Factors in molecular structure to activate nitro compounds for organic transformations

Article abstract of DOI:10.1016/S0040-4020(00)00008-9

Activation of nitro compounds was accomplished by introduction of angle strain, γ,δ-unsaturation, or a γ-silyl group. Results from a systematic study indicate that coexistence of two or more of these factors in aliphatic nitro compounds allowed transformations to take place under ambient conditions upon catalysis with AlCl₃, TiCl₄, BF₃ · OEt₂, or SnCl₄. Consequently, structurally modified nitro starting materials led to products in the class of nitroalkyl cyclopentadiene, cyclohydroxamic ester, and chlorohydroxamic acid. (C) 2000 Elsevier Science Ltd.

Full text of DOI:10.1016/S0040-4020(00)00008-9

TETRAHEDRON
Pergamon
Tetrahedron 56 (2000) 1631–1636
Factors in Molecular Structure to Activate Nitro Compounds for
Organic Transformations
b
b
Den-Nan Horng,a, Keh-Loong Chen and Jih Ru Hwu
*
aDepartment of Physics and Chemistry, Chinese Military Academy, P.O. Box 90602-6, Feng-shan, Taiwan, ROC
bDepartment of Chemistry, National Tsing Hua University, Hsinchu, Taiwan 30043, ROC
Received 25 October 1999; accepted 20 December 1999
Abstract—Activation of nitro compounds was accomplished by introduction of angle strain, g,d-unsaturation, or a g-silyl group. Results
from a systematic study indicate that coexistence of two or more of these factors in aliphatic nitro compounds allowed transformations to take
place under ambient conditions upon catalysis with AlCl3, TiCl4, BF3·OEt2, or SnCl4. Consequently, structurally modified nitro starting
materials led to products in the class of nitroalkyl cyclopentadiene, cyclohydroxamic ester, and chlorohydroxamic acid. ᭧ 2000 Elsevier
Science Ltd. All rights reserved.
Introduction
involving organosilanes as the substrates.8 As a conse-
quence, we found some transformations occurring to these
silicon-containing nitro compounds based on the strategy
shown in Scheme 2. The intriguing conversion of activated
nitro compound 12 to hydroxamic acid derivatives 13 and
14, as shown in Scheme 6, is also unprecedented.
Lewis acids can coordinate with nitro compounds to form
complexes (see Scheme 1).1 These nitro compounds can be
recovered after the Lewis acid is removed. On the other
hand, introduction of certain moieties (such as –OH,
CyO, –SR, etc.) to organic nitro compounds may allow
functional group transformations to take place.2–6 We
decided to search for structural factors that can activate
aliphatic nitro compounds under acidic conditions. After
the structure is modified, the nitro compounds would undergo
transformations smoothly upon Lewis acid catalysis.
Results and Discussion
To explore a way to increase the reactivity of nitro com-
pounds, we introduced different moieties onto the skeleton
Scheme 1.
Reactivity of the commonly used Lewis acids follows the
order AlCl3ϾTiCl4ϾBF3·OEt2ϾSnCl4.7 We applied these
acids to structurally ‘activated’ nitro compounds and
intended to realize the consequent transformations. Herein,
we report our findings on three structural factors that can
enhance the reactivity of aliphatic nitro compounds. They
include buildup of angle strain, existence of g,d-unsatu-
ration, and placement of a g-silyl group.
of nitro compounds. First, we found that nitro compound 19
bearing a b-phenyl group remained intact upon treatment
Introduction of a silyl group into aliphatic nitro compounds
is of particular significance. Its attachment to the hydro-
carbon skeleton often does not alter polarity of organic
compounds; yet silicon may exert an electronic effect
on ionic and radical intermediates generated in reactions
Keywords: nitro compounds; fragmentation reaction; Lewis acids.
Scheme 2.
* Corresponding author. E-mail: horng@ms31.url.com.tw
0040–4020/00/$ - see front matter ᭧ 2000 Elsevier Science Ltd. All rights reserved.
PII: S0040-4020(00)00008-9

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D.-N. Horng et al. / Tetrahedron 56 (2000) 1631–1636
Table 1. Reaction of nitro compounds with a Lewis acid in dichloromethane
Entry
Nitro compound
Lewis acid
Temperature (ЊC)
Reaction time
Result (yield)
1
2
3
4
5
6
7
8
1
2
3
3
3
3
4
5
6
6
6
8
8
9
9
AlCl3
AlCl3
AlCl3
TiCl4
BF3·OEt2
SnCl4
AlCl3
AlCl3
AlCl3
TiCl4
SnCl4
AlCl3
SnCl4
AlCl3
SnCl4
AlCl3
SnCl4
AlCl3
TiCl4
0–25
0–25
25
25
25
25
25
25
25
25
25
0
25
0
25
0
25
25
25
25
25
72 h
2.0 h
72 h
72 h
72 h
72 h
12 h
72 h
12 h
10 min
72 h
5.0 min
72 h
5.0 min
72 h
5.0 min
12 h
12 h
12 h
12 h
12 h
Intact
Styrene (85%)
Intact
Intact
Intact
Intact
Fragmentationa
Intact
9
7 (23%)
7 (42%)
Epimerization (23%)
10 (99%)
Epimerization (18%)
10 (98%)
Epimerization (17%)
13 (48%)ϩ14 (23%)
13 (78%)
16 (72%)ϩ(Et3Si)2O (94%)
16 (66%)ϩ(Et3Si)2O (79%)
16 (58%)ϩ(Et3Si)2O (77%)
16 (67%)ϩ(Et3Si)2O (86%)
10
11
12
13
14
15
16
17
18
19
20
21
12
12
15
15
15
15
BF3·OEt2
SnCl4
a An inseparable mixture was obtained.
with AlCl3 in dichloromethane at 0–25ЊC for 72 h (see entry
1 in Table 1). These results indicate that attachment of a
phenyl group at the b position does not significantly
increase the reactivity of nitro compounds.
Second, we added a trimethylsilyl group at the g position
and a phenyl group at the b position as shown in compound
2. Under the same reaction conditions, complete fragmen-
tation occurred to 2 to give styrene in 85% yield within 2.0 h
(see entry 2 in Table 1). Similarly, g-silyl nitronorbornane 4
was decomposed to give an inseparable mixture upon treat-
ment with AlCl3 (entry 7), yet non-silylated nitronorbornane
5
10 was found intact (entry 8). Thus, introduction of a g-silyl
group into nitro compounds could increase their reactivity
towards a Lewis acid although it may not be the only factor
responsible for a fragmentation to take place.
Third, we found that cis- and trans-nitrocyclohexanes 3
were intact towards all four Lewis acids (see entries 3–6
in Table 1). These g-silyl nitro compounds do not possess a
Scheme 3.

D.-N. Horng et al. / Tetrahedron 56 (2000) 1631–1636
1633
Scheme 4.
Scheme 5.
b-phenyl group (cf. 2), nor angle strain (cf. 4). In com-
parison with our observations on 2 and 4, we believe that
these two structural factors also contribute to the activity of
aliphatic nitro compounds under acidic conditions.
silyl nitronorbornenes readily gave the ring-opening product
10 in excellent yields by loss of a silyl group upon treatment
with AlCl3 at 0ЊC (entries 12 and 14). The efficiency was
independent upon the bulk of the silyl group therein inclu-
ding the Me3Si group in 8 and the Et3Si group in 9. These
reactions may go through a concerted pathway.
Ranganathan et al.11 reported that the sodium salt of 612 goes
through an abnormal Nef reaction to give cyclic hydroxamic
ester 7 (Scheme 3). We found that the same conversion can
be accomplished in 42% yield by using TiCl4 (see entry 10
in Table 1). Compound 6, however, was decomposed to give
a mixture containing 7 (23%) upon exposure to a stronger
Lewis acid AlCl3 (entry 9). It was, however, epimerized at
the a carbon by a weaker Lewis acid SnCl4 (entry 11).
Epimerization also occurred to the corresponding silylated
dihydronorbornene nitro compounds 8 and 9 upon treatment
with a weaker Lewis acid SnCl4 (entries 13 and 15).
1
The H NMR spectrum of the product 10 showed four
vinylic protons. Therefore we assigned the nitroalkyl sub-
stituent therein attached to the sp3 carbon of a cyclopen-
tadiene nucleus. During the fragmentation process, the
two C–C double bonds did not scramble in the five-
membered nucleus. We believe that it is due to the mild
conditions applied to the reaction.
Fujita et al.14 reported a method for ring opening of g-silyl
cyclopropyl ketones by Lewis acids (see Scheme 5). We
introduced a b-phenyl or a g-silyl group into a nitrocyclo-
propane and then explored their reactivity towards Lewis
acids (see Scheme 6). Upon treatment with AlCl3 at 0ЊC,
phenylcyclopropane 1215 gave a mixture of cyclohydrox-
amic ester 1316 (48% yield) and chlorohydroxamic acid
1417 (23% yield, entry 16 in Table 1). Replacement of
AlCl3 with a weaker Lewis acid SnCl4 afforded an appealing
yield of 13 (78%, entry 17). Both of hydroxamic derivatives
13 and 14 came from Lewis acid induced opening of a
nitrocyclopropyl ring. Participation of the nitro group in
an intramolecular cyclization led 12 to 13. The unexpected
by-product 14 was generated from an intermolecular
chloride ion transfer from AlCl3 to the ring-opening
Silicon can exert a- and b-effects, which allow reactions to
take place in a promoted or directed manner.8,13 Reactions
involving the g-effect of silicon, however, are limited;
silicon-promoted Nef reaction shown in Scheme
4
represents a prominent example.10 The conversion of g-silyl
bicyclic nitro compound 4 to the corresponding ketone 11
can be accomplished in 91% yield by use of KH in THF
followed by 3.5% of aqueous HCl. In comparison with
compounds 4 and 6, nitro compounds 8 and 9 possess all
of the three structural features: a g-silyl group, angle strain,
and a vinyl moiety attached at the b position. The silyl
groups anti to the nitro groups in 8 and 9 offered an ideal
alignment for a stereoelectronic effect. We found that these
Scheme 6.

1634
D.-N. Horng et al. / Tetrahedron 56 (2000) 1631–1636
intermediate. In its mass spectrum, two sets of peaks at 183/
181 and 127/125 exhibited a ratio of 1:3. These results
clearly indicate the presence of a chlorine atom in this
by-product.
Merck Inc. Visualization of spots on TLC plates was done
by use of UV light. Mixtures of ethyl acetate and hexanes
were used as eluants. Purification by radial thin-layer
chromatography were performed on a Model 7924T
Chromatotron from Harrison Research, Palo Alto. The
plates (1, 2, and 4 mm thickness) were coated with EM
Reagents silica gel 60 PF254 containing gypsum.
Furthermore, we found that silylcyclopropane 15 underwent
fragmentation upon treatment with all four Lewis acids.
Hexaethyldisiloxane was isolated in 77–94% yields and
4-nitro-1-butene (16)18,19 in 58–72% yields (entries 18–21
in Table 1).
Proton NMR spectra were obtained on a Varian Unity-400
(400 MHz) spectrometer by use of chloroform-d as solvent
and tetramethylsilane as internal standard. Carbon-13 NMR
spectra were obtained on a Varian Unity-400 (100 MHz)
spectrometer by use of chloroform-d as solvent. Carbon-
13 chemical shifts are referenced to the center of the
CDCl3 triplet (d 77.0 ppm). Multiplicities are recorded by
the following abbreviations: s, singlet; d, doublet; t, triplet;
q, quartet; m, multiplet; J, coupling constant (hertz). Infra-
red (IR) spectra were measured on a Bomem Michelson
Series FT-IR spectrometer. The wave numbers reported
are referenced to the polystyrene 1601 cmϪ1 absorption.
Absorption intensities are recorded by the following abbre-
viations: s, strong; m, medium; w, weak. Low resolution
mass spectral analyses were performed on a Hewlett-
Packard 5890 Series II instrument equipped with a
Hewlett-Packard 5971A Mass Selective Detector and a
capillary HP-1 column. High-resolution mass spectra were
obtained by means of a JEOL JMS-HX110 mass spectro-
meter.
Conclusions
Our results from a systematic study indicate that aliphatic
nitro compounds can be activated by having two or more of
the following structural features: angle strain, g, d-unsatu-
ration, and a g-silyl group. Upon treatment with an appro-
priate Lewis acid, these activated nitro compounds often
underwent fragmentation to give products of various
classes.
Experimental
General procedure
All reactions were carried out in oven-dried glassware
(120ЊC) under an atmosphere of nitrogen. Tetrahydrofuran
(reagent grade) from Mallinckrodt was dried by distillation
from sodium and benzophenone. Dichloromethane, ethyl
acetate, and hexanes from Mallinckrodt Chemical Co.
were dried and distilled from CaH2. Dimethyl sulfoxide
from Aldrich was dried and distilled from CaH2 and stored
in serum-capped bottles under argon over molecular sieves
4A. trans-b-Nitrostyrene, triethylsilyl chloride, (trimethyl-
silyl)methylmagnesium chloride, and trimethylsulfoxonium
iodide were purchased from Aldrich Chemical Co. Alu-
minum chloride, boron trifluoride diethyl etherate, cyclo-
pentadiene, sodium, sodium hydride, tin(IV) chloride, and
titanium(IV) chloride were purchased from Merck Inc.
2-endo-Nitrobicyclo[2.2.1]heptane,10 2-endo-nitrobicyclo-
[2.2.1]-hept-5-ene,12 nitroethylene,12 trans-1-nitro-2-phenyl-
cyclopropane,15 1-nitro-2-phenylpropane,9 trans-1-nitro-3-
(triethylsilyl)-1-propene,20 2-[(trimethylsilyl)methyl]-1-nitro-
cyclohexane,10 7-anti-(trimethylsilyl)-2-nitrobicyclo[2.2.1]-
heptane,10 and 7-syn-(trimethylsilyl)-2-endo-nitrobicyclo-
[2.2.1]hept-5-ene12 were prepared by literature methods.
The final products were purified as stated; their purity was
Ͼ99.5% as determined by GC.
1-Nitro-2-phenyl-3-(trimethylsilyl)propane (2). A solution
of trans-b-nitrostyrene (1.12 g, 7.49 mmol, 1.0 equiv.) in
THF (5.0 mL) was added dropwise to a solution of
(trimethylsilyl)methylmagnesium chloride (1.00 M in
ether, 9.74 mL, 9.74 mmol, 1.30 equiv.) in THF (3.0 mL)
at Ϫ20ЊC. After the solution was stirred at the same
temperature for 15 min, ice–water (15 mL) and ether
(150 mL) were added into the reaction flask to quench the
reaction. This solution was neutralized with 3.5% aqueous
HCl (12 mL). At the end-point of acidification, the aqueous
layer became colorless. The ether layer was washed with
saturated aqueous NaHCO3 (25 mL×2) and the aqueous
layer was back extracted with Et2O (15 mL×5). The
combined etheral solutions were washed with saturated
aqueous NaCl (25 mL), dried over MgSO4 (s), filtered,
and concentrated under reduced pressure to give a light
green oil. The oil was purified by use of a Chromatotron
(4 mm plate, 1% EtOAc in hexanes as eluant) to give pure 2
(1.65 g, 6.97 mmol) as a light green oil in 93% yield: GC tR
14.74 min; TLC Rf 0.59 (5% EtOAc in hexanes); dH
(CDCl3) 0.01 (s, 9H, 3×CH3), 1.12 (d, Jˆ7.9 Hz, 2H,
CH2Si), 3.78 (m, 1H, PhCH), 4.68 (d, Jˆ8.0 Hz, 2H,
CH2N), 7.39–7.50 (m, 5H, PhH); nmax (film)/cmϪ1 3040
(m, Ph), 2954 (s, C–H), 2884 (s, C–H), 1605 (w, Ph),
1551 (s, NO2), 1378 (s, NO2), 1250 (s, Si–C), 850 (s), 764
(m, Ph), 700 (s, Ph) cmϪ1; m/z (EI) 237.1192 (C12H19NO2Si
Melting points were obtained with a Bu¨chi 535 melting
point apparatus. Gas chromatographic analyses were
performed on a Hewlett-Packard 5890 Series II instrument
equipped with a 25 m cross-linked methyl silicone gum
capillary column (0.32 mm i.d.). Nitrogen gas was used as
a carrier gas and the flow rate was kept constant at 14.0 mL/
min. The retention time tR was measured under the follow-
ing conditions: injector temperature 260ЊC, the initial
temperature for column 70ЊC, duration 2.00 min, increment
rate 10ЊC/min, and the final temperature for column 250ЊC.
Analytical thin layer chromatography (TLC) was performed
on precoated plates (silica gel 60 F-254), purchased from
⅐ϩ
requires 237.1185), 222 (M Ϫ15, 2%), 190 (10), 118 (11),
117 (18), 105 (9), 104 (100), 103 (8), 91 (13), 75 (16), 73 (72).
7-syn-(Triethylsilyl)-2-endo-nitrobicyclo[2.2.1]hept-5-ene
(9). A solution of freshly cracked cyclopentadiene (838 mg,
12.7 mmol, 1.0 equiv.) in THF (3.0 mL) was added drop-
wise at room temperature to a stirred suspension of sodium
sand14 (340 mg, 13.9 mmol, 1.1 equiv.) and THF (8.0 mL).

D.-N. Horng et al. / Tetrahedron 56 (2000) 1631–1636
1635
The reaction was stirred for 4.0 h, the resultant red mixture
was cooled to 0ЊC. To this mixture was added dropwise a
solution of triethylsilyl chloride (2.09 g, 13.9 mmol
1.1 equiv.) in THF (4.0 mL). After the reaction mixture
was stirred at 0–5ЊC for 5.0 h, it was cautiously treated
with ice–water (15 mL) and extracted with ether
(10 mL×3). The combined organic layers were washed
with water (10 mL×2), dried over MgSO4 (s), filtered, and
concentrated under reduced pressure to give a pale yellow oil.
equiv.) in dichloromethane (1.0 mL) was added dropwise
a solution of nitro compound (1.01 mmol, 1.0 equiv.) in
dichloromethane (0.55 mL) at 0ЊC. The reaction mixture
was allowed to warm to room temperature and stirred for
72 h, unless otherwise indicated. Ice–water (10 mL) and
ether (30 mL) were then added into the reaction flask. The
organic layer was washed with saturated aqueous NaHCO3
(15 mL×2) and the aqueous layer was back extracted with
Et2O (15 mL×3). The combined etheral solutions were
washed with saturated aqueous NaCl (25 mL), dried over
MgSO4 (s), filtered, and concentrated under reduced
pressure. The residue was purified by use of a Chromatotron.
A solution of nitroethylene (1.48 g, 20.3 mmol, 1.6 equiv.)
in ether (15 mL) was added dropwise to an ice-cooled and
stirred ether solution of 5-(triethylsilyl)cyclopentadiene that
was prepared as described above. The reaction mixture was
stirred overnight, the solvents were evaporated, and the
residue was purified by use of a Chromatotron (2 mm
plate, 1% EtOAc in hexanes as eluant) to give pure 9
(739 mg, 2.92 mmol) as a light yellow oil in 23% yield
(based on cyclopentadiene used): GC tR 16.42 min; TLC
Rf 0.55 (10% EtOAc in hexanes); dH (CDCl3) 0.45 (q,
Jˆ7.8 Hz, 6H, 3×SiCH2), 0.81 (t, Jˆ7.8 Hz, 9H, 3×CH3),
1.10 (s, 1H, SiCH), 1.83 (m, 1H), 2.13 (m, 1H), 3.04 (m,
1H), 3.59 (m, 1H), 5.00 (m, 1H, CHN), 5.81 (dd, Jˆ5.7,
3.0 Hz, 1H, yCH), 6.30 (dd, Jˆ5.7, 2.8 Hz, 1H, yCH); nmax
(film)/cmϪ1 3093 (w, yC–H), 2953 (s, C–H), 2917 (s, C–
H), 2875 (s, C–H), 1544 (s, NO2), 1457 (m), 1376 (s, NO2),
1241 (m, Si–C), 1016 (m), 718 (s) cmϪ1; m/z (EI) 253.1489
cis-6-Cyclopentena[e]tetrahydro-1,2-oxazin-3-one (7) from
2-endo-Nitrobicyclo[2.2.1]-hept-5-ene (6). The standard
procedure was followed by use of titanium(IV) chloride
(383 mg, 2.02 mmol, 2.0 equiv.) and 6 (140 mg, 1.01
mmol, 1.0 equiv.). After the reaction mixture was stirred
at 0ЊC for 10 min, it was worked up and the residue was
purified by use of a Chromatotron (1 mm plate, 7% EtOAc
in hexanes as eluant) to give pure 7 (59.0 mg, 0.424 mmol)
as a pale yellow oil in 42% yield: GC tR 9.31 min; TLC Rf
0.29 (30% EtOAc in hexanes); dH (CDCl3) 2.29 (m, 2H,
yCCH2), 2.78 (m, 2H, COCH2), 3.13 (m, 1H, CH), 5.50
(m, 1H, CHO), 5.86 (m, 1H, yCH), 6.06 (m, 1H, yCH);
nmax (film)/cmϪ1 3479 (m, N–H), 3041 (w, yC–H), 2962 (s,
C–H), 2936 (s, C–H), 2855 (m, C–H), 1766 (s), 1676 (m,
CyO), 1362 (m), 1173 (s), 1012 (m) cmϪ1; m/z (EI) 124
⅐ϩ
(C13H23NO2Si requires 253.1498), 224 (M Ϫ29, 2%), 196
⅐ϩ
(31), 194 (39), 166 (16), 165 (28), 132 (100), 104 (43), 103
(M Ϫ15, 9%), 95 (2), 81 (2), 80 (74), 79 (100), 77 (7), 67
(68), 91 (13), 87 (13).
(5), 65 (1), 53 (3), 51 (1).
trans-2-[(Triethylsilyl)methyl]-1-nitrocyclopropane (15).
A solution of trimethylsulfoxonium iodide (281 mg,
1.28 mmol, 1.1 equiv.) in DMSO (5.0 mL) was added
dropwise to a stirred suspension of sodium hydride
(30.7 mg, 1.28 mmol, 1.1 equiv.) in DMSO (1.0 mL).
After the mixture was stirred at room temperature for
4.0 h, it became clear. The solution was then cooled to
10ЊC and a solution of trans-1-nitro-3-(triethylsilyl)-1-
propene (233 mg, 1.16 mmol, 1.0 equiv.) in DMSO
(0.50 mL) was added dropwise. The mixture was stirred at
50ЊC in an oil bath for 4.0 h and then at room temperature
for 12 h. Ice–water (10 mL) and ether (100 mL) were added
into the reaction mixture. The ether layer was washed with
water (15 mL×3), saturated aqueous NaCl (15 mL), dried
over MgSO4 (s), filtered, and concentrated under reduced
pressure. The residue was purified by use of a Chromatotron
(2 mm plate, 2% EtOAc in hexanes as eluant) to give pure
15 (192 mg, 0.893 mmol) as a light green oil in 77% yield:
GC tR 13.76 min; TLC Rf 0.53 (10% EtOAc in hexanes); dH
(CDCl3) 0.42 (m, 1H), 0.56 (q, Jˆ7.8 Hz, 6H, 3×SiCH2),
0.86 (m, 1H), 0.92 (t, Jˆ7.8 Hz, 9H, 3×CH3), 1.01 (m, 1H),
1.88 (m, 2H), 3.97 (m, 1H, CHN); nmax (film)/cmϪ1 2955 (s,
C–H), 2914 (s, C–H), 2876 (s, C–H), 1543 (s, NO2), 1460
(m), 1366 (m, NO2), 1238 (m, Si–C), 1073 (s), 1010 (s), 737
(s) cmϪ1; m/z (EI) 215.1348 (C10H21NO2Si requires
5-(2-Nitroethyl)cyclopentadiene (10) from 7-syn-(Tri-
methylsilyl)-2-endo-nitrobicyclo-[2.2.1]hept-5-ene (8). The
standard procedure was followed by use of aluminum
chloride (267 mg, 2.02 mmol, 2.0 equiv.) and 8 (213 mg,
1.01 mmol, 1.0 equiv.). After the reaction mixture was
stirred at 0ЊC for 5.0 min, it was worked up and the residue
was purified by use of a Chromatotron (1 mm plate, 2%
EtOAc in hexanes as eluant) to give pure 10 (139 mg,
0.999 mmol) as a pale yellow oil in 99% yield: GC tR
8.67 min; TLC Rf 0.42 (10% EtOAc in hexanes); dH
(CDCl3) 2.91–3.13 (m, 3H), 4.54 (t, Jˆ7.2 Hz, 2H,
CH2N), 6.32 (m, 4H, yCH); dC (CDCl3) 28.42, 43.20,
75.09, 129.41, 132.26; nmax (film)/cmϪ1 3060 (m, yC–H),
2963 (s, C–H), 2925 (s, C–H), 2849 (m, C–H), 1651 (m,
CyC), 1556 (s, NO2), 1435 (s), 1379 (s, NO2), 1088 (w), 870
(m) cmϪ1; m/z (EI) 139.0624 (C7H9NO2 requires 139.0633),
⅐ϩ
139 (M , 16%), 93 (15), 92 (89), 91 (100), 79 (7), 78 (18),
77 (39), 65 (15), 53 (5), 51 (5).
5-(2-Nitroethyl)cyclopentadiene (10) from 7-syn-(tri-
ethylsilyl)-2-endo-nitrobicyclo-[2.2.1]hept-5-ene (9). The
above procedure was followed except that 9 (256 mg,
1.01 mmol, 1.0 equiv.) was used to replace 8. After purifi-
cation, pure 10 (94.1 mg, 0.989 mmol) was obtained in 98%
yield.
⅐ϩ
215.1341), 186 (M Ϫ29, 2%), 132 (48), 115 (66), 104
(24), 103 (35), 87 (100), 75 (77), 63 (22), 59 (51), 54 (18).
Hexaethyldisiloxane from 7-syn-(Triethylsilyl)-2-endo-
nitrobicyclo[2.2.1]hept-5-ene (9). The standard procedure
was followed by use of titanium(IV) chloride (383 mg,
Standard procedure for reaction of nitro compounds
with a Lewis acid
2.02 mmol, 2.0 equiv.) and
9 (255 mg, 1.01 mmol,
1.0 equiv.). After the reaction mixture was stirred overnight,
it was worked up and the residue was purified by use of a
To a stirred suspension of a Lewis acid (2.02 mmol, 2.0

1636
D.-N. Horng et al. / Tetrahedron 56 (2000) 1631–1636
Chromatotron (1 mm plate, hexanes as eluant) to give pure
hexaethyldisiloxane (102 mg, 0.414 mmol) as a colorless oil
in 82% yield: GC tR 11.41 min; TLC Rf 0.99 (hexanes);
dH (CDCl3) 0.52 (q, Jˆ8.0 Hz, 12H, 6×CH2), 0.94 (t,
Jˆ8.0 Hz, 18H, 6×CH3); nmax (film)/cmϪ1 2955 (s, C–H),
2902 (s, C–H), 2876 (s, C–H), 1458 (m), 1414 (m), 1238
hexaethyldisiloxane (95.7 mg, 0.389 mmol) in 77% yield;
and by tin(IV) chloride (526 mg, 2.02 mmol, 2.0 equiv.), 16
(68.4 mg, 0.677 mmol) was obtained in 67% yield and
hexaethyldisiloxane (107 mg, 0.434 mmol) in 86% yield.
The spectroscopic and physical data of 16 are consistent
with those reported.18,19
(m, Si–C), 1074 (s, Si–O), 1004 (s), 741 (s), 665 (m) cmϪ1
;
⅐ϩ
m/z (EI) 246 (M , 0.5%), 218 (21), 217 (100), 190 (14), 189
(71), 161 (43), 133 (16), 105 (21), 103 (13), 59 (11).
Acknowledgements
5-Phenyl-3-isoxazolidinone (13) from trans-1-nitro-2-
phenylcyclopropane (12). The standard procedure was
followed by use of tin(IV) chloride (526 mg, 2.02 mmol,
2.0 equiv.) and 12 (165 mg, 1.01 mmol, 1.0 equiv.). After
the reaction mixture was stirred overnight, it was worked up
and the residue was purified by use of a Chromatotron
(1 mm plate, 80% EtOAc in hexanes as eluant) to give
pure 13 (128 mg, 0.788 mmol) as yellow solid in 78%
yield: mp 127–129ЊC; GC tR 13.25 min; TLC Rf 0.08
(80% EtOAc in hexanes); dH (CDCl3) 2.81–2.97 (m, 2H,
CH2), 5.24 (dd, Jˆ11, 6.8 Hz, 1H, CH), 7.24–7.36 (m, 5H,
PhH); nmax (film)/cmϪ1 3419 (m, N–H), 3041 (m, Ph), 2917
(m, C–H), 1713 (s, CyO), 1630 (w, Ph), 1455 (m), 1281
(m), 1062 (m), 763 (m, Ph), 700 (s, Ph) cmϪ1; m/z (EI)
For financial support, we thank the National Science
Council of the Republic of China.
References
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Maggi, R.; Sartori, G. J. Chem. Soc., Dalton Trans. 1993, 1463.
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⅐ϩ
163.0626 (C9H9NO2 requires 163.0633), 148 (M Ϫ15,
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5-Phenyl-3-isoxazolidinone (13) and 3-chloro-3-phenyl-
propionohydroxamic acid (14) from trans-1-nitro-2-
phenylcyclopropane (12). The standard procedure was
followed by use of aluminum chloride (267 mg,
2.02 mmol, 2.0 equiv.) and 12 (165 mg, 1.01 mmol,
1.0 equiv.). After the reaction mixture was stirred for
30 min, it was worked up and the residue was purified by
use of a Chromatotron (1 mm plate, 80% EtOAc in hexanes
as eluant) to give pure 13 (78.8 mg, 0.485 mmol) in 48%
yield and pure 14 (46.2 mg, 0.232 mmol) as a yellow solid
in 23% yield. For 14: mp 174–176ЊC; GC tR 11.60 min;
TLC Rf 0.39 (80% EtOAc in hexanes); dH (CDCl3) 2.02
(br, 1H, OH) 3.15 (dd, Jˆ15, 6.0 Hz, 1H), 3.31 (dd,
Jˆ15, 8.8 Hz, 1H), 5.27 (dd, Jˆ8.8, 6.0 Hz, 1H, CHCl),
7.30–7.41 (m, 5H, PhH), 8.44 (br, 1H, NH); dC (CDCl3)
46.46, 58.48, 126.95, 128.82, 128.99, 137.64, 139.58; nmax
(film)/cmϪ1 3605 (m, O–H), 3315 (s, N–H), 3040 (m, Ph),
2919 (m, C–H), 1638 (s, CyO), 1601 (m), 1454 (s), 1122 (s),
765 (m, Ph), 698 (s, Ph) cmϪ1; m/z (EI) 181.0309 (C9H8ClNO
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⅐ϩ
requires 181.0294), 181 (M Ϫ18, 11%), 128 (7), 127 (32),
126 (7), 125 (100), 103 (5), 90 (5), 89 (15), 63 (6), 56 (6).
4-Nitro-1-butene (16) and hexaethyldisiloxane from
trans-2-[(triethylsilyl)methyl]-1-nitrocyclopropane (15).
The standard procedure was followed by use of 15 (217
mg, 1.01 mmol, 1.0 equiv.) and four different Lewis acids,
respectively. By use of aluminum chloride (267 mg,
2.02 mmol, 2.0 equiv.), 16 (73.5 mg, 0.727 mmol) was
obtained in 72% yield and hexaethyldisiloxane (117 mg,
0.475 mmol) in 94% yield; by titanium(IV) chloride
(383 mg, 2.02 mmol, 2.0 equiv.), 16 (67.4 mg, 0.667
mmol) was obtained in 66% yield and hexaethyldisiloxane
(98.1 mg, 0.399 mmol) in 79% yield; by boron trifluoride
diethyl etherate (287 mg, 2.02 mmol, 2.0 equiv.), 16
(59.2 mg, 0.586 mmol) was obtained in 58% yield and
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