Reaction of 3,5-disubstituted 4,5-dihydroisoxazoles with hexacarbonylmolybdenum

Article abstract of DOI:10.1023/B:RUJO.0000045194.01881.3c

Depending on the reaction conditions and structure of the 5-substituent, reactions of substituted 4,5-dihydroisoxazoles with hexacarbonylmolybdenum involve cleavage of the heteroring at the N-O bond, its aromatization, or/and 1,3-decyclization.

Full text of DOI:10.1023/B:RUJO.0000045194.01881.3c

Russian Journal of Organic Chemistry, Vol. 40, No. 7, 2004, pp. 1003–1008. Translated from Zhurnal Organicheskoi Khimii, Vol. 40, No. 7, 2004,
pp. 1044–1049.
Original Russian Text Copyright © 2004 by Koroleva, Katok, Lakhvich.
Reaction of 3,5-Disubstituted 4,5-Dihydroisoxazoles
with Hexacarbonylmolybdenum
E. V. Koroleva, Ya. M. Katok, and F. A. Lakhvich
Institute of Bioorganic Chemistry, National Academy of Sciences of Belarus,
ul. Akademika Kuprevicha 5/2, Minsk, 220141 Belarus
e-mail: evk@ iboch.bas-net.by
Received July 31, 2002
Abstract—Depending on the reaction conditions and structure of the 5-substituent, reactions of substituted
4,5-dihydroisoxazoles with hexacarbonylmolybdenum involve cleavage of the heteroring at the N–O bond, its
aromatization, or/and 1,3-decyclization.
The use of isoxazole derivatives as synthetic
precursors of various acyclic compounds [1] has
stimulated extensive studies on the development of
preparative methods for implementation of latent
functionality of the isoxazole ring. In the last decades,
a number of effective procedures have been proposed
for the transformation of isoxazole derivatives into
difunctional acyclic compounds in the presence of
organometallic reagents [2].
organometallic compounds (such as butyllithium,
dimsilsodium, and K-Selectride) was described by us
previously [5]. 1,3-Decyclization in the presence of
bases was also reported for 5-acyl- and 5-nitrodihydro-
isoxazoles [6]. However, in the reactions of 4,5-di-
hydroisoxazoles with polycarbonyl metal complexes,
only the corresponding 1,4-decyclization products
were isolated [7]. The above decomposition of 5-pyr-
idyl-4,5-dihydroisoxazoles may be caused by the effect
of the pyridyl substituent which gives rise to specific
interaction with the reagent. With the goal of studying
in detail the observed transformations we have syn-
thesized a series of 3,5-disubstituted 4,5-dihydroiso-
xazoles Ia–Ie having heterocyclic, aromatic, hetero-
aromatic, and functional groups and examined their
reactions with Mo(CO)6.
Isoxazoles Ia–Ie were prepared by 1,3-dipolar
cycloaddition to 4-vinylpyridine, 1-vinylpyrrolidin-2-
one, and 1-vinylimidazole of nitrile oxides generated
in situ from the corresponding nitro compounds or
oxime chlorides [8]. The reactions of compounds Ia–Ie
with Mo(CO)6 were carried out in methanol or aceto-
nitrile under the conditions typical for ring opening in
4,5-dihydroisoxazole derivatives. After primary treat-
ment of the reaction mixture, the products were
identified and their ratio was determined by IR and 1H
NMR spectroscopy. All products were isolated and
characterized by the mass, IR, and 1H NMR spectra.
While studying the synthesis of prostaglandin
analogs via isoxazole methodology [3], we have
encountered with the problem of choosing a reagent
for selective cleavage of the heteroring in polyfunc-
tional isoxazole derivatives. The most effective was
hexacarbonylmolybdenum Mo(CO)6. It ensured
opening of the isoxazole ring in compounds containing
such groups as HC=CH, C=O, and COOR (i.e., sen-
sitive to reducing agents) to the corresponding
1,3-aminoeneketones in up to 80% yield [4]. The
efficiency of Mo(CO)6 as a reagent for cleavage of
dihydroisoxazole ring was demonstrated using a series
of 5-substituted 4,5-dihydroisoxazoles having alkyl
and aryl substituents on C5. Here, no other products
than 1,3-hydroxy ketones (products of heteroring
opening at the N–O bond) was observed. However,
in the reaction of 5-pyridyl-4,5-dihydroisoxazole (Ia)
with Mo(CO)6, aprat from the target hydroxy ketone
IIa, compounds III–VI were isolated. Their formation
indicates more profound decomposition of the isoxa-
zole ring involving additional cleavage of the C3–C4
(1,3-decyclization) or C4–C5 bond (1,4-decyclization).
Depending on the conditions (solvent, temperature,
reaction time, presence of water), dihydroisoxazoles
Ia–Ie reacted with Mo(CO)6 to afford compounds II–
VII which correspond to three possible modes of
opening of the heteroring, and isoxazole VIII can be
The ability of 5-(4-pyridyl)-4,5-dihydroisoxazoles
to undergo 1,3-decyclization by the action of some
1070-4280/04/4007-1003 © 2004 MAIK “Nauka/Interperiodica”

KOROLEVA et al.
1004
Scheme 1.
R1
R2
R1
R2
1,2-Decomposition
O
OH
O
IIa–IIc
VIId
1,3-Decyclization
1,4-Decyclization
+
R2COMe
R1C
IIIa–IIIc
N
R1
IV
3
4
Mo(CO)6
2N
5
R1
Me
1
O
R2
+
R2CHO
Ia–Ie
O
Va–Vc
VI
R1
R1
H
Aromatization
–HR2
N
NH2
IXe
O
O
VIIIe
R1 = 2-(6-methoxycarbonylhexyl)-3-oxocyclopentyl, R2 = 4-pyridyl (a); R1 = 4-methoxycarbonylbutyl, R2 = 4-pyridyl (b); R1 =
3,4-dimethoxyphenyl, R2 = 4-pyridyl (c); R1 = 2-(6-methoxycarbonylhexyl)-3-oxocyclopentyl, R2 = 1-(2-oxopyrrolidinyl) (d);
R1 = 2-(6-methoxycarbonylhexyl)-3-oxocyclopentyl, R2 = 1-imidazolyl (e).
regarded as an aromatization product (Scheme 1).
According to the H NMR data, the reaction mixtures
water accelerates the process, and dihydroisoxazoles
Ia–Ic in 6 h are completely converted into mixtures
of ketones IIa–IIc (up to 45%) together with 4-acetyl-
pyridine and the corresponding nitrile (10–15%).
1
contained 1,3-hydroxy ketones IIa–IIc, nitriles IIIa–
IIIc, 4-acetylpyridine (IV), as well as methyl ketones
Va–Vc and 4-pyridinecarbaldehyde (VI). Nitriles
IIIa–IIIc were also identified by the presence in the
IR spectrum of a characteristic absorption band at
2225–2260 cm–1, belonging to stretching vibrations
of the C≡N bond. 4-Acetylpyridine showed in the
1H NMR spectrum a singlet at δ 2.65 ppm from the
acetyl methyl protons and two doublets at δ 7.78 and
8.82 ppm (J = 5.0 Hz) from the aromatic protons, and
a band at 1690 cm–1 was present in the IR spectrum
The absence of aldehyde VI in the reaction mixture
in 3 h after the reaction started suggests that pyridine-
carbaldehyde and methyl ketone V are products of
retro-aldol decomposition of initially formed hydroxy
ketone II rather than of synchronous 1,4-decyclization
of dihydroisoxazole. In fact, considering dihydroiso-
xazoles to be a latent form of β-hydroxy ketones, and
the formation of dihydroisoxazoles and their decom-
position to hydroxy ketones, an equivalent of aldol
condensation, the 1,4-decyclization may be regarded as
retro-aldol decomposition. Obviously, the decomposi-
tion of hydroxy ketone occurs with participation of
Mo(CO)6. As a rule, the complete conversion of di-
hydroisoxazole is attained in 2 days with formation of
compounds III–VI. When the reaction was carried out
in anhydrous methanol, only the unchanged initial
compounds were isolated, while the main reaction
pathway in aqueous methanol was 1,3-decyclization.
1
due to the conjugated carbonyl group. The H NMR
spectrum of 4-pyridinecarbaldehyde (VI) contained
a signal at δ 10.28 ppm due to the aldehyde proton, and
methyl ketones Va–Vc gave rise to a three-proton
singlet from the methyl protons at δ 2.15–2.18 ppm
(Va, Vb) or 2.78 ppm (Vc).
The reaction with Mo(CO)6 in anhydrous aceto-
nitrile was characterized by low conversion of the
initial dihydroisoxazole. In 3 h, the overall yield of
the corresponding 1,3-hydroxy ketone, nitrile, and
4-acetylpyridine (ratio 8:1:1) from compounds Ia–Ic
was no less than 25%. When the reaction was
prolonged to more than 2 days, the products were
4-pyridinecarbaldehyde, ketones Va–Vc, and traces of
hydroxy ketones IIa–IIc. The presence of traces of
The structure of the 5-substituent is an important
factor determining the mode of ring opening in di-
hydroisoxazoles by the action of Mo(CO)6. Presum-
ably, the presence of a pyridyl group in position 5
favors 1,3-decyclization; however, this substituent
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 40 No. 7 2004

REACTION OF 3,5-DISUBSTITUTED 4,5-DIHYDROISOXAZOLES
1005
does not affect the ability of hydroxy ketone thus
formed to undergo retro-aldol reaction. For example,
hydroxy ketones IIa and IIb are more stable than IIc,
and the amount of 1,3-decyclization products in the
reaction mixture attains 15%. If both substituents in
4,5-dihydroisoxazole are aromatic (as in compound
Ic), 1,3-decyclization competes with 1,2-decomposi-
tion. After 3 h, the reaction mixture contains com-
pounds II, III, and IV at a ratio of 1:2:2; after 2 days,
no hydroxy ketone II was present, but pyridine-
carbaldehyde (δ, ppm: 10.28, 7.50, 8.75 ppm) and
methyl 3,4-dimethoxyphenyl ketone (Vc; δ 2.75 ppm,
MeCO) were identified instead.
spectra were measured on a UR-20 instrument from
samples prepared as thin films. The mass spectra
(70 eV) were run on a Varian MAT-311 mass spec-
trometer. The progress of reactions and the purity of
products were monitored by TLC on Silufol UV-254
(Serva) and Kieselgel 60 F254 plates (Merck) using
hexane–ether (65:35) or chloroform–methanol (85:15)
as eluent; spots were visualized by UV irradiation or
by treatment with iodine or a mixture of EtOH (90%),
H2SO4 (5%), and 4-methoxybenzaldehyde (5%). Silica
gel 40/100 µm (Czechia) was used for column
chromatography. Preparative thin-layer chromatog-
raphy was performed on Kieselgel L 5/40 µm applied
to glass plates using a solution of 5% of methanol in
chloroform as eluent.
5-(2-Oxo-1-pyrrolidinyl)-4,5-dihydroisoxazole (Id)
did not react with Mo(CO)6 in anhydrous acetonitrile.
In the presence of water, the major product was enone
VIId which was formed as a result of dehydration of
hydroxy ketone IId. Enone VIId was isolated in
a preparative yield. Obviously, the formation of VIId
is favored by conjugation between the heteroatom and
carbonyl group in the pyrrolidine ring.
Initial 4,5-dihydroisoxazoles Ia–Ie were synthe-
sized by the procedures described in [8, 11] and were
isolated as oily substances.
3-[2-(6-Methoxycarbonylhexyl)-3-oxocyclo-
pentyl]-5-(4-pyridyl)-4,5-dihydroisoxazole (Ia).
Yield 85%. IR spectrum, ν, cm–1: 1600, 1610, 1740.
1H NMR spectrum, δ, ppm: 1.20–2.00 m (13H, CH2),
2.26 m (4H, CH2CO2Me, CH2CO), 2.92 d.d (1H, 4-H,
isoxazole, J = 18.0, 7.0 Hz), 2.98 m (1H, CHC=N–O),
3.50 d.d (1H, 4-H, isoxazole, J = 18.0, 10.0 Hz),
3.68 s (3H, OCH3), 5.63 d.d (1H, J = 10.0, 7.0 Hz,
5-H, isoxazole), 7.24 m and 8.60 m (4H, pyridine).
Mass spectrum, m/z: 372 [M]+. Found, %: C 67.84;
H 7.49; N 7.56. C21H28N2O4. Calculated, %: C 67.72;
H 7.58; N 7.52.
The reaction of 5-imidazolylisoxazole (Ie) with
Mo(CO)6 leads to formation of enaminoaldehyde IXe
in 40% yield. Obviously, compound IXe is the product
of reductive cleavage of intermediate isoxazole VIIIe
which is formed in turn by aromatization of the
dihydroisoxazole ring via elimination of imidazole
molecule. The aromatization is likely to be favored by
the presence of a readily departing group at C5. This
is also confirmed by the formation of a considerable
amount of isoxazole VIIIe as by-product in the
synthesis of 5-imidazolyl-4,5-dihydroisoxazole and by
the failure to obtain 3-veratryl-5-(1-imidazolyl)-4,5-di-
hydroisoxazole. In the latter case, cycloaddition of
3,4-dimethoxybenzonitrile oxide to 1-vinylimidazole
afforded 3-veratrylisoxazole [9].
3-(4-Methoxycarbonylbutyl)-5-(4-pyridyl)-4,5-
dihydroisoxazole (Ib). Yield 80%. IR spectrum, ν,
1
cm–1: 1520, 1580, 1600, 1730. H NMR spectrum, δ,
ppm: 1.68 m (4H, CH2CH2CH2CH2CO2Me), 2.38 m
(4H, CH2(CH2)2CH2CO2Me), 2.84 d.d (1H, 4-H,
isoxazole, J = 17.0, 7.0 Hz), 3.46 d.d (1H, 4-H,
isoxazole, J = 17.0, 11.0 Hz), 3.66 s (3H, OCH3),
5.66 d.d (1H, 5-H, isoxazole, J = 11.0, 7.0 Hz), 7.26 d
and 8.62 d (4H, J = 4.5 Hz, pyridine). Mass spectrum,
m/z: 274 [M]+. Found, %: C 65.58; H 6.67; N 10.23.
C15H18N2O3. Calculated, %: C 65.68; H 6.61; N 10.21.
It should be noted that 1,3-decyclization of
5-(4-pyridyl)-4,5-dihydroisoxazoles by the action of
Mo(CO)6 has never been observed for analogous
5-phenyl-4,5-dihydroisoxazoles. However, Nitta and
Kobayashi [10] described 1,4-decyclization products
formed by the action of Mo(CO)6 on 5-phenyl-sub-
stituted 4,5-dihydroisoxazoles in anhydrous aceto-
nitrile [10].
3-(3,4-Dimethoxyphenyl)-5-(4-pyridyl)-4,5-di-
hydroisoxazole (Ic). Yield 80%. IR spectrum, ν, cm–1:
1
1025, 1520, 1605, 1650, 1720. H NMR spectrum, δ,
ppm: 3.38 d.d (1H, 5-H, isoxazole, J = 7.5, 17.0 Hz),
3.86 d.d (1H, 4-H, isoxazole, J = 11.0, 17.0 Hz), 3.96 s
and 3.87 s (6H, OCH3), 5.74 d.d (1H, 5-H, isoxazole,
J = 7.5, 11.0 Hz), 6.30 d.d and 7.72 d (3H, C6H3, J =
8.5, 2.0, 8.5 Hz), 7.34 d and 8.60 d (4H, pyridine, J =
5.0 Hz). Mass spectrum, m/z: 284 [M]+. Found, %:
EXPERIMENTAL
1
The H NMR spectra were recorded on a Bruker
AC-200 spectrometer (200 MHz) from solutions in
CDCl3 containing TMS as internal reference. The IR
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 40 No. 7 2004

KOROLEVA et al.
1006
C 67.68; H 5.62; N 9.91. C16H16N2O3. Calculated, %:
C 67.59; H 5.67; N 9.85.
8.0 Hz), 2.58 m (1H, CHC=O, cyclopentyl), 2.83 d.d
(1H, COCHCHOH, J = 18.0, 3.0 Hz,], 2.92 m (1H,
CHC=O, cyclopentyl), 3.03 d.d (1H, CHCHOH, J =
18.0, 8.0 Hz), 3.68 s (3H, OCH3), 5.28 d.d (1H,
CHOH, J = 8.0, 3.0 Hz), 7.23 m and 8.60 m (4H,
pyridyl). Mass spectrum, m/z: 375 [M]+. Found, %:
C 67.04; H 7.80; N 3.78. C21H29NO5. Calculated, %:
C 67.18; H 7.78; N 3.73.
3-[2-(6-Methoxycarbonylhexyl)-3-oxo-3-cyclo-
pentyl]-5-(2-oxo-1-pyrrolidinyl)-4,5-dihydroisoxa-
zole (Id). Yield 80%. IR spectrum, ν, cm–1: 1610,
1
1640, 1710, 1750. H NMR spectrum, δ, ppm: 1.40–
2.00 m (14H, CH2), 2.12 m (1H, CHC=O, cyclo-
pentyl), 2.38 t (4H, CH2CO2Me, CH2CO, J = 8.0 Hz),
2.5 t (2H, CH2CO, pyrrolidine, J = 8.0 Hz), 2.82 d.d
(1H, 4-H, isoxazole, J = 3.0, 17.5 Hz), 2.98 m (1H,
CHC=N–O, cyclopentyl, J = 11.0 Hz), 3.18 m and
3.36 m (1H, 4-H, isoxazole), 3.66 s (3H, OCH3),
6.56 d.d (1H, 5-H, isoxazole, J = 3.0, 10.0 Hz), 3.34 m
(2H, CH2N, pyrrolidine). Mass spectrum, m/z: 378
[M]+. Found, %: C 63.56; H 7.92; N 7.33. C20H30N2O5.
Calculated, %: C 63.47; H 7.99; N 7.40.
3-Hydroxy-1-(4-methoxycarbonylbutyl)-3-(4-
pyridyl)-1-propanone (IIb). Yield 50%. IR spectrum,
ν, cm–1: 1600, 1710, 1740, 3400. 1H NMR spectrum, δ,
ppm: 1.58 m (4H, CH2CH2CH2CH2CO2Me); 2.28–
2.60 m (4H, CH2(CH2)2CH2CO2Me); 2.80 d.d (2H,
COCH2CHOH, J = 5.0 Hz); 5.70 m (1H, CHOH);
7.39 d, 7.68 d, 8.56 d, and 8.65 d (4H, pyridyl, J =
5.0 Hz). Mass spectrum, m/z: 265 [M]+. Found, %:
C 63.30; H 7.28; N 5.38. C14H19NO4. Calculated, %:
C 63.38; H 7.22; N 5.28.
5-(1-Imidazolyl)-3-[2-(6-methoxycarbonylhexyl)-
3-oxocyclopentyl]-4,5-dihydroisoxazole (Ie). Yield
55%. IR spectrum, ν, cm–1: 1605, 1740. 1H NMR spec-
trum, δ, ppm: 1.20–2.00 m (13H, CH2,); 2.26 m
(4H, CH2CO2Me, CH2CO); 3.05 q (1H, CHC=N–O,
cyclopentyl); 3.15 and 3.24 d.t (1H, 4-H, isoxazole, J =
18.0, 3.5 Hz,); 3.54 q (1H, 4-H, isoxazole, J = 18.0,
9.0 Hz): 3.66 s (3H, OCH3), 6.44 d.d (1H, 5-H, J = 9.0,
3.5 Hz; 6.90 s, 7.12 s, 7.68 s (3H, imidazole). Mass
spectrum, m/z: 361 [M]+. Found, %: C 62.99; H 7.59;
N 11.70. C19H27N3O4. Calculated, %: C 63.14; H 7.53;
N 11.63.
1-(3,4-Dimethoxyphenyl)-3-hydroxy-3-(4-pyri-
dyl)-1-propanone (IIc). Yield 54%. IR spectrum, ν,
1
cm–1: 1025, 1610, 1670, 3450. H NMR spectrum, δ,
ppm: 3.26 d.d (1H, CHCHOH, J = 9.0, 16.0 Hz),
3.44 d.d (1H, CHCHOH) 3.89 s and 3.91 s (6H,
OCH3), 5.28 d.d (1H, CHOH, J = 9.0, 3.0 Hz), 6.44 d
(1H, 3-H in C6H3, J = 1.5 Hz), 6.56 d.d (1H, 5-H in
C6H3, J = 1.5 Hz), 7.36 d (2H, pyridine, J = 5.0 Hz),
7.88 d (1H, 6-H in C6H3, J = 8.5 Hz), 8.56 br.s (2H,
pyridine). Mass spectrum, m/z: 287 [M]+. Found, %:
C 67.00; H 5.95; N 4.90. C16H17NO4. Calculated, %:
C 66.89; H 5.96; N 4.88.
Reaction of 4,5-dihydroisoxazoles with hexa-
carbonylmolybdenum (general procedure). Water,
1 mmol, and hexacarbonylmolybdenum, 0.5–1 mmol,
were added to a solution of 1 mmol of isoxazole I in
20 ml of acetonitrile or methanol, and the mixture was
heated for 8–24 h under reflux, the progress of the
reaction being monitored by TLC. The mixture was
diluted with hexane or hexane–benzene (1:1) and
filtered through celite 545, the filtrate was evaporated,
and the residue was subjected to column chromatog-
raphy on silica gel using diethyl ether as eluent. The
products were isolated by column chromatography or
preparative thin-layer chromatography with an overall
yield of 55–70%. The isolated compounds were color-
less oily substances.
7-(2-Cyano-5-oxocyclopentyl)heptanoic acid
(IIIa). Yield 60%. IR spectrum, ν, cm–1: 1740, 2245,
1
3500. H NMR spectrum, δ, ppm: 1.2–2.00 m (13H,
CH2, CH), 2.35 t (4H, CH2COOH, CH2CO, J =
8.0 Hz), 2.65 d.d.d (1H, CHCN, J = 11.7, 10.0,
6.5 Hz), 5.0 br.s (COOH). Mass spectrum, m/z: 237
[M]+. Found, %: C 65.94; H 7.95; N 5.85. C13H19NO3.
Calculated, %: C 65.80; H 8.07; N 5.90.
5-Cyanopentanoic acid (IIIb). Yield 60%. IR
spectrum, ν, cm–1: 1260, 1690, 1710, 2260, 3400.
1H NMR spectrum, δ, ppm: 1.20–1.70 m (4H, CH2),
2.40 m (4H, CH2CH, CH2COOH). Mass spectrum,
m/z: 127 [M]+. Found, %: C 56.31; H 7.24; N 11.06.
C6H9NO2. Calculated, %: C 56.68; H 7.13; N 11.02.
3-Hydroxy-1-[2-(6-methoxycarbonylhexyl)-3-
oxocyclopentyl]-3-(4-pyridyl)-1-propanone (IIa).
Yield 56%. IR spectrum, ν, cm–1: 600, 1710, 1735,
3,4-Dimethoxybenzonitrile (IIIc). Yield 60%. IR
spectrum, ν, cm–1: 810, 1030, 1580, 1610, 2220.
1H NMR spectrum, δ, ppm: 3.85 s and 3.90 s (6H,
OMe), 6.46 d (1H, 2-H, J = 1.7 Hz), 6.50 d.d (1H, 6-H,
1
3380. H NMR spectrum, δ, ppm: 1.20–2.00 m (12H,
CH2, CH), 2.30 t (4H, CH2CO2Me, CH2CO, J =
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REACTION OF 3,5-DISUBSTITUTED 4,5-DIHYDROISOXAZOLES
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J = 10.0, 1.7 Hz), 7.46 d (1H, 5-H, J = 10.0 Hz). Mass
spectrum, m/z: 163 [M]+. Found, %: C 66.33; H 5.58;
N 8.61. C9H9NO2. Calculated, %: C 66.25; H 5.56;
N 8.58.
3-[2-(6-Methoxycarbonylhexyl)-3-oxocyclo-
pentyl]isoxazole (VIII). Yield 63%. IR spectrum, ν,
1
cm–1: 1560, 1595, 1730, 3440. H NMR spectrum, δ,
ppm: 1.30–2.10 m (13H, CH2, CH), 2.28 t (4H,
CH2CO2Me, CH2CO, J = 8.0 Hz), 3.18 m (1H, 3-CH),
3.65 s (3H, OCH3), 6.10 d (1H, 4-H, J = 1.0 Hz),
8.35 d (1H, 5-H, J = 1.0 Hz). Mass spectrum, m/z: 293
[M]+. Found, %: C 65.38; H 7.79; N 4.80. C16H23NO4.
Calculated, %: C 65.51; H 7.90; N 4.77.
4-Acetylpyridine (IV). IR spectrum, ν, cm–1: 1600,
1
1690, 1740. H NMR spectrum, δ, ppm: 2.65 s (3H,
CH3CO), 7.78 d and 8.82 d (4H, pyridine, J = 5.0 Hz).
Mass spectrum, m/z: 121 [M]+. Found, %: C 69.37;
H 5.89; N 11.58. C7H7NO. Calculated, %: C 69.41;
H 5.82; N 11.56.
3-Amino-3-[2-(6-methoxycarbonylhexyl)-3-oxo-
cyclopentyl]-2-propenal (IX). Yield 40%. IR spec-
trum, ν, cm–1: 1540, 1625, 1740, 3200, 3440. 1H NMR
spectrum, δ, ppm: 1.30–2.00 m (13H, CH2, CH), 2.30 t
(4H, CH2CO2CH3, CH2CO, J = 8.0 Hz), 2.98 m (1H,
CHCNH2), 3.65 s (3H, OCH3), 5.12 br.s (1H,
NH2C=CH, J = 2.5 Hz), 9.18 d (1H, CHO, J = 2.5 Hz),
5.4, 10.0 br.s (2H, NH2). Mass spectrum, m/z: 295
[M]+. Found, %: C 65.21; H 8.63; N 4.65. C16H25NO4.
Calculated, %: C 65.06; H 8.53; N 4.74.
Methyl 7-(2-acetyl-5-oxocyclopentyl)heptanoate
(Va). Yield 20%. IR spectrum, ν, cm–1: 1500, 1715,
1
1740. H NMR spectrum, δ, ppm: 1.64–1.80 m (13H,
CH2, CH), 2.18 s (3H, CH3CO), 2.35 t (4H,
CH2COOMe, CH2CO, J = 8.0 Hz), 2.9 m (1H, CHCO,
cyclopentyl), 3.68 s (3H, OCH3). Mass spectrum, m/z:
268 [M]+. Found, %: C 67.09; H 8.91. C15H24O4. Cal-
culated, %: C 67.16; H 8.95.
Methyl 5-oxohexanoate (Vb). IR spectrum, ν,
1
cm–1: 1735–1750. H NMR spectrum, δ, ppm: 1.68–
This study was performed under financial support
by the Belarussian Republican Foundation for Basic
Research (project no. Kh99-021).
1.72 m (4H, CH2), 2.15 s (3H, CH3CO), 2.35 m (4H,
CH2CO), 3.68 s (3H, OCH3). Mass spectrum, m/z: 158
[M]+. Found, %: C 60.78; H 9.01. C8H14O3. Calculated,
%: C 60.74; H 8.92.
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1
trum, ν, cm–1: 830, 1035, 1570, 1605. H NMR
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1
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RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 40 No. 7 2004