4
,5-DIHYDROISOXAZOLES FROM ARYLCYCLOPROPANES: II.
569
tively stable; therefore, the contribution of the elimina-
tion process to stabilization of primary carbocation is
likely to increase (path b) together with nucleophilic
attack by the oxygen atom of the nitroso group. The
subsequent isomerization of unsaturated nitroso com-
pound to the corresponding oxime, followed by hy-
drolysis during the isolation procedure, leads to the
formation of aldehyde IIIb.
rial partially dissolved, and the solution turned colored.
When the reaction was complete (TLC), the mixture
was neutralized with a solution of sodium carbonate
and washed with water. The aqueous phase was sepa-
rated and extracted with methylene chloride (3×
10 ml), and the extracts were combined with the organ-
ic phase, dried over sodium sulfate, and evaporated.
The residue was pure crystalline compound IIa–IIn.
If necessary, the product can be purified by recrystal-
lization or chromatography.
3
-(4-Methoxyphenyl)prop-2-enenitrile (IVb) can be
formed as a result of dehydration of unsaturated
oxime. This process is facilitated by anti arrangement
of the hydrogen atom and OH group in the oxime [6].
Prolonged reaction time favors formation of nitrile
IVb, while the fraction of aldehyde IIIb among the
products decreases (Table 5); these data confirm the
possibility for the transformation of intermediate
oximes into nitrile IVb. In addition, 4-methoxycin-
namaldehyde (IIIb) and 4-methoxycinnamonitrile
In the reaction of 0.105 g (0.7 mmol) of compound
Ib with 0.16 g (0.7 mmol) of NOCl·2SO at 0°C (2 h)
3
we isolated by chromatography (silica gel, ethyl ace-
tate–petroleum ether, 1:3) 0.05 g (41%) of trans-3-(4-
methoxyphenyl)prop-2-enenitrile (IVb), 0.01 g (11%)
of trans-3-(4-methoxyphenyl)prop-2-enal (IIIb), and
0.05 g (42%) of 5-(4-methoxyphenyl)-4,5-dihydroiso-
xazole (IIb).
(
IVb) can be formed via dehydration of dihydroisoxa-
–1
Compound IIb. R 0.21. IR spectrum: ν 1620 cm
f
zole IIb during the reaction; this pathway may also be
responsible for the anomalously high yields of com-
pounds IIIb and IVb.
Thus the results of the present study showed that
arylcyclopropanes readily react with the complex
(
C=N).
–1
Compound IIIb. R 0.66. IR spectrum ν, cm : 1675
f
(
C=O), 1610, 1360, 1135, 830, 810.
–1
Compound IVb. R 0.82. IR spectrum, ν, cm :
f
2225 (CN), 1610, 1580, 1260, 1180, 1030, 810, 750.
NOCl·2SO to give the corresponding 5-aryl-4,5-di-
3
Found, %: C 75.58; H 5.80; N 8.56. C H NO. Cal-
hydroisoxazoles. The use of NOCl·2SO as highly ef-
10
9
3
fective nitrosating agent allows considerable extension
of the substrate series. In most cases, 5-aryl-4,5-dihy-
droisoxazoles are formed in quantitative yields, and
no additional purification of the product is necessary,
which makes the proposed procedure especially advan-
tageous from the preparative viewpoint.
culated, %: C 75.47; H 5.66; N 8.81;
In the reaction of 0.35 g (1.4 mmol) of 4-bromo-2-
nitrophenylcyclopropane (Im) with 0.25 g (1.1 mmol)
of NOCl·2SO we isolated by chromatography (silica
3
gel, ethyl acetate–petroleum ether, 1:5) 0.05 g of
an unidentified substance (R 0.72), 0.05 g (14%) of
f
trans-3-(4-bromo-2-nitrophenyl)prop-2-enal (IIIm),
and 0.12 g (70%) of 5-(4-bromo-2-nitrophenyl)-4,5-di-
hydroisoxazole (IIm).
EXPERIMENTAL
The NMR spectra were recorded on Varian XR-400
and Bruker Avance-400 spectrometers (400 MHz for
Compound IIm. R 0.22, mp 85–87°C (from ethyl
f
–1
1
13
acetate–petroleum ether). IR spectrum, ν, cm : 3110,
H and 100 MHz for C) using CDCl as solvent and
3
2
1
1
1
930, 2860, 1600, 1540 (NO ), 1470, 1430, 1350 (NO ),
tetramethylsilane as internal reference. The IR spectra
were measured on a UR-20 spectrometer from samples
prepared as thin films. The mass spectra were obtained
on a Finnigan MAT SSQ-7000 GC–MS system [elec-
tron impact, 70 eV; OV-1 quartz capillary column,
2
2
1
3
280, 845. C NMR spectrum, δ , ppm: 44.42, 75.99,
C
i
21.88 (C–Br), 127.95, 129.09, 136.76, 137.18 (C ),
45.73 (CNO , HC=N). Mass spectrum, m/z (I , %):
2
rel
+
+
[
(
M] 272/270 (1), 255/253 (8), 242/240 [M – NO]
23), 225 (25), 212 (27), 184/182 (37), 172/170 (27),
2
5 m; oven temperature programming from 70 (2 min)
to 280°C (10 min) at a rate of 20 deg/min]. The melt-
161 (100), 131 (11), 115 (29), 90 (39), 75 (70), 63 (31).
ing points were determined in open capillaries.
Compound IIIm. R 0.52, mp 118–119°C (from
f
–1
Reaction of arylcyclopropanes with NOCl·2SO3
general procedure). A solution of 1 mmol of aryl-
ethyl acetate–petroleum ether). IR spectrum, ν, cm :
2930, 2865, 1690 (C=O), 1600, 1540 (NO ), 1460,
1350 (NO ), 1280, 770. C NMR spectrum, δ , ppm:
(
2
1
3
cyclopropane Ia–In in 2 ml of methylene chloride was
added at 0°C to a suspension of 1 mmol of NOCl·
2
C
i
124.66 (C–Br), 128.21, 128.73 (C ), 130.13, 132.83,
136.84, 145.81 (ArC=, CNO ), 192.75. Mass spec-
2
SO in 10 ml of methylene chloride. The solid mate-
2
3
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 43 No. 4 2007