A convenient synthetic method of isoxazole derivatives using copper(II) nitrate

Article abstract of DOI:10.3987/COM-14-12979

3-Acetylisoxazoles were synthesized by the reaction of alkenes or alkynes in acetone as solvent with copper(II) nitrate and formic acid. In the case of ethyl acetate as solvent, 3-benzoylisoxazoles were yielded by the reaction of alkynes and acetophenone

Full text of DOI:10.3987/COM-14-12979

HETEROCYCLES, Vol. 89, No. 6, 2014
1473
HETEROCYCLES, Vol. 89, No. 6, 2014, pp. 1473 - 1482. © 2014 The Japan Institute of Heterocyclic Chemistry
Received, 13th March, 2014, Accepted, 16th April, 2014, Published online, 25th April, 2014
DOI: 10.3987/COM-14-12979
A CONVENIENT SYNTHETIC METHOD OF ISOXAZOLE
DERIVATIVES USING COPPER(II) NITRATE
Ken-ichi Itoh,1* Tadashi Aoyama,2 Hiroaki Satoh,2 Kenta Hasegawa,2
Natsumi Meguro,2 Akira C. Horiuchi,3 Toshio Takido,2 and Mitsuo
Kodomari4
1
Department of Liberal Arts and Science, College of Science and Technology,
2
Nihon University, 7-24-1 Narashinodai, Funabashi-shi, Chiba 274-8501, Japan.
Department of Materials and Applied Chemistry, College of Science and
Technology, Nihon University, Kanda Surugadai, Chiyoda-ku, Tokyo 101-8303,
3
Japan. Department of Chemistry, College of Science, Rikkyo (St. Paul’s)
University, 3-34-1 Nishi-ikebukuro, Toshima-ku, Tokyo 171-8501, Japan. 4 The
Institute of Natural Sciences, College of Humanities and Sciences, Nihon
University, 3-25-40 Sakurajosui, Setagaya-ku, Tokyo 156-8550, Japan. e-mail:
k-itoh@chem.ge.cst.nihon-u.ac.jp
Abstract – 3-Acetylisoxazoles were synthesized by the reaction of alkenes or
alkynes in acetone as solvent with copper(II) nitrate and formic acid. In the case
of ethyl acetate as solvent, 3-benzoylisoxazoles were yielded by the reaction of
alkynes and acetophenone with copper(II) nitrate and nitric acid. This synthetic
method provides a convenient production of isoxazole derivatives.
Isoxazole derivatives, five-membered nitrogen-containing heterocycles, are an important class of
heterocyclic compounds. They can be converted into a number of useful synthetic units by the reductive
ring cleavage, such as β-hydroxy ketones1 or γ-amino alcohols.2 Moreover, many compounds bearing the
isoxazole moieties show relevant biological activity: very late antigen-4 (VLA-4) antagonist3 and
cyclooxygenase-1 (COX-1) inhibitor.4 Isoxazole derivatives are synthesized according to an
intermolecular [3+2] cycloaddition reaction between alkenes (or alkynes) and nitrile oxides.5 Nitrile
oxides are generally prepared from aldoximes by following two steps: halogenation of aldoxime (into
hydroximoyl halide) and dehydrohalogenation using base.6
We have recently reported that a newly synthetic method of isoxazole derivatives using ammonium
cerium nitrate (CAN)7 or iron(III) nitrate.8 3-Acetyl- and 3-benzoylisoxazoles were synthesized by the

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HETEROCYCLES, Vol. 89, No. 6, 2014
reaction of alkenes (or alkynes) with acetone or acetophenone as solvent in the presence of CAN or
iron(III) nitrate involving the nitrile oxide intermediate generated from ketones. Although the reaction
using CAN proceeded, the reaction using iron(III) nitrate was inexpensive and non-toxic synthetic
method of isoxazole derivatives. The synthetic method using iron(III) nitrate is a simple production of
isoxazole derivatives, however, the use of iron(III) nitrate has drawbacks: the resulting brown color of
iron salts after the reaction was made difficult to isolate the product from reaction mixture. In addition,
since ketone was employed as solvent, it was necessary to remove ketone from the reaction mixture. Here,
we wish to report a convenient method for the synthesis of 3-acetyl- and 3-acylisoxazoles using
copper(II) nitrate rather than the reaction using CAN or iron(III) nitrate. Copper(II) nitrate is inexpensive
and non-toxic reagent compared with CAN, and the resulting dark green color of copper salts after the
reaction was easily dissolved by the addition of dilute hydrochloric acid. Moreover, since the quantity of
ketone was limited to the amount of substrate by the use of ethyl acetate as solvent, 3-benzoylisoxazoles
were obtained from the reaction of alkynes and acetophenone as substrate with copper(II) nitrate and
nitric acid in ethyl acetate. The present method is afforded to a simple and efficient synthesis of isoxazole
derivatives.
At first, the reaction of 1-octene 1a (R1 = n-C6H13) with copper(II) nitrate in acetone 2a under reflux for
24 h was carried out (Scheme 1 and Table 1).
Scheme 1
Table 1. The reaction of 1-octene 1a with copper(II) nitrate in acetone 2a
Cu(NO3)2
Yield (%)b
Entrya
(Mol. equiv.)
1a
3a
18
22
30
28
18
1
2
3
4
5
0.5
1.0
1.5
2.0
4.0
58
38
14
4
NDc
a1a (0.5 mmol), copper(II) nitrate (0.25-2.0 mmol) and 2a (5 mL) were employed.
bDetermined by GLC analysis using n-dodecane as an internal hydrocarbon
standard. bNot detected.

HETEROCYCLES, Vol. 89, No. 6, 2014
1475
3-Acetyl-5-hexyl-4,5-dihydroisxoazole 3a was obtained in low yield (about 20-30% yields). It seems that
the production of isoxazole derivative was inhibited by the formation of copper complex from copper and
reaction intermediate. In order to improve the yield of 3a, we further examined the reactions adding
several carboxylic acids (Table 2).
Table 2. The addition of several acids
Cu(NO3)2
(Mol. equiv.)
1.0
Yield (%)b
Entrya
Acid
Mol. equiv.
1a
3a
53
72
80
80
62
72
58
54
55
55
51
60
62
65
ND
65
58
25
23
24
1
2
HCO2H
HCO2H
HCO2H
HCO2H
HCO2H
HCO2H
HCO2H
AcOH
2.5
5.0
NDc
ND
ND
ND
18
1.0
3
1.0
7.5
4
1.0
10.0
10.0
10.0
10.0
5.0
5
0.5
6
1.5
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
44
7
2.0
8
1.0
9
1.0
AcOH
10.0
15.0
10.0
10.0
10.0
10.0
1.0
10
11
12
13
14
15
16
17
18
19
20
1.0
AcOH
1.0
EtCO2H
PhCO2H
ClCH2CO2H
Cl3CCO2H
H2SO4
1.0
1.0
1.0
1.0
1.0
H2SO4
1.5
1.0
H2SO4
2.5
1.0
H2SO4
5.0
1.0
HCl
1.0
1.0
HCl
2.5
12
a1a (0.5 mmol), copper(II) nitrate (0.25-1.0 mmol), acid (0.5-7.5 mmol) and 2a (5 mL)
were employed under reflux for 24 h. bDetermined by GLC analysis using n-dodecane
as an internal hydrocarbon standard. cNot detected.
The yields of 3a increased into about 50-80% yields. In particular, when the reaction adding 7.5 molar
equivalent of formic acid was carried out, 3a was obtained in 80% GLC yield (Table 2, entry 3).
Although the reaction using sulfuric acid gave 3a in about 60% yield (Entries 16 and 17), it was clearly
that the formation of 3a effectively proceeded by the addition of formic acid.
Therefore, the reaction of several alkenes in the presence of copper(II) nitrate and formic acid was
performed in acetone under reflux. The results were summarized in Table 3.

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HETEROCYCLES, Vol. 89, No. 6, 2014
Table 3. The reaction of several alkenes 1a-1i with copper(II) nitrate and formic acid in acetone 2a
Entry
Substrate
R1
n-C6H13
n-C8H17
n-C10H21
t-C4H9
Yield / %a
3a (76)
3b (82)
3c (63)
3d (65)
3e (64)
3f (64)
1
1a
1b
1c
1d
1e
1f
2
3
4
5
CN
6
CH2OCOMe
cyclo-C6H11
CH2Cl
7
1g
1h
1i
3g (82)
3h (64)
3i (46)
8
9
CH2Br
aIsolated yields.
In addition, the reaction of disubstituted alkenes was carried out. In the case of cyclohexene 1j, the
corresponding 4,5-disubstituted isoxazole derivative 3j was obtained in 19% yield (Scheme 2).
Scheme 2
The reaction of 2-ethyl-1-butene 1k and methylenecyclohexane 1l as 1,1-disubstituted alkenes gave the
corresponding 5,5-disubstituted isoxazole derivatives 3k and 3l in 13 and 13% yields, respectively
(Scheme 3).
Scheme 3
The yield of the product from disubstituted alkenes was lowered compared with the reaction of terminal
alkenes. We further examined the reaction of several alkynes in the presence of copper(II) nitrate and
formic acid in acetone (Scheme 4 and Table 4).
Scheme 4

HETEROCYCLES, Vol. 89, No. 6, 2014
1477
Table 4. In the case of several alkynes 4a-4i
Entry
Substrate
R4
n-C6H13
n-C8H17
Ph
Yield / %a
5a (87)
5b (85)
5c (39)
5d (95)
5e (67)
5f (83)
1
4a
4b
4c
4d
4e
4f
2
3
4
CO2C2H5
SiMe3
5
6
CH2Cl
7
4g
4h
4i
CH2Br
5g (74)
5h (91)
5i (92)
8
CMe2OH
cyclo-C6H10-1-OH
9
aIsolated yields.
The present method is a simple and convenient synthesis of 3-acetylisoxazoles, however, since ketone
was employed as solvent, it was difficult to apply to the reaction by the use of high boiling ketones. In
order to solve the problem, we investigated the reaction using several solvent: chloroform, acetic
anhydride, tetrahydrofuran, 1,4-dioxane, ethyl acetate, pyridine, and dimethyl sulfoxide (Scheme 5, Table
5). Among them, it was found that the reaction of 1-octyne 4a and acetophenone 2b (R5 = Ph) in the
presence of copper(II) nitrate in ethyl acetate afforded to 3-benzoyl-5-hexylisoxazole 6a (Table 3, Entry
6).
Scheme 5
Table 5. The reaction of 1-octyne 4a and acetophenone 2b with copper(II) nitrate in several solvent
Entrya
Solvent
H2O
Temp./C°
Yield of 6ab
1
2
3
4
5
6
7
8
80
60
80
60
80
60
80
80
NDc
ND
trace
trace
3
CHCl3
Ac2O
THF
1,4-dioxane
EtOAc
pyridine
DMSO
6
ND
ND
a4a (0.5 mmol), 2b (0.5 mmol), copper(II) nitrate (0.5 mmol) and solvent (5 mL) were employed
for 24 h. bDetermined by GLC analysis using n-dodecane as an internal hydrocarbon standard.
cNot detected.

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HETEROCYCLES, Vol. 89, No. 6, 2014
In the literature,7,8 we proposed the reaction mechanism: the corresponding nitrile oxide was transformed
from α-nitro ketone via the nitration of ketone. On the basis of our studies, we tried to the reaction adding
nitric acid (Table 6).
Table 6. The addition of nitric acid
4a
HNO3
Entrya
Yield of 6a (%)b
(mol. equiv.)
(mol. equiv.)
1
2
3
4
5
6
7
8
1
3
20
20
14
20
25
30
20
20
24
35
41
45
42
37
35
23
5
5
5
5
8
10
a4a (0.5-5.0 mmol), 2b (0.5 mmol), copper(II) nitrate (0.5 mmol), nitric acid (7-15 mmol)
and EtOAc (5 mL) were employed at 60 °C for 24 h. bDetermined by GLC
analysis using n-dodecane as an internal hydrocarbon standard.
The addition of nitric acid was improved the yield of the product into 24% GLC yield (Table 6, entry 1).
Furthermore, it was found that 6a was obtained in 45% GLC yield under optimum reaction condition
(Entry 4).
From the results, we carried out the reaction of alkynes and ketones in the presence of copper(II) nitrate
and nitric acid in ethyl acetate (Table 7).
Table 7. Reaction of alkynes and ketones 2b-2e with copper(II) nitrate and nitric acid in ethyl acetate
Run
Alkyne: R4
4a: n-C6H13
4c: Ph
Ketone: R5
Yield / %a
6a (44)
6b (46)
6c (89)
6d (83)
7a (39)
8a (39)
9a (16)
1
2b: Ph
2
2b: Ph
3
4i: cyclo-C6H10-1-OH
4j: CO2Me
2b: Ph
4
2b: Ph
5
4a: n-C6H13
4a: n-C6H13
4a: n-C6H13
2c: C6H4-4-Me
2d: C6H4-4-F
2e: 2-thienyl
6
7
aIsolated yields.
In conclusion, we developed a simple and efficient synthesis of 3-acetylisoxazoles by the use of
copper(II) nitrate. Moreover, we have succeeded the improvement of the synthesis of 3-benzoylisoxazoles

HETEROCYCLES, Vol. 89, No. 6, 2014
1479
by the use of ethyl acetate as solvent. These synthetic methods provide a convenient production of
isoxazole derivatives.
EXPERIMENTAL
Melting points were determined on a Yanako Micro melting point apparatus. The IR spectra were
1
recorded using a Thermo Electron Nicolet 380 spectrometer. The H and 13C NMR spectra were
measured using a JEOL JNM-GX400 spectrometer. Tetramethylsilane (δ=0) was used as an internal
1
standard for H NMR. Mass analysis was performed on an Agilent G1969LC/MDS TOF. All chemicals
were purchased from Tokyo Chemical Industry Co., Ltd, and Wako Pure Chemical Industries, Ltd.
Typical Procedure for the Preparation of 3-Acetylisoxazoles
A mixture of alkenes (or alkynes) (0.5 mmol), copper(II) nitrate trihydrate (0.5 mmol) and formic acid
(7.5 mol. equiv.; 3.75 mmol) in acetone (5 mL) was stirred under reflux for 18 h. The reaction mixture
was extracted with EtOAc (30 mL) and washed with 1 mol/L HCl (3 mL), aq. NaHCO3 solution (2x3
mL), saturated aq. sodium chloride solution (3 mL) and water (3 mL). The extract was dried over sodium
sulfate and was concentrated in vacuo after the filtration. The residue was chromatographed with EtOAc
and n-hexane on silica gel (Merck silica gel 60: 0.063-0.200 mm).
1
3-Acetyl-5-octyl-4,5-dihydroisoxazole (3b): a pale yellow oil; IR (neat) 2925, 2855, 1573 cm-1; H
NMR δ 0.88 (t, J = 6.8 Hz, 3H), 1.27-1.43 (m, 12H), 1.53-1.59 (m, 1H), 1.70-1.79 (m, 1H), 2.49 (s, 3H),
13
2.75 (dd, J = 8.2, 17.4 Hz, 1H), 3.15 (dd, J = 10.9, 17.4 Hz, 1H), 4.78 (m, 1H); C NMR δ 14.0, 22.6,
25.1, 26.6, 29.1, 29.2, 29.3, 31.7, 35.1, 36.6, 84.8, 158.2, 193.4; HRMS (TOF-Cl) calcd for C13H24NO2
(MH+): 226.1807. Found: 226.1817.
3-Acetyl-5-decyl-4,5-dihydroisoxazole (3c): a white solid; mp 34.1-34.3 °C; IR (neat) 2917, 2848, 1691,
1585 cm-1; 1H NMR δ 0.88 (t, J = 6.8 Hz, 3H), 1.26-1.43 (m, 16H), 1.53-1.59 (m, 1H), 1.70-1.79 (m, 1H),
2.49 (s, 3H), 2.75 (dd, J = 8.2, 17.4 Hz, 1H), 3.15 (dd, J = 10.9, 17.4 Hz, 1H), 4.78 (m, 1H); 13C NMR δ
14.0, 22.7, 25.1, 26.6, 29.3, 29.4, 29.5, 29.6, 29.6, 31.9, 35.1, 36.7, 84.9, 158.2, 193.4; HRMS (TOF-Cl)
calcd for C15H28NO2 (MH+): 254.2120. Found: 254.2119.
1
3-Acetyl-5-t-butyl-4,5-dihydroisoxazole (3d): a pale yellow oil; IR (neat) 2961, 1689, 1578 cm-1; H
NMR δ 0.93 (s, 9H), 2.48 (s, 3H), 2.88 (dd, J = 9.1, 17.9 Hz, 1H), 2.98 (dd, J = 11.5, 17.9 Hz, 1H), 4.50
(dd, J = 9.1, 11.5 Hz, 1H); 13C NMR δ 24.7, 26.5, 32.3, 34.1, 92.6, 158.2, 193.4; HRMS (TOF-Cl) calcd
for C9H16NO2 (MH+): 170.1181. Found: 170.1180.
1
3-Acetyl-5-cyano-4,5-dihydroisoxazole (3e): a pale brown oil; IR (neat) 3001, 1698, 1592 cm-1; H
13
NMR δ 2.55 (s, 3H), 3.55 (d, J = 9.2, 2H), 5.37 (t, J = 9.2 Hz, 1H); C NMR δ 27.0, 38.6, 68.3, 115.9,
157.0, 191.3; HRMS (TOF-Cl) calcd for C6H6N2O2 (MH+): 138.0429. Found: 138.0426.

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3-Acetyl-5-cyclohexyl-4,5-dihydroisoxazole (3g): a yellow oil; IR (neat) 2927, 2854, 1688, 1575 cm-1;
1H NMR δ 0.99-1.27 (m, 5H), 1.54-1.99 (m, 6H), 2.84 (dd, J = 9.2, 17.6 Hz, 1H), 3.05 (dd, J = 11.2, 17.6
Hz, 1H), 4.53 (m, 1H); 13C NMR δ 25.5, 25.6, 26.1, 26.5, 28.0, 28.2, 34.1, 42.2, 89.0, 158.2, 193.4;
HRMS (TOF-Cl) calcd for C11H18NO2 (MH+): 196.1337. Found: 196.1345.
1
3-Acetyl-5-chloromethyl-4,5-dihydroisoxazole (3h): a pale yellow oil; IR (neat) 1693, 1583 cm-1; H
NMR δ 2.51 (s, 3H), 3.11 (dd, J = 3.2, 18.2 Hz, 1H), 3.27 (dd, J = 11.2, 18.2 Hz, 1H), 3.44 (dd, J = 6.8,
13
10.8 Hz, 1H), 3.53 (dd, J = 4.0, 10.8 Hz, 1H), 5.05 (m, 1H); C NMR δ 26.4, 35.1, 44.5, 82.1, 157.6,
192.4; HRMS (TOF-Cl) calcd for C6H9NO2Cl (MH+): 162.0321. Found: 162.0319.
1
3-Acetyl-5-bromomethyl-4,5-dihydroisoxazole (3i): a pale yellow oil; IR (neat) 1692, 1583 cm-1; H
NMR δ 2.50 (s, 3H), 3.11 (dd, J = 3.2, 18.2 Hz, 1H), 3.27 (dd, J = 11.2, 18.2 Hz, 1H), 3.44 (dd, J = 6.8,
13
10.8 Hz, 1H), 3.53 (dd, J = 4.0, 10.8 Hz, 1H), 5.05 (m, 1H); C NMR δ 26.4, 35.1, 44.5, 82.1, 157.6,
192.4; HRMS (TOF-Cl) calcd for C6H9NO2Br (MH+): 205.9816. Found: 205.9823.
1
3-Acetyl-5,5-diethyl-4-hydroisoxazole (3k): a colorless oil; IR (neat) 2925, 1716, 1689, 1577 cm-1; H
NMR δ 0.91 (t, J = 7.3 Hz, 6H), 1.70 (q, J = 7.3 Hz, 4H), 2.48 (s, 3H), 2.84 (s, 2H); 13C NMR δ 7.7, 26.3,
30.6, 38.5, 94.9, 157.9, 193.7; HRMS (TOF-Cl) calcd for C9H16NO2 (MH+): 170.1181. Found: 170.1184.
1
3-Acetyl-5,5-spirohexyl-4-hydroisoxazole (3l): a yellow oil; IR (neat) 2936, 2859, 1688, 1574 cm-1; H
NMR δ 1.29-1.50 (m, 4H), 1.60-1.65 (m, 2H), 1.75-1.82 (m, 4H), 2.48 (s, 3H), 2.82 (s, 2H); 13C NMR δ
23.1, 24.7, 26.3, 36.3, 41.6, 91.5, 157.9, 193.8; HRMS (TOF-Cl) calcd for C10H16NO2 (MH+): 182.1181.
Found: 182.1184.
3-Acetyl-5-octylisoxazole (5b): a colorless oil; IR (neat) 2928, 2858, 1707, 1593 cm-1; 1H NMR δ 0.88 (t,
J = 7.3 Hz, 3H), 1.27-1.36 (m, 10H), 1.70 (quint., J = 7.3 Hz, 2H), 2.63 (s, 3H), 2.78 (t, J = 7.8 Hz, 2H),
13
6.35 (s, 1H); C NMR δ 14.1, 22.6, 26.6, 27.2, 27.3, 28.9, 29.0, 29.1, 31.7, 99.1, 162.1, 175.6, 192.4;
HRMS (TOF-Cl) calcd for C13H22NO2 (MH+): 224.1650. Found: 224.1660.
3-Acetyl-5-trimethylsilylisoxazole (5e): a yellow oil; IR (neat) 2962, 1705 cm-1; 1H NMR δ 0.36 (s, 9H),
13
2.68 (s, 3H), 6.81 (s, 1H); C NMR δ -2.0, 27.8, 110.9, 160.6, 180.4, 192.4; HRMS (TOF-Cl) calcd for
C8H14NO2Si(MH+): 184.0793. Found:184.0799.
3-Acetyl-5-chloromethylisoxazole (5f): a yellow oil; IR (neat) 3141, 2361, 1707, 1600 cm-1; 1H NMR δ
2.66 (s, 3H), 4.66 (s, 2H), 6.70 (s, 1H); 13C NMR δ 27.0, 33.8, 102.0, 161.9, 169.0, 191.3; HRMS
(TOF-Cl) calcd for C6H7NO2Cl (MH+): 160.0165. Found: 160.0174.
3-Acetyl-5-bromomethylisoxazole (5g): a yellow oil; IR (neat) 2360, 2341, 1704, 1595 cm-1; 1H NMR δ
2.65 (s, 3H), 4.50 (s, 2H), 6.68 (s, 1H); 13C NMR δ 17.8, 27.2, 102.1, 162.2, 169.1, 191.5; HRMS
(TOF-Cl) calcd for C6H7NO2Br (MH+): 203.9660. Found: 203.9667.
3-Acetyl-5-(1-hydroxy-1-methylethyl)-isoxazole (5h): a yellow oil; IR (neat) 3440, 2984, 2924, 1705,
1582 cm-1; 1H NMR δ 1.65 (s, 6H), 2.54 (brs., 1H), 2.64 (s, 3H), 6.53 (s, 1H); 13C NMR δ 27.2, 28.9, 69.0,

HETEROCYCLES, Vol. 89, No. 6, 2014
1481
97.8, 161.8, 179.6, 192.2; HRMS (TOF-Cl) calcd for C8H12NO3 (MH+): 170.0817. Found: 170.0824.
Typical Procedure for the Preparation of 3-benzoylisoxazoles
A mixture of alkynes (2.5 mmol), acetophenone (0.5 mmol), copper(II) nitrate trihydrate (0.5 mmol) and
nitric acid (10.0 mmol) in EtOAc (5 mL) was stirred at 60 °C for 24 h. The reaction mixture was
extracted with EtOAc (30 mL) and washed with 1 mol/L HCl (3 mL), aq. NaHCO3 solution (2x3 mL),
saturated aq. sodium chloride solution (3 mL) and water (3 mL). The extract was dried over sodium
sulfate and was concentrated in vacuo after the filtration. The residue was chromatographed with EtOAc
and n-hexane on silica gel (Merck silica gel 60: 0.063-0.200 mm).
3-Benzoyl-5-methoxycarbonylisoxazole (6d): a pale yellow solid; mp 82.6-83.5 °C; IR (neat) 3144,
1
1729, 1655, 1596 cm-1; H NMR δ 4.02 (s, 3H), 7.44 (s, 1H), 7.53-7.70 (m, 3H), 8.31-8.33 (m, 2H); 13C
NMR δ 53.1, 110.2, 128.7, 130.7, 134.4, 135.1, 156.6, 160.7, 162.1, 184.4; HRMS (TOF-Cl) calcd for
C12H10NO4 (MH+): 232.0604. Found: 232.0609.
1
3-(4-Methylbenzoyl)-5-hexylisoxazole (7a): a yellow oil; IR (neat) 2954, 2933, 1653, 1606 cm-1; H
NMR δ 0.90 (t, J = 7.3 Hz, 3H), 1.30-1.42 (m, 6H), 1.75 (quint., J = 7.3 Hz, 2H), 2.44 (s, 3H), 2.83 (t, J =
7.3 Hz, 2H), 6.50 (s, 1H), 7.31 (d, J = 8.2 Hz, 2H), 8.20 (d, J = 8.2 Hz, 2H); 13C NMR δ 14.0, 21.7, 22.4,
26.6, 27.3, 28.6, 31.3, 101.5, 129.2, 130.7, 133.3, 144.9, 161.9, 174.5, 185.7; HRMS (TOF-Cl) calcd for
C17H22NO2 (MH+): 272.1645. Found: 272.1653.
1
3-(4-Fluorobenzoyl)-5-hexylisoxazole (8a): a yellow oil; IR (neat) 2956, 2931, 1666, 1599 cm-1; H
NMR δ 0.90 (t, J = 7.3 Hz, 3H), 1.30-1.42 (m, 6H), 1.75 (quint., J = 7.3 Hz, 2H), 2.84 (t, J = 7.3 Hz, 2H),
13
6.52 (s, 1H), 7.17-7.21 (m, 2H), 8.37-8.40 (m, 2H); C NMR δ 14.0, 22.5, 26.6, 27.4, 28.6, 31.4, 101.6,
115.6, 115.8, 133.4, 133.5, 161.8, 174.9, 184.4; HRMS (TOF-Cl) calcd for C16H19NO2F (MH+): 276.1394.
Found: 276.1397.
3-(2-Thienylcarbonyl)-5-hexylisoxazole (9a): a yellow oil; IR (neat) 2954, 2929, 1685, 1644, 762, 725,
680, 630 cm-1; 1H NMR δ 0.89 (t, J = 7.3 Hz, 3H), 1.25-1.43 (m, 6H), 1.74 (quint., J = 7.3 Hz, 2H), 2.83
13
(t, J = 7.3 Hz, 2H), 6.52 (s, 1H), 7.20-7.22 (m, 1H), 7.78-7.79 (m, 1H), 8.43-8.45 (m, 1H); C NMR δ
13.9, 22.4, 26.5, 27.3, 28.6, 31.3, 101.0, 128.4, 135.8, 136.5, 141.6, 161.5, 174.9, 177.3; HRMS (TOF-Cl)
calcd for C14H18NO2S (MH+): 264.1052. Found: 264.1051.
ACKNOWLEDGEMENTS
This work was financially supported by the Nihon University College of Science and Technology
Grants-in-Aid for Fundamental Science Research.
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