Synthesis of 5-substituted 3-(2-oxopropyl)tetrahydrofuran-2-ones and heterocyclic compounds on their base

Article abstract of DOI:10.1134/S1070428008120130

Alkylation of ethyl 2-oxotetrahydrofuran-3-carboxylates with 2,3-dichloroprop-1-ene and 3-bromoprop-1-yne gave new 3,5,5-tri- and 3,3,5,5-tetrasubstituted tetrahydrofuran-2-ones which were converted into the corresponding 3-(2-oxopropyl)tetrahydrofuran-2-ones. Reactions of the latter with semicarabazide, thiosemicarbazide, and phenylhydrazine were studied with a view to obtain new heterocyclic lactones.

Full text of DOI:10.1134/S1070428008120130

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2008, Vol. 44, No. 12, pp. 1799–1803. © Pleiades Publishing, Ltd., 2008.
Original Russian Text © T.V. Kochikyan, E.V. Arutyunyan, V.S. Arutyunyan, A.A. Avetisyan, 2008, published in Zhurnal Organicheskoi Khimii, 2008, Vol. 44,
No. 12, pp. 1826–1830.
Synthesis of 5-Substituted 3-(2-Oxopropyl)tetrahydrofuran-
2-ones and Heterocyclic Compounds on Their Base
T. V. Kochikyan, E. V. Arutyunyan, V. S. Arutyunyan, and A. A. Avetisyan
Erevan State University, ul. Aleka Manukyana 1, Erevan, 375025 Armenia
e-mail: edgarhar2002@mail.ru
Received April 25, 2007
Abstract—Alkylation of ethyl 2-oxotetrahydrofuran-3-carboxylates with 2,3-dichloroprop-1-ene and 3-bromo-
prop-1-yne gave new 3,5,5-tri- and 3,3,5,5-tetrasubstituted tetrahydrofuran-2-ones which were converted into
the corresponding 3-(2-oxopropyl)tetrahydrofuran-2-ones. Reactions of the latter with semicarabazide, thio-
semicarbazide, and phenylhydrazine were studied with a view to obtain new heterocyclic lactones.
DOI: 10.1134/S1070428008120130
It is known that oxo lactones are convenient start-
ing materials for the synthesis of various heterocyclic
compounds. In particular, thiazolyl- and triazolyl-sub-
stituted lactones [1, 2] and indolyl lactones possessing
cardiovascular activity [3, 4] were prepared, etc.
hydrolysis, and optimal conditions for the formation of
functionally substituted lactones IIIa and IIIb were
found. It is advisable to perform the reaction in con-
centrated sulfuric acid (96%). At a lower concentration
of sulfuric acid, the yield of compounds IIIa and IIIb
decreased as a result of concurrent hydrolysis of the
ester moiety. Compounds IIIa and IIIb were also ob-
tained by the Kucherov hydration of acetylenic deriva-
tives IIc and IId.
We have developed a general procedure for the syn-
thesis of 5-substituted 3-(2-oxopropyl)tetrahydrofuran-
2-ones IIIa–IIId starting from ethyl 2-oxotetrahydro-
furan-3-carboxylates Ia and Ib (Scheme 1). Com-
pounds Ia and Ib are fairly strong heterocyclic CH
acids [5–7] and are capable of undergoing alkylation
with halogen derivatives. As alkylating agents we used
2,3-dichloroprop-1-ene and 3-bromoprop-1-yne. The
alkylation was performed in anhydrous ethanol in the
presence of an equimolar amount of sodium ethoxide.
The yields of alkylation products IIa–IId were 80–
88%. Compounds IIa and IIb were subjected to acid
Alkaline hydrolysis of IIa–IId, followed by decar-
boxylation, gave 5-substituted 3-oxo-(2-chloroprop-2-
en-1-yl)- and -3-(prop-2-yn-1-yl)tetrahydrofuran-2-
ones IVa–IVd in 73–80% yield (Scheme 2). Com-
pounds IVa–IVd were subjected to hydrolysis accord-
ing to the procedures described above for IIa–IId; as
a result, 5-substituted 3-(2-oxopropyl)tetrahydrofuran-
2-ones Va and Vb were isolated. Compounds IIIa,
Scheme 1.
COOEt
CH2
ClCH2C(Cl)=CH2
H2SO4
Me
Cl
O
O
IIa, IIb
R
COOEt
O
COOEt
O
Me
Me
Me
COOEt
O
O
O
R
R
BrCH2C CH
≡
H2O, Hg2+
Ia, Ib
IIIa, IIIb
CH
Me
O
O
R
IIc, IId
R = H (a, c), Me (b, d).
1799

KOCHIKYAN et al.
1800
Scheme 2.
CH2
OH–
Cl
H2SO4
IIa, IIb
Me
O
O
Me
R
IVa, IVb
O
Me
O
O
CH
R
H2O, Hg2+
OH–
Va, Vb
IIc, IId
Me
O
O
R
IVc, IVd
R = H (a, c), Me (b, d).
Scheme 3.
R'
Me
X
H2NC(=X)NHNH2
IIIa, IIIb, Va, Vb
Me
N
O
N
Me
O
R
H
VIa–VIh
X = O, R = H, R′ = EtOCO (a), H (c); R = Me, R′ = EtOCO (b), H (d); X = S, R′ = EtOCO, R = H (e), Me (f);
R′ = H, R = H (g), R = Me (h).
IIIb, Va, and Vb readily reacted with semicarbazide
and thiosemicarbazide to afford the corresponding
semicarbazones and thiosemicarbazones VIa–VIf
(Scheme 3).
ic synthesis. For example, compounds VIe and VIf
smoothly reacted with bromoacetophenone to produce
new heterocyclic lactones, (4-phenylthiazol-2-yl)hy-
drazone hydrobromides VIIa and VIIb; treatment of
the latter with aqueous ammonia gave the correspond-
ing free bases VIIIa and VIIIb (Scheme 4).
Thiosemicarbazones attract interest from the prac-
tical viewpoint; it is known that some their analogs
exhibit antimutagenic activity [8]; in addition, thio-
semicarbazones are convenient reagents for fine organ-
With a view to obtain indole derivatives, com-
pounds Va and Vb were treated with phenylhydrazine
Scheme 4.
Me
Me
S
S
Me
Me
PhC(O)CH2Br
NH3–H2O
Ph
· HBr
Ph
VIe, VIf
R
N
R
N
O
O
N
N
N
H
N
O
O
H
VIIa, VIIb
VIIIa, VIIIb
R = H (a), Me (b).
Scheme 5.
Me
NH
PhNHNH2 ·HCl
Va, Vb
Me
R
O
O
IXa, IXb
R = H (a), Me (b).
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 44 No. 12 2008

SYNTHESIS OF 5-SUBSTITUTED 3-(2-OXOPROPYL)TETRAHYDROFURAN-2-ONES
1801
hydrochloride. As a result, we isolated 70–73% of
5-substituted 3-(2-methyl-1H-indol-3-yl)tetrahydrofur-
an-2-ones IXa and IXb (Scheme 5). Preliminarily tests
showed that indolyl-substituted lactones IXa and IXb
exhibit hypotensive and membrane excitation effects.
All the isolated compounds were characterized by
of ester IIa. Found, %: C 55.05; H 6.51; Cl 13.48.
C12H17ClO4. Calculated, %: C 55.28; H 6.53; Cl 13.63.
Ethyl 5-methyl-2-oxo-3-(prop-2-yn-1-yl)tetra-
hydrofuran-3-carboxylate (IIc). Yield 83%, bp 94–
96°C (1 mm), Rf 0.48 (A), nD20 = 1.4605, d420 = 1.1063.
IR spectrum, ν, cm–1: 1770 (C=O, lactone), 1730 (C=O,
ester), 1230 (C–O–C), 2130 (C≡C). Found, %: C 62.66;
H 6.70. C11H14O4. Calculated, %: C 62.85; H 6.67.
1
physical constants and IR and H NMR spectra, and
their purity was checked by TLC.
Ethyl 5,5-dimethyl-2-oxo-3-(prop-2-yn-1-yl)-
EXPERIMENTAL
tetrahydrofuran-3-carboxylate (IId). Yield 85%,
bp 97–98°C (1 mm), Rf 0.45 (A), nD20 = 1.4610, d420
=
1
The H NMR spectra were recorded from solutions
1.0852. The IR spectrum of IId was analogous to that
of IIc. Found, %: C 64.00; H 7.10. C12H16O4. Calculat-
ed, %: C 64.28; H 7.14.
in CDCl3 on a Varian Mercury-300 spectrometer
(300 MHz). The IR spectra were measured from thin
films or suspensions in mineral oil on a Nicolet FTIR
NEXUS instrument. Thin-layer chromatography was
performed on Silufol UV-254 plates using ethanol–
benzene–hexane (3:3:10, A) or ethanol–benzene (1:5,
B) as eluent; development with iodine vapor. The melt-
ing points were determined on a Boetius melting point
apparatus.
Ethyl 2-oxo-3-(2-oxopropyl)tetrahydrofuran-3-
carboxylates IIIa and IIIb (general procedure). Con-
centrated sulfuric acid (96%), 14 ml, was added drop-
wise to 0.05 mol of compound IIa or IIb at such a rate
that the temperature did not exceed 20°C. The mixture
was stirred until hydrogen chloride no longer evolved
(12–13 h), poured into ice water, and extracted with
diethyl ether, the extract was washed with water and
dried over anhydrous magnesium sulfate, the solvent
was removed, and the residue was distilled under
reduced pressure. IR spectrum, ν, cm–1: 1775 (C=O,
lactone); 1710 (C=O, ketone); 1730 (C=O, ester);
1140, 1180 (C–O–C).
Initial ethyl 2-oxotetrahydrofuran-3-carboxylates Ia
and Ib were synthesized according to the procedure
described in [9].
Ethyl 5-methyl-2-oxotetrahydrofuran-3-carbox-
ylates IIa–IId (general procedure). Lactone Ia or Ib,
0.5 mol, was added dropwise to a solution of 11.5 g
(0.5 mol) of metallic sodium in 400 ml of anhydrous
ethanol. The mixture was stirred for 0.5 h, 0.55 mol of
2,3-dichloroprop-1-ene or 3-bromoprop-1-yne was
added, and the mixture was stirred for 0.5 h and heated
on a water bath until neutral reaction. The solvent was
distilled off, and the residue was cooled and acidified
to pH 2–3 with dilute hydrochloric acid. The product
was extracted into diethyl ether, the extracts were
washed with water and dried over anhydrous magne-
sium sulfate, the solvent was removed, and the residue
was distilled under reduced pressure.
Ethyl 5-methyl-2-oxo-3-(2-oxopropyl)tetrahy-
drofuran-3-carboxylate (IIIa). Yield 60%, bp 119–
120°C (2 mm), Rf 0.45 (A), nD20 = 1.4570, d420 = 1.1433.
Found, %: C 57.75; H 7.00. C11H16O5. Calculated, %:
57.89; H 7.02.
Ethyl 5,5-dimethyl-2-oxo-3-(2-oxopropyl)tetra-
hydrofuran-3-carboxylate (IIIb). Yield 62%,
bp 124°C (2 mm), Rf 0.48 (A), nD20 = 1.4570, d420
=
1.1840. Found, %: C 59.32; H 7.50. C12H18O5. Calcu-
lated, %: C 59.50; H 7.44.
Ethyl 3-(2-chloroprop-2-en-1-yl)-5-methyl-2-oxo-
tetrahydrofuran-3-carboxylate (IIa). Yield 80%,
bp 109–110°C (1 mm), Rf 0.49 (A), nD20 = 1.4700, d420 =
1.1745. IR spectrum, ν, cm–1: 1770 (C=O, lactone),
1730 (C=O, ester), 1230 (C–O–C), 1640 (C=C), 3050
(=C–H), 780 (C–Cl). Found, %: C 53.44; H 6.00;
Cl 14.21. C11H15ClO4. Calculated, %: C 53.66; H 6.08;
Cl 14.40.
3-Substituted 5-methyltetrahydrofuran-2-ones
IVa–IVd (general procedure). Compound IIa–IId,
0.1 mol, was added dropwise to 12 g (0.3 mol) of 30%
aqueous sodium hydroxide, and the mixture was stirred
for 0.5 h at room temperature and for 2 h on heating on
a boiling water bath. The mixture was cooled, acidified
to pH 1–2 with concentrated hydrochloric acid, and
extracted with diethyl ether, the extract was washed
with water and dried over anhydrous magnesium sul-
fate, the solvent was distilled off, and the residue was
subjected to decarboxylation. The product was isolated
by vacuum distillation. IR spectrum, ν, cm–1: 1770
Ethyl 3-(2-chloroprop-2-en-1-yl)-5,5-dimethyl-2-
oxotetrahydrofuran-3-carboxylate (IIb). Yield 88%,
bp 111–112°C (1 mm), Rf 0.48 (A), nD20 = 1.4710, d420
=
1.1517. The IR spectrum of IIb was analogous to that
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 44 No. 12 2008

KOCHIKYAN et al.
1802
(C=O, lactone), 1230 (C–O–C); 1640 (C=C), 3050
(=C–H), 2130 (C≡C), 3280 (≡C–H), 780 (C–Cl).
85%, mp 159–161°C, Rf 0.48 (B). Found, %: C 50.45;
H 6.80; N 14.65. C12H19N3O5. Calculated, %: C 50.53;
H 6.67; N 14.74.
5-Methyl 3-(2-chloroprop-2-en-1-yl)tetrahydro-
furan-2-one (IVa). Yield 80%, bp 75°C (2 mm),
Rf 0.47 (A), nD20 = 1.4760, d240 = 1.1449. Found, %:
C 55.00; H 6.30; Cl 20.22. C8H11ClO2. Calculated, %:
C 55.01; H 6.30; Cl 20.34.
Ethyl 5,5-dimethyl-2-oxo-3-(2-semicarbazono-
propyl)tetrahydrofuran-3-carboxylate (VIb). Yield
93%, mp 196–198°C, Rf 0.50 (B). Found, %: C 52.30;
H 7.15; N 13.86. C13H21N3O5. Calculated, %: C 52.17;
H 7.02; N 14.05.
3-(2-Chloroprop-2-en-1-yl)-5,5-dimethyltetra-
hydrofuran-2-one (IVb). Yield 78%, bp 74–75°C
(1 mm), Rf 0.46 (A), nD20 = 1.4725, d420 = 1.1085.
Found, %: C 57.07; H 6.91; Cl 18.68. C9H13ClO2. Cal-
culated, %: C 57.29; H 6.68; Cl 18.83.
5-Methyl-3-(2-semicarbazonopropyl)tetrahydro-
furan-2-one (VIc). Yield 86%, mp 163–164°C, Rf 0.49
(B). Found, %: C 50.60; H 7.15; N 19.65. C9H15N3O3.
Calculated, %: C 50.70; H 7.04; N 19.72.
5-Methyl-3-(prop-2-yn-1-yl)tetrahydrofuran-2-
one (IVc). Yield 73%, bp 69–70°C (1 mm), Rf 0.44
(A), nD20 = 1.4660, d420 = 1.0491. Found, %: C 69.38;
H 7.21. C8H10O2. Calculated, %: C 69.57; H 7.25.
5,5-Dimethyl-3-(2-semicarbazonopropyl)tetra-
hydrofuran-2-one (VId). Yield 92%, mp 188–189°C,
Rf 0.50 (B). IR spectrum, ν, cm–1: 1755 (C=O, lactone);
1180 (C–O–C); 1670 (C=O, amide); 1615 (C=N);
3250, 3175 (NH, NH2). Found, %: C 52.75; H 7.55;
N 18.42. C10H17N3O3. Calculated, %: C 52.86; H 7.42;
N 18.50.
5,5-Dimethyl-3-(prop-2-yn-1-yl)tetrahydrofuran-
2-one (IVd). Yield 75%, bp 97–98°C (2 mm), mp 40–
41°C, Rf 0.46 (A). Found, %: C 71.25; H 7.91. C9H12O2.
Calculated, %: C 71.05; H 7.89.
Thiosemicarbazones VIe–VIh (general proce-
dure). Two drops of concentrated sulfuric acid were
added to a mixture of 40 ml of ethanol, 0.02 mol of the
corresponding lactone, 2 g (0.022 mol) of thiosemi-
carbazide, and 40 ml of water, and the mixture was
heated for 1 h on a boiling water bath. The mixture
was cooled, and the precipitate was filtered off,
washed with water, dried, and recrystallized from
aqueous alcohol.
5-Substituted 3-(2-oxopropyl)tetrahydrofuran-2-
ones Va and Vb (general procedure). Compound IVc
or IVd, 0.1 mol, was added dropwise to a solution of
1.3 g of mercury(II) sulfate in 50 ml of 7% sulfuric
acid at such a rate that the temperature did not exceed
35–40°C. The mixture was stirred for 1 h at 20–25°C
and for 5 h at 60–65°C, cooled, and extracted with
diethyl ether, the extract was washed with water and
dried over anhydrous magnesium sulfate, the solvent
was removed, and the residue was distilled under
reduced pressure.
Ethyl 5-methyl-2-oxo-3-(2-thiosemicarbazono-
propyl)tetrahydrofuran-3-carboxylate (VIe). Yield
90%, mp 172–174°C, Rf 0.55 (B). Found, %: C 47.95;
H 6.20; N 13.72; S 10.45. C12H19N3O4S. Calculated,
%: C 47.84; H 6.31; N 13.95; S 10.63.
5-Methyl-3-(2-oxopropyl)tetrahydrofuran-2-one
(Va). Yield 73%, bp 94–95°C (1 mm), Rf 0.35 (A),
nD20 = 1.4551, d240 = 1.0992. Found, %: C 61.70; H 7.46.
C8H12O3. Calculated, %: 61.53; H 7.69.
Ethyl 5,5-dimethyl-2-oxo-3-(2-thiosemicarba-
zonopropyl)tetrahydrofuran-3-carboxylate (VIf).
Yield 91%, mp 189–191°C, Rf 0.62 (B). Found, %:
C 49.40; H 6.80; N 13.05; S 10.00. C13H21N3O4S. Cal-
culated, %: C 49.52; H 6.67; N 13.33; S 10.16.
5,5-Dimethyl-3-(2-oxopropyl)tetrahydrofuran-2-
one (Vb). Yield 76%, bp 107–108°C (1 mm), Rf 0.41
(A), nD20 = 1.4575, d420 = 1.0869. Found, %: C 63.75;
H 8.10. C9H14O3. Calculated, %: 63.53; H 8.24.
5-Methyl-3-(2-thiosemicarbazonopropyl)tetra-
hydrofuran-2-one (VIg). Yield 81%, mp 153–154°C,
Rf 0.50 (B). Found, %: C 46.30; H 6.45; N 18.57;
S 13.78. C9H15N3O2S. Calculated, %: C 46.16; H 6.55;
N 18.34; S 13.98.
Semicarbazones VIa–VId (general procedure).
A mixture of 0.02 mol of ketone, 2.2 g (0.02 mol) of
semicarbazide hydrochloride, 3.9 g (0.04 mol) of
potassium acetate, and 20 ml of ethanol was heated for
1 h under reflux (on a water bath). The mixture was
cooled and diluted with 30 ml of water. The precipitate
was filtered off, washed with water, dried, and recrys-
tallized from ethanol.
5,5-Dimethyl-3-(2-thiosemicarbazonopropyl)-
tetrahydrofuran-2-one (VIh). Yield 80%, mp 189–
190°C, Rf 0.55 (B). IR spectrum, ν, cm–1: 1755 (C=O,
lactone); 1180 (C–O–C); 1615 (C=N); 3250, 3175 (NH,
NH2). Found, %: C 49.50; H 7.15; N 17.67; S 13.44.
Ethyl 5-methyl-2-oxo-3-(2-semicarbazonopro-
pyl)tetrahydrofuran-3-carboxylate (VIa). Yield
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SYNTHESIS OF 5-SUBSTITUTED 3-(2-OXOPROPYL)TETRAHYDROFURAN-2-ONES
1803
C10H17N3O2S. Calculated, %: C 49.38; H 7.00; N 17.27;
S 13.17.
precipitate was filtered off, washed with water, and
dried. IR spectrum, ν, cm–1: 1770 (C=O, lactone);
1140, 1180 (C–O–C); 1630 (C=Carom); 3080 (=C–H);
1610 (C=Carom); 3400 (NH).
4-Phenylthiazol-2-ylhydrazones VIIIa and VIIIb
(general procedure). Anhydrous acetone, 15 ml, was
added to a mixture of 0.01 mol of thiosemicarbazone
VIe or VIf and 2 g (0.01 mol) of bromoacetophenone.
The mixture was stirred for 0.5 h at 20–25°C and for
1 h on heating under reflux, cooled, and diluted with
30 ml of diethyl ether, and the precipitate was filtered
off, washed with diethyl ether, and dried. The resulting
hydrobromide was placed in a beaker, water was
added, and the mixture was adjusted to pH 9–10 by
adding aqueous ammonia. The precipitate was filtered
off, washed with water, dried, and recrystallized from
aqueous alcohol. IR spectrum, ν, cm–1: 1760 (C=O,
lactone), 1190 (C–O–C), 1540 (C=N), 1610 (C=Carom),
1640 (C=C), 3200 (NH).
5-Methyl-3-(2-methyl-1H-indol-3-yl)tetrahydro-
furan-2-one (IXa). Yield 70%, mp 72–74°C (from
1
water–alcohol, 2:1), Rf 0.48 (A). H NMR spectrum, δ,
ppm: 1.38 s and 1.90 s (3H each, CH3), 2.20–2.80 m
(2H, 4-H), 3.08 m (1H, 3-H), 4.53 d.q (1H, 5-H), 7.10–
7.30 m (4H, C6H4), 9.0 s (1H, NH). Found, %:
C 73.50; H 6.25; N 6.25. C14H15NO2. Calculated, %:
C 73.36; H 6.55; N 6.11.
5,5-Dimethyl-3-(2-methyl-1H-indol-3-yl)tetra-
hydrofuran-2-one (IXb). Yield 73%, mp 68–70°C
1
(from water–alcohol, 2:1), Rf 0.46 (A). H NMR spec-
trum, δ, ppm: 1.31 s and 1.42 s (3H each, CH3), 1.85 s
(3H, CH3), 2.34–2.78 m (2H, 4-H), 3.10 m (1H, 3-H),
7.10–7.15 m and 7.25–7.30 m (2H each, C6H4), 9.10 s
(1H, NH). Found, %: C 73.90; H 7.15; N 5.85.
C15H17NO2. Calculated, %: C 74.07; H 7.00; N 5.76.
5-Methyl-3-[2-(4-phenyl-1,3-thiazol-2-ylhydra-
zono)propyl]tetrahydrofuran-2-one (VIIIa). Yield
80%, mp 136–138°C, Rf 0.39 (B). 1H NMR spectrum,
δ, ppm: 1.34 s (3H, CH3), 1.55 m (1H, 3-H), 1.70 t
(2H, 3-CH2), 1.95 s (3H, CH3), 2.38 d and 2.40 d (1H
each, 4-H), 4.53 d.q (1H, 5-H), 6.75 s (1H, 5′-H),
7.15 t (1H, p-H), 7.27 t (2H, m-H), 7.85 d (2H, o-H),
10.50 s (1H, NH). Found, %: C 62.20; H 5.65;
N 12.95; S 9.90. C17H19N3O2S. Calculated, %: C 62.01;
H 5.76; N 12.77; S 9.73. VIIIa·HBr, mp 192–193°C.
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hydrazono)propyl]tetrahydrofuran-2-one (VIIIb).
Yield 82%, mp 154–156°C, Rf 0.38 (B). H NMR
spectrum, δ, ppm: 1.30 s and 1.45 s (6H, CH3), 1.68 m
(1H, 3-H), 1.74 t (2H, 3-CH2), 1.97 s (3H, CH3), 2.32 d
and 2.38 d (1H each, 4-H), 6.87 s (1H, 5′-H), 7.21 t
(1H, p-H), 7.32 t (2H, m-H), 7.78 d (2H, o-H), 10.53 s
(1H, NH). Found, %: C 63.10; H 6.00; N 12.35;
S 9.55. C18H21N3O2S. Calculated, %: C 62.97; H 6.12;
N 12.24; S 9.33. VIIIb·HBr, mp 197–198°C.
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5,5-Dimethyl-3-(2-methyl-1H-indol-3-yl)tetra-
hydrofuran-2-ones IXa and IXb (general procedure).
A mixture of 0.05 mol of lactone Va or Vb, 7.2 g
(0.05 mol) of phenylhydrazine hydrochloride, 25 ml of
anhydrous ethanol, and 3 ml of concentrated sulfuric
acid was heated for 2 h on a boiling water bath. The
mixture was cooled and diluted with water, and the
9. Arutyunyan, V.S., Kochikyan, T.V., Arutyunyan, E.V.,
and Avetisyan, A.A., Uch. Zap. Erev. Gos. Univ., 2002,
no. 1, p. 73.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 44 No. 12 2008