Specificity of the reaction of 2,3-dichloro-4,4-dimethoxy-5-(2-methylfuran- 3-yl)cyclopent-2-en-1-one with amines

Article abstract of DOI:10.1134/s1070428008030147

2,3-Dichloro-4,4-dimethoxy-5-(2-methylfuran-3-yl)cyclopent-2-en-1-one reacted with diethyl-and dipropylamines to give products of Ad_NE replacement of the chlorine atom at the vinylic C³ atom and substitutive opening of the furan ring

Full text of DOI:10.1134/s1070428008030147

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2008, Vol. 44, No. 3, pp. 397–401. © Pleiades Publishing, Ltd., 2008.
Original Russian Text © F.A. Gimalova, E.M. Minnibaeva, E.M. Vyrypaev, M.S. Miftakhov, 2008, published in Zhurnal Organicheskoi Khimii, 2008,
Vol. 44, No. 3, pp. 403–406.
Specificity of the Reaction of 2,3-Dichloro-4,4-dimethoxy-
5-(2-methylfuran-3-yl)cyclopent-2-en-1-one with Amines
F. A. Gimalova, E. M. Minnibaeva, E. M. Vyrypaev, and M. S. Miftakhov
Institute of Organic Chemistry, Ufa Research Center, Russian Academy of Sciences,
pr. Oktyabrya 71, Ufa, 450054 Bashkortostan, Russia
e-mail: bioreg@anrb.ru
Received March 30, 2007
Abstract—2,3-Dichloro-4,4-dimethoxy-5-(2-methylfuran-3-yl)cyclopent-2-en-1-one reacted with diethyl- and
dipropylamines to give products of AdNE replacement of the chlorine atom at the vinylic C3 atom and
substitutive opening of the furan ring with simultaneous deprotection of the dimethyl acetal moiety in the
2,3-dichlorocyclopentenone fragment.
DOI: 10.1134/S1070428008030147
While attempting to generate anionoid interme-
diates from the furan fragment of trichlorocyclopente-
none I [1] by the action of lithium diisopropylamide
(tetrahydrofuran, –78°C) we revealed smooth selective
reductive dechlorination at the C5–Cl bond with forma-
tion of dichlorocyclopentenone II (Scheme 1). The
same compound was obtained later by treatment of tri-
chlorocyclopentenone I with CrCl2 [2], as well as by
the action of zinc in methanol in the presence of am-
monium chloride (in a poor yield).
ethylamine differed from the behavior of trichloro
derivative I. We isolated two main products at a ratio
of ~2:1. On the basis of spectral data, they were as-
signed structures IV and V (minor product). Likewise,
the reaction of II with dipropylamine gave a mixture
of compounds VI and VII (Scheme 3).
Scheme 2.
Cl
O
Me
Et2NH, MeOH, 20°C
O
I
Et2N
MeO
Scheme 1.
OMe
Cl
O
Cl
O
Me
i, ii, or iii
NEt2
O
III
Cl
Cl
O
Cl
MeO
OMe
MeO
OMe
Me
Scheme 3.
I
II
Cl
O
Me
i: (i-Pr)2NLi, THF, –78°C (yield 60%); ii: CrCl2, Me2CO
(68%); iii: Zn, NH4Cl, MeOH (20%).
R2NH, MeOH, 20°C
II
R2N
O
MeO
OMe
IV, VI
We previously described reactions of trichlorocy-
clopentenone I with secondary amines, such as diethyl-
amine, morpholine, pyrrolidine, dipropylamine, etc.
These reactions afforded unusual products of substi-
tutive opening of the furan ring. For example, com-
pound III was formed in the reaction of I with diethyl-
amine [3] (Scheme 2).
O
Me
Cl
Cl
O
+
NR2
O
Dichloride II obtained from trichlorocyclopente-
none I was also brought into reactions with amines.
However, the behavior of II in the reaction with di-
V, VII
IV, V, R = Et; VI, VII, R = Pr.
397

GIMALOVA et al.
398
On the other hand, no cross-conjugated triketones
triketones V and VII is determined by the following
factors: first, diethyl- and dipropylamines can be
regarded as somewhat stronger and less sterically
hindered nucleophiles than the other amines involved;
second, structural specificity of compound II related
to the absence of chlorine on C5 (unlike trichloro
ketone I) makes it capable of undergoing enolization
during the process.
like V and VII were formed in the reactions of di-
chlorocyclopentenone II with morpholine, pyrrolidine,
and dimethylamine. In these cases, we isolated in good
yields the expected AdNE replacement products [4] at
the C3–Cl bond, i.e., cyclic vinylogous amides VIII,
IX, and XII that are structurally related to compounds
IV and VI. Furthermore, unlike trichlorocyclopente-
none I, dichloro ketone II reacted fairly smoothly with
primary amines. Its reactions with benzylamine,
α-methylbenzylamine, and methylamine led to the
formation of products X, XI, and XIII as a result of
replacement of the chlorine atom on C3 (Scheme 4).
EXPERIMENTAL
The IR spectra were recorded on Specord M-80 and
UR-20 spectrophotometers from samples prepared as
thin films (neat) or dispersed in Nujol. The NMR spec-
tra were measured on a Bruker AM-300 instrument at
Scheme 4.
1
300 MHz for H and 75.47 MHz for 13C using CDCl3
Cl
O
RR'NH or RR'NH· HCl
MeOH
Me
as solvent and tetramethylsilane as internal reference.
The mass spectra (electron impact, 70 eV) were ob-
tained on Shimadzu LCMS-2010 and Thermo Finnigan
MAT 95XP spectrometers; ion source temperature
200°C, batch inlet probe temperature 5–270°C, tem-
perature ramp 22 deg/min. Thin-layer chromatography
was performed on Silufol and Sorbfil plates; spots
were detected by treatment with iodine vapor or by
spraying with a solution of p-methoxybenzaldehyde
and sulfuric acid in ethanol and subsequent heating at
120–150°C. The products were isolated by column
chromatography on silica gel L (200–280 μm, Russia)
using 30–60 g of the sorbent per gram of substrate;
freshly distilled solvents were used as eluents. Liquid
amines were purified by drying over powdered potas-
sium hydroxide, followed by distillation.
II
RR'N
MeO
O
OMe
VIII–XIII
VIII, RR′N = morpholino; IX, RR′ = (CH2)4; X, R = H,
R′ = PhCH2; XI, R = H, R′ = PhCH(Me); XII, R = R′ = Me;
XIII, R = H, R′ = Me.
Unexpectedly, the major product formed in the
reaction of II with diisopropylamine in methanol was
trimethoxy derivative XIV which was isolated as
a mixture with expected 3-substituted ketone XV at
1
a ratio of ~3:1 (according to the H NMR data). Pre-
sumably, the reaction of less active dichloro derivative
II with methanol to give compound XIV competes
with the reaction with sterically loaded diisopropyl-
amine (Scheme 5).
2,3-Dichloro-4,4-dimethoxy-5-(2-methylfuran-3-
yl)cyclopent-2-en-1-one (II). Compound I, 0.28 g
(0.86 mmol), was dissolved in 10 ml of acetone, 20 ml
of a freshly prepared solution of CrCl2 was added
under stirring, and the mixture was stirred for ~1 h at
room temperature. Acetone was evaporated, the aque-
ous phase was extracted with chloroform (3×10 ml),
the extracts were combined, washed with a solution of
sodium chloride, dried over MgSO4, and evaporated,
and the residue was purified by column chromatog-
raphy on silica gel using ethyl acetate–petroleum ether
(1:9) as eluent. Yield 0.14 g (68%), colorless crystals,
Scheme 5.
Cl
O
Me
(i-Pr)2NH, MeOH, 20°C
II
MeO
MeO
O
OMe
XIV
Cl
O
Me
+
(i-Pr)2N
O
1
mp 96–98°C. H NMR spectrum, δ, ppm: 2.24 s (3H,
MeO
OMe
CH3), 3.35 s (3H) and 3.43 s (3H, OCH3), 3.88 s (1H,
5-H), 6.15 d (1H, 4′-H, J = 1.9 Hz), 7.26 d (1H, 5′-H,
J = 1.9 Hz). 13C NMR spectrum, δC, ppm: 11.94 (CH3),
51.38 and 51.51 (OCH3), 54.74 (C5), 102.49 (C4),
111.53 (C2), 111.35 (C4′), 134.81 (C3′), 140.34 (C5′),
150.49 (C2′), 158.49 (C3), 192.14 (C=O). Found, %:
XV
Among the examined reactions of dichloro ketone
II with diethyl- and dipropylamines, the formation of
cyclopentene triketones V and VII attracts undoubted
interest. Presumably, the reaction direction leading to
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SPECIFICITY OF THE REACTION OF 2,3-DICHLORO-4,4-DIMETHOXY-...
399
C 50.03; H 4.50; Cl 23.96. C12H12Cl2O4. Calculated,
%: C 49.51; H 4.15; Cl 24.36.
0.08 g (~48%), oily substance. 1H NMR spectrum, δ,
ppm: 0.93 t (6H, CH3, J = 7.4 Hz), 1.67 m (4H, CH2,
J = 7.4 Hz), 2.28 s (3H, CH3), 3.01 s and 3.32 s (3H
each, OCH3), 3.46 m and 3.89 m (2H each, NCH2),
3.68 s (1H, 5-H), 6.13 d (1H, 4′-H, J = 1.8 Hz), 7.23 d
(1H, 5′-H, J = 1.8 Hz). 13C NMR spectrum, δC, ppm:
10.87 and 11.86 (CH3), 22.35 and 29.63 (CH2), 47.72
(C5), 50.58 and 51.44 (OCH3), 59.35 (CH2N), 103.19
(C4), 106.34 (C2), 111.23 (C4′), 113.59 (C3′), 140.05
(C5′), 149.64 (C2′), 160.18 (C3), 190.63 (C1).
Reaction of compound II with diethylamine.
A solution of 0.3 ml (2.28 mmol) of diethylamine in
5 ml of methanol was added dropwise under stirring to
a solution of 0.22 g (0.76 mmol) of compound II in
5 ml of methanol. The mixture was stirred for 3 h at
room temperature until the initial compound disap-
peared according to the TLC data. The solvent was
evaporated, 10 ml of cold water was added to the
residue, and the mixture was extracted with chloroform
(4×20 ml). The extracts were combined, washed with
a saturated aqueous solution of sodium chloride, dried
over MgSO4, and evaporated. The residue was sub-
jected to column chromatography on silica gel (ethyl
acetate–petroleum ether, 1:4) to isolate 0.09 g (~36%)
of compound IV and 0.040 g (18%) of V.
(5Z)-2,3-Dichloro-5-[(1E)-dipropylamino-4-oxo-
pent-1-en-3-ylidene]cyclopent-2-ene-1,4-dione
1
(VII). Yield 0.04 g (24%), oily substance. H NMR
spectrum, δ, ppm: 0.91 m (6H, CH3), 1.62 m (4H,
CH2), 2.47 s (3H, COCH3), 3.16 s (6H, OCH3), 3.45 m
and 3.82 m (2H each, NCH2), 6.87 d (1H, 4′-H, J =
13.3 Hz), 7.05 d (1H, 5′-H, J = 13.3 Hz). 13C NMR
spectrum, δC, ppm: 11.32 (CH3), 19.99 and 22.13
(CH2), 31.63 (CH3), 58.56 (CH2N), 94.47 (C2′), 106.34
(C5), 137.48 (C2, C3), 151.69 (C1′), 159.26 (C3′), 179.83
and 179. 90 (C1, C4), 204. 09 (C4 ′). Found:
[M]+ 355.1552. C18H23ClNO4. Calculated: M 355.1540.
2-Chloro-3-diethylamino-4,4-dimethoxy-5-(2-
methylfuran-3-yl)cyclopent-2-en-1-one (IV). Light
yellow crystals, mp 78–80°C. IR spectrum, ν, cm–1:
642, 781, 858, 935, 981, 1069, 1098, 1140, 1271,
1
1449, 1578, 1682. H NMR spectrum, δ, ppm: 1.26 t
(6H, CH3, J = 7.0 Hz), 2.27 s (3H, CH3), 3.00 s and
2-Chloro-4,4-dimethoxy-5-(2-methylfuran-3-yl)-
3-morpholinocyclopent-2-en-1-one (VIII) was ob-
tained from 0.1 g (0.34 mmol) of compound VII and
0.12 ml (1.36 mmol) of morpholine. Yield 0.08 g
3.31 s (3H each, OCH3), 3.65 m (2H) and 3.89 q.d
2
3
(2H, NCH2, J = 14.0, J = 7.1 Hz), 3.68 s (1H, 5-H),
6.11 d (1H, 4′-H, J = 1.9 Hz), 7.21 d (1H, 5′-H, J =
1.9 Hz). Mass spectrum: m/z 327 [M]+.
1
(68%), white powder, mp 112–114°C. H NMR spec-
trum, δ, ppm: 2.26 s (3H, CH3), 3.0 s and 3.35 s (3H
each, OCH3), 3.69 s (1H, 5-H), 3.79 m (4H, NCH2),
3.97 m (4H, OCH2), 6.12 d (1H, 4′-H, J = 1.8 Hz),
7.22 d (1H, 5′-H, J = 1.8 Hz). 13C NMR spectrum, δC,
ppm: 11.84 (CH3), 47.79 (C5), 48.93 (CH2N), 50.96
and 51.73 (OCH3), 67.19 (CH2O), 104.01 (C4), 106.31
(C2), 111.08 (C4′), 113.02 (C3′), 140.23 (C5′), 149.85
(C2′), 159.64 (C3), 190.86 (C1). Found, %: C 55.90;
H 6.20; Cl 9.89; N 3.86. C16H20ClNO5. Calculated, %:
C 56.23; H 5.90; Cl 10.37; N 4.10.
(5Z)-2,3-Dichloro-5-[(1E)-diethylamino-4-oxo-
pent-1-en-3-ylidene]cyclopent-2-ene-1,4-dione (V).
Brown needles liquefying on exposure to air at room
temperature. IR spectrum, ν, cm–1: 993, 1078, 1136,
1
1194, 1254, 1439, 1506, 1612, 1661, 1707. H NMR
spectrum, δ, ppm: 1.26 t (3H, CH3, J = 7.0 Hz) and
1.29 t (3H, CH3, J = 7.2 Hz), 2.45 s (3H, COCH3),
3.39 q (2H, J = 7.2 Hz) and 3.45 q (2H, NCH2, J =
7.1 Hz), 6.87 d (1H, 4′-H, J = 13.2 Hz), 7.05 d (1H,
5′-H, J = 13.2 Hz). 13C NMR spectrum, δC, ppm: 11.76
and 14.33 (CH3), 29.11 (CH3), 43.64 and 52.02 (CH2N),
94.39 (C2′), 102.16 (C5), 143.49 (C2), 144.49 (C3),
155.51 (C1′), 159.32 (C3′), 182.54 and 183.64 (C1, C4),
204.09 (C4′). Mass spectrum, m/z (Irel, %): 315, 317,
319 (75) [M]+; 274, 272 (50) [M – CH3CO]+; 244, 246
(100) [M – NEt2]+; [M – CH3CO – NEt2]+ 201, 203.
2-Chloro-4,4-dimethoxy-5-(2-methylfuran-3-yl)-
3-(pyrrolidin-1-yl)cyclopent-2-en-1-one (IX) was ob-
tained from 0.14 g (0.48 mmol) of compound II and
0.16 ml (1.91 mmol) of pyrrolidine. Yield 0.14 g
(89%), light yellow powder, mp 92–94°C. IR spec-
trum, ν, cm–1: 723, 870, 1126, 1231, 1279, 1375, 1395,
1
Compounds VI–VIII, XI, XIV, and XV were syn-
thesized in a similar way.
1582, 1690. H NMR spectrum, δ, ppm: 1.91 (4H,
CH2), 2.27 s (3H, CH3), 3.00 s and 3.32 s (3H each,
OCH3), 3.71 s (1H, 5-H), 3.83 m (2H) and 4.09 m (2H,
NCH2), 6.14 d (1H, 4′-H, J = 1.6 Hz), 7.22 d (1H,
5′-H, J = 1.6 Hz). 13C NMR spectrum, δC, ppm: 11.82
(CH3), 25.04 (CH2), 47.76 (C5), 50.0 (CH2N), 50.74
and 51.38 (OCH3), 103.40 (C4), 105.65 (C2), 111.27
Compounds VI and VII were obtained from 0.14 g
(0.48 mmol) of dichlorocyclopentenone II and 0.26 ml
(1.92 mmol) of dipropylamine.
2-Chloro-3-dipropylamino-4,4-dimethoxy-5-(2-
methylfuran-3-yl)cyclopent-2-en-1-one (VI). Yield
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GIMALOVA et al.
400
(C4′), 113.54 (C3′), 140.11 (C5′), 149.73 (C2′), 159.30
(C3), 190.86 (C1). Found, %: C 58.60; H 6.35;
Cl 10.42; N 4.12. C16H20ClNO4. Calculated, %:
C 58.99; H 6.19; Cl 10.88; N 4.30.
2-Chloro-3-dimethylamino-4,4-dimethoxy-5-
(2-methylfuran-3-yl)cyclopent-2-en-1-one (XII).
Dimethylamine hydrochloride, 0.23 g (2.75 mmol),
was added to a suspension of 0.16 g (2.75 mmol) of
potassium hydroxide in 5 ml of methanol, the mixture
was stirred for 15 min, a solution of 0.2 g (0.68 mmol)
of furylcyclopentenone II in 3 ml of methanol was
added dropwise, and the mixture was stirred at room
temperature until the initial compound disappeared
according to the TLC data (ethyl acetate–petroleum
ether, 1:4). The mixture was then treated as described
above in the synthesis of compound IV, and the resi-
due was subjected to column chromatography on silica
gel using ethyl acetate–petroleum ether (1:5) as eluent
to isolate 0.16 g (76%) of compound XII. White
3-Benzylamino-2-chloro-4,4-dimethoxy-5-(2-
methylfuran-3-yl)cyclopent-2-en-1-one (X) was ob-
tained from 0.1 g (0.34 mmol) of compound II and
0.15 ml (1.36 mmol) of benzylamine. Yield 0.08 g
(64%), yellow–brown powder, mp 130–132°C. IR
spectrum, ν, cm–1: 700, 743, 843, 951, 1273, 1294,
1
1377, 1454, 1533, 1593, 1695, 3048, 3273. H NMR
spectrum, δ, ppm: 2.27 s (3H, CH3), 3.11 s and
3.30 br.s (3H each, OCH3), 3.67 s (1H, 5-H), 4.33 m
and 4.96 m (2H each, NCH2), 6.09 d (1H, 4′-H, J =
1.6 Hz), 7.22–7.44 m (6H, 5′-H, C6H5). 13C NMR
spectrum, δC, ppm: 11.80 (CH3); 44.38 (CH2); 51.26
(C5); 50.76 (OCH3); 103.40 (C4); 110.88 (C3′); 113.02
(C4′); 127.14 (C2); 127.20, 127.66, 128.13, 137.34
(C6H5); 149.93 (C2′); 140.00 (C5′); 138.87 (C3); 176.86
(C1). Found, %: C 62.76; H 5.60; Cl 9.32; N 3.58.
C19H20ClNO4. Calculated, %: C 63.07; H 5.57;
Cl 9.80; N 3.87.
1
needles, mp 90–92°C. H NMR spectrum, δ, ppm:
2.28 s (3H, CH3), 3.03 s and 3.34 s (3H each, OCH3),
3.38 s (6H, NCH3), 3.71 s (1H, 5-H), 6.15 d (1H, 4′-H,
J = 1.9 Hz), 7.25 d (1H, 5′-H, J = 1.9 Hz). 13C NMR
spectrum, δC, ppm: 11.78 (CH3), 41.65 (NCH3), 47.72
(C5), 50.82 and 51.45 (OCH3), 103.81 (C4), 105.99
(C2), 109.41 (C4′), 113.22 (C3′), 140.08 (C5′), 149.73
(C2′), 161.22 (C3), 190.69 (C1). Found, %: C 55.73;
H 6.35; Cl 11.39; N 4.48. C14H18ClNO4. Calculated,
%: C 56.10; H 6.05; Cl 11.83; N 4.67.
2-Chloro-4,4-dimethoxy-5-(2-methylfuran-3-yl)-
3-(2-phenylethylamino)cyclopent-2-en-1-one (XI)
was obtained as a mixture of diastereoisomers from
0.12 g (0.41 mmol) of compound II and 0.2 ml
(1.64 mmol) of α-methylbenzylamine. Yield 0.12 g
(77%), brown powder, mp 196–199°C. IR spectrum, ν,
cm–1: 700, 1072, 1122, 1377, 1458, 1570, 1587, 1629,
3327. Mass spectrum, m/z (Irel, %): 375, 377, 379
(80) [M]+; 340 [M – Cl]+; 270; 268, 266 (30) [M –
PhCHCH3]+; 105 (100) [PhCHCH3]+; 77 [Ph].
1H NMR spectrum, δ, ppm: major isomer: 1.68 m (3H,
CH3), 2.28 s (3H, CH3), 3.13 s and 3.36 s (3H each,
2-Chloro-4,4-dimethoxy-3-methylamino-5-(2-
methylfuran-3-yl)cyclopent-2-en-1-one (XIII) was
obtained in a similar way from 0.1 g (0.34 mmol) of
compound II and 0.095 g (1.21 mmol) of methylamine
hydrochloride. Yield 0.04 g (36%), yellow–brown
crystals, mp 147–149°C. IR spectrum, ν, cm–1: 358,
897, 1130, 1155, 1182, 1271, 1377, 1419, 1458, 1533,
1
1606, 1695, 3294. H NMR spectrum, δ, ppm: 2.28 s
(3H, CH3), 3.03 s and 3.34 s (3H each, OCH3), 3.38 s
(6H, NCH3), 3.71 s (1H, 5-H), 6.15 d (1H, 4′-H, J =
1.9 Hz), 7.25 d (1H, 5′-H, J = 1.9 Hz). 13C NMR spec-
trum, δC, ppm: 11.78 (CH3), 41.65 (NCH3), 47.72 (C5),
50.82 and 51.45 (OCH3), 103.81 (C4), 105.99 (C2),
109.41 (C4′), 113.22 (C3′), 140.08 (C5′), 149.73 (C2′),
161.22 (C3), 190.69 (C1). Mass spectrum, m/z (Irel, %):
286, 288 (70) [M + H]+; 254, 256 (100) [M + H –
CH3OH]+; 220 (20) [M + H – CH3OH – HCl]+.
3
OCH3), 3.64 s (1H, 5-H), 4.79 q.d (1H, CH, J = 6.7,
2J = 13.6 Hz), 5.66 br.s (1H, NH), 6.13 s (1H, 4′-H),
7.16–7.39 m (6H, 5′-H, C6H5); minor isomer: 1.38 d
(3H, CH3, J = 6.8 Hz), 2.27 s (3H, CH3), 3.19 s and
3.31 s (3H each, OCH3), 3.66 s (1H, 5-H), 4.91 m (1H,
CH), 5.66 br.s (1H, NH), 5.98 br.s (1H, 4′-H), 7.16–
7.39 m (6H, 5′-H, C6H5). 13C NMR spectrum, δC, ppm:
major isomer: 11.87 (CH3); 22.61 (CH3); 49.97 (C5);
50.75 (OCH3); 51.18 (CH); 103.0 (C4); 110.97 (C3′);
113.11 (C4′); 125.73, 128.50, 128.92, 142.48 (C6H5);
139.96 (C5′); 144.38 (C2); 149.89 (C2′); 156.83 (C3);
189.06 (C1); minor isomer: 11.77 (CH3); 23.60 (CH3);
49.97 (C5); 51.79 (OCH3); 52.36 (CH); 103.0 (C4);
110.57 (C3′); 113.0 (C4′); 125.88, 126.94, 127.82,
142.83 (C6H5); 139.96 (C5′); 144.38 (C2); 149.76 (C2′);
156.83 (C3); 189.06 (C1).
Compounds XIV and XV were isolated as a mix-
ture at a ratio of ~4:1 from 0.14 g (0.48 mmol) of cy-
clopentenone II and 0.5 ml (1.92 mmol) of diiso-
propylamine. Overall yield 0.1 g (~ 69%).
2-Chloro-3,4,4-trimethoxy-5-(2-methylfuran-3-
yl)cyclopent-2-en-1-one (XIV). 1H NMR spectrum, δ,
ppm: 2.28 s (3H, CH3); 3.27 s, 3.39 s, and 4.45 s (3H
each, OCH3); 3.74 s (1H, 5-H); 6.15 d (1H, 4′-H, J =
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SPECIFICITY OF THE REACTION OF 2,3-DICHLORO-4,4-DIMETHOXY-...
401
1.8 Hz); 7.25 d (1H, 5′-H, J = 1.9 Hz). 13C NMR
REFERENCES
spectrum, δC, ppm: 11.93 (CH3); 51.32 (C5); 51.32,
52.13, and 60.18 (OCH3); 102.24 (C4); 108.91 (C2);
111.43 (C4′); 112.52 (C3′); 140.08 (C5′); 150.22 (C2′);
173.56 (C3); 193.32 (C1).
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Miftakhov, M.S., Izv. Akad. Nauk SSSR, Ser. Khim., 1991,
p. 2405.
2. Rosenkranz, G., Mancera, O., Gatica, J., and Djerassi, C.,
2-Chloro-3-diisopropylamino-4,4-dimethoxy-5-
(2-methylfuran-3-yl)cyclopent-2-en-1-one (XV).
1H NMR spectrum, δ, ppm: 1.34 d (3H, CH3, J =
6.4 Hz), 2.29 s (3H, CH3), 3.16 s and 3.31 s (3H each,
OCH3), 3.43 m and 3.63 m (1H each, CH), 3.67 s (1H,
5-H), 6.34 d (1H, 4′-H, J = 1.8 Hz), 7.22 d (1H, 5′-H,
J = 1.96 Hz).
J. Am. Chem. Soc., 1950, vol. 72, p. 4077.
3. Akbutina, F.A., Yumagulova, S.A., Fatykhov, A.A., and
Miftakhov, M.S., Izv. Ross. Akad. Nauk, Ser. Khim., 2002,
p. 982.
4. Akhmetvaleev, R.R., Akbutina, F.A., Ivanova, N.A., and
Miftakhov, M.S., Izv. Ross. Akad. Nauk, Ser. Khim., 2001,
p. 1417.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 44 No. 3 2008