Efficient methods of synthesis of unsaturated alcohols and ketones by allylation of Favorsky reaction products under phase transfer conditions

Article abstract of DOI:10.1134/S1070428016120034

Allylation of the Favorsky reaction products with allyl halides under phase-transfer catalysis in the system CuI–K₂CO₃–Na₂SO₃–BTEAC–H₂O–C₆H₆afforded the corresponding allylpropar

Full text of DOI:10.1134/S1070428016120034

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2016, Vol. 52, No. 12, pp. 1733–1737. © Pleiades Publishing, Ltd., 2016.
Original Russian Text © V.A. Potapov, T.I. Yaroshenko, V.A. Panov, M.V. Musalov, A.G. Khabibulina, M.V. Musalova, S.V. Amosova, 2016, published in
Zhurnal Organicheskoi Khimii, 2016, Vol. 52, No. 12, pp. 1743–1746.
Efficient Methods of Synthesis of Unsaturated Alcohols
and Ketones by Allylation of Favorsky Reaction Products
under Phase Transfer Conditions
V. A. Potapov, T. I. Yaroshenko, V. A. Panov, M. V. Musalov, A. G. Khabibulina,
M. V. Musalova, and S. V. Amosova*
Favorsky Irkutsk Institute of Chemistry, Siberian Branch, Russian Academy of Sciences,
ul. Favorskogo 1, Irkutsk, 664033 Russia
*e-mail: amosova@irioch.irk.ru
Received August 19, 2016
Abstract—Allylation of the Favorsky reaction products with allyl halides under phase-transfer catalysis in the
system CuI–K2CO3–Na2SO3–BTEAC–H2O–C6H6 afforded the corresponding allylpropargyl alcohols in high
yields (87–96%). The procedure is practical and scalable (more than 50 g of the target product can be prepared
in a single run) and is characterized by high selectivity. Oxidation of secondary allylpropargyl alcohols with
manganese dioxide in anhydrous acetonitrile at room temperature gave 75–81% of allylacetylenic ketones.
DOI: 10.1134/S1070428016120034
Acetylene and its derivatives, in particular Favor-
sky reaction products, are important starting com-
pounds in organic synthesis. Methods of synthesis of
many practically valuable compounds are based on the
use of Favorsky reaction products [1]. The results of
studies on the Favorsky reaction and development of
procedures for the preparation of propargyl alcohols
containing various functional substituents have been
reported in [1–6].
Allylacetylenes possessing both double and triple
carbon–carbon bonds in their molecules could be
promising intermediate products in organic synthesis;
however, their chemical properties have been studied
insufficiently [7–14]. Allylacetylenes were used in syn-
theses of natural compounds, including terpenes [11].
dien-4-yne (diallylacetylene) in 72% yield by cross-
coupling of acetylene with allyl halides in aprotic
solvents (DMF, DMSO, HMPA) under atmospheric
pressure in the presence of a copper salt, base, and
reducing agent [16, 17]. Hept-6-ene-1,3-diyne and
deca-1,9-diene-4,6-diynes were obtained in 85–
90% yield by allylation of diacetylene with allyl
halides [18, 19].
Allylacetylenes containing a hydroxy or carbonyl
functionality can be synthesized by allylation of
propargyl alcohols obtained by the Favorsky reaction.
Many propargyl alcohols are commercially available
and are produced in sufficient amounts by reaction of
acetylene with ketones and aldehydes [1–6].
Development of convenient and efficient proce-
dures for the synthesis of unsaturated alcohols and
ketones via allylation of Favorsky reaction products
under phase-transfer catalysis is a topical problem. By
reacting propargyl alcohols 1–5 with allyl halides at
Allylation of acetylenes in the presence of copper(I)
salts was described in [9–19]. We previously devel-
oped convenient procedures for the synthesis of pent-
1-en-4-yne (allylacetylene, yield >80%) and octa-1,7-
Scheme 1.
CH2
CuI–K2CO3–Na2SO3
BTEAC–H2O–C6H6, 20–25°C
CH
R1
R1
CH2
+
Br
R2
R2
HO
HO
1–5
6–10
1, 6, R1 = R2 = Me; 2, 7, R1R2 = (CH2)5; 3, 8, R1 = H, R2 = Pr; 4, 9, R1 = H, R2 = i-Pr; 5, 10, R1 = H, R2 = Ph.
1733

POTAPOV et al.
1734
Scheme 2.
CH2
CuI–K2CO3–Na2SO3
KI–BTEAC–H2O–C6H6, 75–80°C
CH
R1
R1
CH2
+
Cl
Me
R2
R2
HO
HO
Me
1, 3–5
11–14
3, 11, R1 = H, R2 = Pr; 4, 12, R1 = H, R2 = i-Pr; 5, 13, R1 = H, R2 = Ph; 1, 14, R1 = R2 = Me.
Scheme 3.
CH2
CH2
MnO2, MeCN, 20–25°C
HO
O
R3
R3
R2
R2
10–13
15–18
10, 15, R3 = H, R2 = Ph; 11, 16, R3 = Me, R2 = Pr; 12, 17, R3 = Me, R2 = i-Pr; 13, 18, R3 = Me, R2 = Ph.
room temperature under phase-transfer conditions in
the presence of a base (K2CO3, alkali metal hydrox-
ide), reducing agent (Na2S2O5, Na2SO3, hydrazine
hydrate), and catalytic amount of copper(I) halide
(CuI, CuBr, CuCl) we obtained with high yields (87–
96%) compounds 6–10 (Scheme 1); no inert atmo-
sphere was necessary. The procedure ensured high
selectivity, and allylpropargylic alcohols 6–10 isolated
by extraction from the reaction mixture had a purity of
>96% without additional purification. Allyl bromide
was found to be more effective allylating agent than
allyl chloride.
ment of efficient methods for the preparation of these
compounds makes them accessible and provides the
possibility of detailed study of their chemical prop-
erties and scope of application, in particular in addition
and cyclization reactions with chalcogen-containing
reagents [20].
EXPERIMENTAL
The NMR spectra were recorded from solutions in
CDCl3 on a Bruker DPX-400 spectrometer at 400.13
(1H) and 100.61 MHz (13C) using hexamethyldi-
siloxane as reference. The elemental analyses were
obtained on a Thermo Flash EA1112 analyzer.
Distilled anhydrous acetonitrile was used as solvent in
the oxidation reactions. Compounds 6 and 14 were
described previously [13–15], but their 13C NMR
spectra were not given.
Relatively small amounts of allylpropargylic alco-
hols were obtained by the known methods, and the
yields were lower [12–15]. The procedure developed
by us is experimentally simple, practically feasible,
efficient, and scalable; more than 50 g of the target
product can be obtained in a single run at room tem-
perature from 0.5–1 mol of starting compounds.
Compounds 6–10 (general procedure). A mixture
of 2.76 g (20 mmol) of K2CO3, 1 g (7.9 mmol) of
Na2SO3, 0.5 g (2.6 mmol) of CuI, 0.2 g (0.8 mmol) of
BTEAC, and 15 mL of water was stirred for 5 min,
a solution of 20 mmol of alcohol 1–5 and 3 g
(24.8 mmol) of allyl bromide in 10 mL of benzene
were added, and the mixture was vigorously stirred for
16 h at room temperature. A solution of 4 g of
ammonium chloride in 20 mL of water was added, the
organic layer was separated, and the aqueous phase
was extracted with benzene (2×10 mL). The extracts
were combined with the organic phase and dried over
CaCl2, the solvent was removed on a rotary evaporator,
and the residue was dried under reduced pressure.
When 3-chloro-2-methylprop-1-ene was used
instead of allyl bromide, the yield of the allylation
products decreased to 20–40%. However, raising the
temperature to 75–80°C and adding a catalytic amount
of potassium iodide allowed us to improve the yield of
11–14 to 85–94% (Scheme 2).
Allylacetylenic ketones can be synthesized by
either oxidation of the obtained allylpropargyl alcohols
or allylation of the corresponding ethynyl ketones. The
first approach is more efficient. By oxidation of 10–13
with manganese dioxide in anhydrous acetonitrile at
room temperature we synthesized allylacetylenic
ketones 15–18 in 75–81% yield (Scheme 3). Unsatu-
rated alcohols and ketones 6–18 are promising as
intermediate products in organic synthesis. Develop-
2-Methylhept-6-en-3-yn-2-ol (6). Yield 96%.
1H NMR spectrum, δ, ppm: 1.50 s (6H, CH3), 2.80 s
3
(OH), 2.95 d (2H, =CHCH2, J = 6 Hz), 5.09 d (1H,
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EFFICIENT METHODS OF SYNTHESIS OF UNSATURATED ALCOHOLS
1735
3
3
=CH2, J = 10 Hz), 5.30 d (1H, =CH2, J = 16.9 Hz),
132.55 (CH=). Found, %: C 78.03; H 10.02. C9H14O.
Calculated, %: C 78.21; H 10.21.
5.79 m (1H, =CH). 13C NMR spectrum, δC, ppm: 22.63
(=CHCH2), 31.42 (CH3), 64.93 (COH), 78.55 (≡C),
87.56 (≡C), 115.74 (CH2=), 132.30 (=CH).
1-Phenylhex-5-en-2-yn-1-ol (10). Yield 87%.
1H NMR spectrum, δ, ppm: 2.86 s (1H, OH), 3.07 d
3
3
(2H, =CHCH2, J = 6 Hz), 5.16 (1H, =CH2, J =
Enlarged synthesis of compound 6. A mixture of
69 g (0.5 mol) of K2CO3, 25.2 g (0.2 mmol) of
Na2SO3, 11.4 g (60 mmol) of CuI, 4.56 g (20 mmol) of
benzyl(triethyl)ammonium chloride, and 350 mL of
water was stirred for 30 min, a solution of 42 g
(0.5 mol) of alcohol 1 and 66.6 g (0.55 mol) of allyl
bromide in 250 mL of benzene was added, and the
mixture was vigorously stirred for 68 h at room tem-
perature. A solution of 100 g of ammonium chloride in
500 mL of water was then added, the organic phase
was separated, and the aqueous phase was extracted
with benzene (3×100 mL). The extracts were com-
bined with the organic phase and dried over CaCl2,
the solvent was removed on a rotary evaporator, and
the residue was dried under reduced pressure.
Yield 50.3 g (81%).
3
10 Hz), 5.18 (1H, =CH2, J = 17 Hz), 5.49 m (1H,
OCH), 5.86 m (1H, =CH), 7.32–7.41 m (3H, Ph),
7.56–7.57 (2H, Ph). 13C NMR spectrum, δC, ppm:
22.84 (=CHCH2), 64.05 (CHOH), 82.79 (≡C), 82.87
(≡C), 116.26 (CH2=), 126.17 (Carom), 127.88 (Carom),
127.49 (Carom), 131.64 (CH=), 140.99 (Carom).
Found, %: C 83.43; H 6.85. C12H12O. Calculated, %:
C 83.69; H 7.02.
Compounds 11–14 (general procedure). A mixture
of 2.76 g (20 mmol) of K2CO3, 1 g (7.9 mmol) of
Na2SO3, 0.5 g (2.6 mmol) of CuI, 0.3 g (1.8 mmol) of
KI, 0.2 g (0.8 mmol) of BTEAC, and 15 mL of water
was stirred for 5 min. A solution of 20 mmol of alcohol
1–5 and 2.3 g (25 mmol) of 3-chloro-2-methylprop-1-
ene in 10 mL of benzene was added, and the mixture
was heated for 6 h at 75–80°C under stirring. After
cooling, the mixture was treated with a solution of 4 g
of NH4Cl in 20 mL of water, the organic phase was
separated, and the aqueous phase was extracted with
benzene (2×10 mL). The extracts were combined with
the organic phase and dried over CaCl2, and the sol-
vent was removed on a rotary evaporator.
1-(Pent-4-en-1-yn-1-yl)cyclohexan-1-ol (7). Yield
1
87%. H NMR spectrum, δ, ppm: 1.12–1.22 (2H,
CH2), 1.40–1.52 (4H, CH2), 1.53–1.62 (2H, CH2),
1.73–1.83 (2H, CH2), 2.64 s (OH), 2.89 d (2H,
=CHCH2, J = 6.1 Hz), 5.06 d (1H, =CH2, J =
3
3
3
9.9 Hz), 5.25 d (1H, =CH2, J = 16.9 Hz), 5.75 m
(=CH). 13C NMR spectrum, δC, ppm: 22.81
(=CHCH2), 23.14 (CH2), 24.95 (CH2), 39.91 (CH2),
68.44 (COH), 80.52 (≡C), 87.69 (≡C), 115.68 (=CH2),
132.39 (=CH). Found, %: C 80.14; H 9.63. C11H16O.
Calculated, %: C 80.44; H 9.82.
8-Methylnon-8-en-5-yn-4-ol (11). Yield 85%.
1H NMR spectrum, δ, ppm: 0.86 t (3H, CH3), 1.39 m
(2H, CH2), 1.60 m (2H, CH2), 1.70 s (3H, CH3), 2.84 s
(2H, =CCH2), 2.90 s (OH), 4.28 m (1H, OCH), 4.74 s
and 4.90 s (1H each, =CH2). 13C NMR spectrum, δC,
ppm: 13.38 (CH3), 18.28 (CH2), 21.88 (CH3), 27.46
(=CCH2), 40.01 (HOCHCH2), 62.31 (CHOH), 82.07
(≡C), 83.88 (≡C), 111.73 (CH2=), 140.48 (=C). Found,
%: C 79.12; H 10.73. C10H16O. Calculated, %:
C 78.90; H 10.59.
Non-8-en-5-yn-4-ol (8). Yield 90%. 1H NMR spec-
trum, δ, ppm: 0.91 t (3H, CH3), 1.46 m (2H, CH2),
1.65 m (2H, CH2), 2.49 s (1H, OH), 2.96 d (2H,
3
=CHCH2, J = 6 Hz), 4.36 m (1H, OCH), 5.08 d (1H,
3
3
=CH2, J = 10 Hz), 5.28 d (1H, =CH2, J = 17 Hz),
5.77 m (1H, =CH). 13C NMR spectrum, δC, ppm: 13.55
(CH3), 18.28 (CH3), 22.79 (=CHCH2), 39.94 (CH2),
62.11 (CHOH), 81.37 (≡C), 83.73 (≡C), 115.87
(CH2=), 132.21 (CH=). Found, %: C 78.51; H 10.39.
C9H14O. Calculated, %: C 78.21; H 10.21.
2,7-Dimethyloct-7-en-4-yn-3-ol (12). Yield 90%.
1H NMR spectrum, δ, ppm: 0.90 t (6H, CH3), 1.69 s
(3H, CH3), 1.77 m (1H, CHCH3), 2.83 s (2H, =CCH2),
2.95 s (OH), 4.09 m (1H, OCH), 4.72 s (1H, =CH2),
4.91 s (1H, =CH2). 13C NMR spectrum, δC, ppm: 17.32
(CH3), 18.14 (CH3), 21.85 (CH3), 27.36 (=CCH2),
34.68 (CHCH3), 67.74 (CHOH), 82.35 (≡C), 83.04
(≡C), 111.55 (=CH2), 140.43 (=C). Found, %: C 79.16;
H 10.47. C10H16O. Calculated, %: C 78.90; H 10.59.
2-Methyloct-7-en-4-yn-3-ol (9). Yield 91%.
1H NMR spectrum, δ, ppm: 0.91 d (6H, CH3), 1.78 m
(1H, CHCH3), 2.92 d (2H, =CHCH2, 3J = 6 Hz), 3.01 s
3
(1H, OH), 4.08 m (1H, OCH), 5.02 d (1H, =CH2, J =
10 Hz), 5.25 d (1H, =CH2, J = 17 Hz), 5.73 m (1H,
=CH). 13C NMR spectrum, δC, ppm: 17.49 (CH3),
18.19 (CH3), 22.99 (=CHCH2), 34.59 (CHCH3), 67.64
(CHOH), 81.87 (≡C), 82.66 (≡C), 116.01 (CH2=),
5-Methyl-1-phenylhex-5-en-2-yn-1-ol (13). Yield
1
94%. H NMR spectrum, δ, ppm: 1.83 s (3H, CH3),
3.07 s (2H, =CCH2), 3.42 s (1H, OH), 4.90 m and
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POTAPOV et al.
1736
C 79.81; H 9.23. C10H14O. Calculated, %: C 79.96;
H 9.39.
5.08 m (1H, CH2=), 5.42 s (1H, CHOH), 7.36–7.42 m
(3H, Ph), 7.57–7.61 m (2H, Ph). 13C NMR spectrum,
δC, ppm: 22.19 (CH3), 27.63 (=CCH2), 64.66 (CHOH),
83.91 (≡C), 84.33 (≡C), 112.05 (=CH2), 126.75 (Carom),
128.64 (Carom), 129.06 (Carom), 140.35 (=C), 141.30
(Carom). Found, %: C 83.58; H 7.39. C13H14O. Calcu-
lated, %: C 83.83; H 7.58.
5-Methyl-1-phenylhex-5-en-2-yn-1-one (18).
1
Yield 81%. H NMR spectrum, δ, ppm: 1.85 s (3H,
CH3), 3.08 s (2H, =CCH2), 4.80 s and 4.93 s (1H each,
=CH2), 7.36–7.43 m (2H, Ph), 7.57–7.61 m (1H, Ph),
8.13–8.19 m (2H, Ph). 13C NMR spectrum, δC, ppm:
22.83 (CH3), 28.40 (=CCH2), 81.70 (≡C), 93.43 (≡C),
113.76 (=CH2), 129.71 (Carom), 130.33 (Carom), 134.78
(=CH), 136.92 (Carom), 138.52 (Carom), 178.25 (C=O).
Found, %: C 84.58; H 6.37. C13H12O. Calculated, %:
C 84.75; H 6.57.
2,6-Dimethylhept-6-en-3-yn-2-ol (14). Yield 92%.
1H NMR spectrum, δ, ppm: 1.47 s (6H, CH3), 1.73 s
(3H, CH3), 2.67 s (1H, OH), 2.85 s (2H, =CCH2),
4.78 s (1H, =CH2), 4.95 s (1H, =CH2). 13C NMR spec-
trum, δC, ppm: 21.96 (CH3), 27.27 (=CCH2), 31.60
(CH3), 65.12 (CHOH), 79.25 (≡C), 87.70 (≡C), 111.55
(=CH2), 140.40 (=C).
This study was performed under financial support
by the Russian Science Foundation (project no. 14-13-
01 085). The spectral measurements were carried
out using the facilities of the Baikal Joint Analytical
Center, Siberian Branch, Russian Academy of
Sciences.
Compounds 15–18 (general procedure). A mixture
of 5 mmol of compound 10–13, 2 g (23 mmol) of
MnO2, and 20 mL of acetonitrile was vigorously
stirred for 16 h at room temperature. The mixture was
filtered, and the precipitate was washed with
acetonitrile on a filter. The solvent was distilled off
from the filtrate, and the residue was purified by silica
gel chromatography using hexane–chloroform (8:1)
as eluent.
REFERENCES
1. Trofimov, B.A. and Shmidt, E.Yu., Russ. Chem. Rev.,
2014, vol. 83, p. 600.
2. Ivanov, A.V., Shcherbakova, V.S., Ushakov, I.A.,
Sobenina, L.N., Petrova, O.N., Mikhaleva, A.I., and
Trofimov, B.A., Beilstein J. Org. Chem., 2015, vol. 11,
p. 228.
3. Schmidt, E.Yu., Cherimichkina, N.A., Bidusenko, I.A.,
Protsuk, N.I., and Trofimov, B.A., Eur. J. Org Chem.,
2014, p. 4663.
4. Shmidt, E.Yu., Bidusenko, I.A., Protsuk, N.I., Mikha-
leva, A.I., and Trofimov, B.A., Russ. J. Org. Chem.,
2013, vol. 49, p. 8.
5. Sobenina, L.N., Tomilin, D.N., Petrova, O.V., Mikha-
leva, A.I., and Trofimov, B.A., Russ. J. Org. Chem.,
2013, vol. 49, p. 356.
1-Phenylhex-5-en-2-yn-1-one (15). Yield 80%.
1H NMR spectrum, δ, ppm: 3.25 d (2H, =CHCH2, 3J =
6 Hz), 5.21 d (1H, =CH2, 3J = 10 Hz), 5.40 d (1H, 3J =
17 Hz), 5.87 m (1H, =CH), 7.42–7.50 m (2H, Ph),
7.54–7.60 m (1H, Ph), 8.10–8.16 m (2H, Ph).
13C NMR spectrum, δC, ppm: 23.41 (=CHCH2), 81.32
(≡C), 92.51 (≡C), 113.70 (=CH2), 128.51 (Carom),
129.53 (Carom), 130.09 (Carom), 134.04 (=CH), 136.83
(Carom), 177.95 (C=O). Found, %: C 84.93; H 6.09.
C12H10O. Calculated, %: C 84.68; H 5.92.
8-Methylnon-8-en-5-yn-4-one (16). Yield 76%.
1H NMR spectrum, δ, ppm: 0.86 t (3H, CH3), 1.61 m
(2H, CH2), 1.81 s (3H, CH3), 2.45 t (CH2C=O), 3.00 s
(2H, =CCH2), 4.81 s and 4.91 s (1H each, CH2=).
13C NMR spectrum, δC, ppm: 13.30 (CH3), 17.43
(CH2), 21.87 (CH3), 27.37 (=CCH2), 47.23 (CH2C=O),
82.39 (≡C), 90.63 (≡C), 112.78 (=CH2), 138.19 (=C),
188.26 (C=O). Found, %: C 80.15; H 9.57. C10H14O.
Calculated, %: C 79.96; H 9.39.
6. Tomilin, D.N., Petrova, O.V., Sobenina, L.N., Mikha-
leva, A.I., and Trofimov, B.A., Chem. Heterocycl.
Compd., 2013, vol. 49, p. 341.
7. Bumagin, N.A., Russ. Chem. Bull., 1996, vol. 45,
p. 2031.
8. Dzhemilev, U.M., Ibragimov, A.G., and Saraev, R.A.,
Bull., Acad. Sci. USSR, Div. Chem. Sci., 1986, vol. 35,
p. 397.
9. Temkin, O.N., Shestakov, G.K., and Treger, Yu.A.,
Atsetilen. Khimiya. Mekhanizmy reaktsii. Tekhnologiya
(Acetylene. Chemistry. Reaction Mechanisms. Technol-
ogy), Moscow: Khimiya, 1991, p. 216.
10. Grushin, V.V. and Alper, H., J. Org. Chem., 1992,
vol. 57, p. 2188.
11. Mignani, G., Chevalier, C., Grass, F., Allmang, G., and
2,7-Dimethyloct-7-en-4-yn-3-one (17). Yield 75%.
1H NMR spectrum, δ, ppm: 1.06 d (6H, CH3), 1.69 s
(3H, CH3), 2.51 m (1H, CHC=O), 2.97 s (2H, =CCH2),
4.77 s and 4.88 s (1H each, CH2=). 13C NMR spec-
trum, δC, ppm: 18.02 (CH3), 22.64 (CH3), 27.69
(=CCH2), 43.13 (CHC=O), 81.61 (≡C), 91.78 (≡C),
113.04 (=CH2), 138.52 (=C), 192.46 (C=O). Found, %:
Morel, D., Tetrahedron Lett., 1990, vol. 31, p. 5161.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 52 No. 12 2016

EFFICIENT METHODS OF SYNTHESIS OF UNSATURATED ALCOHOLS
1737
12. Sevin, A., Chodkiewicz, W., and Cadiot, P., Bull. Soc.
Chim. Fr., 1974, p. 913.
13. Jeffery, T., Tetrahedron Lett., 1989, vol. 30, p. 2225.
17. Potapov, V.A., Musalov, M.V., Panov, V.A., Musalo-
va, M.V., and Amosova, S.V., Russ. J. Org. Chem.,
2013, vol. 49, p. 1834.
18. Musalov, M.V., Potapov, V.A., Musalova, M.V., and
Amosova, S.V., Russ. J. Org. Chem., 2014, vol. 50,
p. 898.
14. Veliev, M.G., Shatirova, M.I., Chalabiev, Ch.A.,
Mamedov, I.M., and Mustafaev, A.M., Russ. J. Org.
Chem., 1995, vol. 31, p. 52.
19. Musalov, M.V., Potapov, V.A., Musalova, M.V., and
Amosova, S.V., Russ. Chem. Bull., Int. Ed., 2015,
vol. 64, p. 2273.
15. Bieber, L.W. and da Silva, M.F., Tetrahedron Lett.,
2007, vol. 48, p. 7088.
16. Musalov, M.V., Musalova, M.V., Potapov, V.A., and
Amosova, S.V., Russ. Chem. Bull., Int. Ed., 2012,
vol. 61, p. 2007.
20. Potapov, V.A., Musalov, M.V., Musalova, M.V., and
Amosova, S.V., Curr. Org. Chem., 2016, vol. 20, p. 136.
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