122.3 d (C6, JCP = 3.9), 126.5 d (C4,
4
3
1
5JCP = 2.0), 139.2 d (C1, JCP = 11.2), 151.0 d (C2,
2
NMR spectrum, δC, ppm (J, Hz): 19.6 d (CH3, JCP
=
128.4), 122.1 d (C2, C6, JCP = 5.1), 129.9 d (C3, C5,
3
3JCP = 4.9). 31P NMR spectrum: δP 36.3 ppm. Found,
%: C 43.76; H 4.47; P 14.31. C8H10ClO3P. Calculated,
%: C 43.56; H 4.57; P 14.04.
4JCP = 1.5), 131.2 d (C4, 5JCP = 2.2), 148.2 d (C1, 2JCP
11.0). 31P NMR spectrum: δP 35.5 ppm.
=
4-Ethylphenyl methylphosphonochloridate (4c).
4-Methoxyphenyl methylphosphonochloridate
1
1
Yield 77%, bp 99–101°C (1 Torr). H NMR spectrum,
(4g). Yield 79%, bp 131–132°C (1 Torr). H NMR
3
2
δ, ppm (J, Hz): 1.08 t (3H, CH3CH2, JHH = 7.6), 1.59
spectrum, δ, ppm (J, Hz): 1.62 d (3H, CH3P, JHP
=
2
3
d (3H, CH3P, JHP = 17.4), 2.41 q (2H, CH2, JHH
=
17.2), 3.35 s (3H, CH3O), 6.68–6.76 m (2H, 3-H, 5-H),
7.25–7.32 m (2H, 2-H, 6-H). 13C NMR spectrum, δC,
ppm (J, Hz): 19.6 d (CH3P, 1JCP = 128.4), 54.9 (CH3O),
7.5), 6.94–7.01 m (2H, 3-H, 5-H), 7.30–7.36 m (2H,
13
2-H, 6-H). C NMR spectrum, δC, ppm (J, Hz): 15.4
1
4
3
114.9 d (C3, C5, JCP = 1.5), 121.8 d (C2, C6, JCP
=
(CH3CH2), 19.8 d (CH3P, JCP = 129.1), 28.1 (CH2),
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 88 No. 9 2018

ELECTROPHILIC CATALYSIS IN THE SYNTHESIS OF ARYL METHYL-
1779
5.1), 143.4 d (C1, 2JCP = 11.0), 157.6 d (C4, 5JCP = 1.5).
31P NMR spectrum: δP 33.8 ppm. Found, %: C 43.59;
H 4.70; Cl 16.23; P 14.04. C8H10ClO3P. Calculated, %:
C 43.56; H 4.57; Cl 16.07; P 14.04.
Kagramanov, N.D., Goryunova, I.B., and Nifant’ev, E.E.,
Russ. Chem. Bull., Int. Ed., 2009, vol. 58, no. 7, p. 1445.
doi 10.1007/s11172-009-0194-0
3. Nguyen, C., Lee, M., and Kim, J., Polym. Adv. Technol.,
2011, vol. 22, no. 5, p. 512. doi 10.1002/pat.1542
4. Nguyen, C. and Kim, J., Macromol. Res., 2008, vol. 16,
2,6-Dimethylphenyl methylphosphonochloridate
1
(4h). Yield 61%, bp 126–127°C (1 Torr). H NMR
no. 7, p. 620. doi 10.1007/BF03218570
2
spectrum, δ, ppm (J, Hz): 1.59 d (3H, CH3P, JHP
=
5. Sharova, E.V., Genkina, G.K., Matveeva, E.V.,
Goryunova, I.B., Goryunov, E.I., Artyushin, O.I., and
Brel, V.K., Russ. Chem. Bull., Int. Ed., 2014, vol. 63,
no. 11, p. 2546. doi 10.1007/s11172-014-0774-5
6. Leonova, E.S., Makarov, M.V., Rybalkina, E.Yu.,
Nayani, S.L., Tongwa, P., Fonari, A., Timofeeva, T.V.,
and Odinets, I.L., Eur. J. Med. Chem., 2010, vol. 45,
no. 12, p. 5926. doi 10.1016/j.ejmech.2010.09.058
7. Makarov, M.V., Leonova, E.S., Rybalkina, E.Yu.,
Tongwa, P., Khrustalev, V.N., Timofeeva, T.V., and
Odinets, I.L., Eur. J. Med. Chem., 2010, vol. 45, no. 3,
p. 992. doi 10.1016/j.ejmech.2009.11.041
8. Odinets, I.L., Makarov, M.V., Artyushin, O.I.,
Rybalkina, E.Yu., Lyssenko, K.A., Timofeeva, T.V., and
Antipin, M.Yu., Phosphorus, Sulfur Silicon Relat.
Elem., 2008, vol. 183, nos. 2–3, p. 619. doi
10.1080/10426500701793246
9. Odinets, I.L., Artyushin, O.I., Goryunov, E.I., Lyssen-
ko, K.A., Rybalkina, E.Yu., Kosilkin, I.V., Timofeeva, T.V.,
and Antipin, M.Yu., Heteroatom Chem., 2005, vol. 16,
no. 6, p. 497. doi 10.1002/hc.20147
10. Reddy, P.M., Viragh, C., and Kovach, I.M., Phosphorus,
Sulfur Silicon Relat. Elem., 2002, vol. 177, nos. 6–7,
p. 1597. doi 10.1080/10426500212239
5
17.1), 2.37 d (6H, 2-CH3, 6-CH3, JHP = 1.0), 6.92 br.s
13
(3H, C6H3). C NMR spectrum, δC, ppm (J, Hz): 17.7
4
1
d (2-CH3, 6-CH3, JCP = 0.7), 20.4 d (CH3P, JCP
129.1), 125.7 d (C4, 5JCP = 2.2), 129.3 d (C3, C5, 4JCP
=
=
=
3
2
2.2), 130.2 d (C2, C6, JCP = 3.7), 148.5 d (C1, JCP
31
12.5). P NMR spectrum: δP 34.4 ppm. Found, %: C
49.48; H 5.57; Cl 15.98; P 14.19. C9H12ClO2P.
Calculated, %: C 49.45; H 5.53; Cl 16.22; P 14.17.
2-Chloro-5-methylphenyl
methylphosphono-
chloridate (4i). Yield 72%, bp 115–116°C (0.1 Torr).
1H NMR spectrum, δ, ppm (J, Hz): 1.48 d (3H, CH3P,
2JHP = 17.2), 2.06 s (3H, 5-CH3), 7.00 d.d.d (1H, 4-H,
4
6
3
3JHH = 8.7, JHH = 2.8, JH4P = 1.8), 7.08 d (3-H, JHH
=
8.6), 7.16 d.d (1H, 6-H, JHH = 2.6, JHP = 1.9). 13C
4
NMR spectrum, δC, ppm (J, Hz): 19.7 (5-CH3), 19.8 d
1
5
(CH3P, JCP = 128.1), 119.6 d (C4, JCP = 5.2), 123.2 d
(C6, JCP = 5.2), 130.1 d (C3, JCP = 1.4), 131.4 d (C5,
3
4
4JCP = 2.1), 138.0 d (C2, 3JCP = 1.4), 148.2 d (C1, 2JCP
=
10.8). 31P NMR spectrum: δP 35.8 ppm. Found, %: C
40.61; H 3.98; Cl 29.95; P 13.53. C8H9Cl2O2P.
Calculated, %: C 40.20; H 3.80; Cl 29.66; P 12.96.
11. El Mastri, M. and Berlin, K.D., Org. Prep. Proced. Int.,
1995, vol. 27, no. 2, p. 161. doi 10.1080/
00304949509458450
12. Kluger, R., Thatcher, G.R.J., and Stallings, W.C., Can.
J. Chem., 1987, vol. 65, no. 8, p. 1838. doi 10.1139/v87-
309
ACKNOWLEDGMENTS
The authors thank Molecular Structure Research
Center (Nesmeyanov Institute of Organoelement
Compounds, Russian Academy of Sciences) for
performing spectral studies.
13. Gefter, E.L., Zh. Obshch. Khim., 1961, vol. 31, no. 10,
p. 3316.
CONFLICT OF INTERESTS
No conflict of interests was declared by the authors.
REFERENCES
14. Kabachnik, M.I., Zakharov, L.S., Goryunov, E.I.,
Kudryavtsev, I.Yu., Molchanova, G.N., Kurykin, M.A.,
Petrovskii, P.V., Shcherbina, T.M., and Laretina, A.P.,
Russ. J. Gen. Chem., 1994, vol. 64, no. 6, p. 812.
15. Marsi, K.L., Van der Werf, C.A., and McEwen, W.E.,
J. Am. Chem. Soc., 1956, vol. 78, no. 13, p. 3063. doi
10.1021/ja01594a032
16. Hudson, R.F. and Keay, L., J. Chem. Soc., 1960, no. 4,
p. 1859. doi 10.1039/JR9600001859
17. Mel’nikov, N.N., Grapov, A.F., and Lebedeva, N.V.,
1. Goryunov, E.I., Baulina, T.V., Goryunova, I.B.,
Matveeva, A.G., Safiulina, A.M., and Nifant’ev, E.E.,
Russ. Chem. Bull., Int. Ed., 2014, vol. 63, no. 1, p. 141.
doi 10.1007/s11172-014-0408-y
Zh. Obshch. Khim., 1966, vol. 36, no. 3, p. 457.
2. Lemport, P.S., Goryunov, E.I., Vologzhanina, A.V.,
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 88 No. 9 2018