Synthesis of 3-methylisoxazole-5-Carboxamides and 5-[(1H-pyrazol-1-yl)carbonyl]-3-methylisoxazoles

Article abstract of DOI:10.1081/SCC-120002127

The one-pot synthesis of six 3-methylisoxazole-5-carboxamides 2 [where the N-substituents are R¹ = H, Me and R² = PH, CH₂Ph, n-Bu, C(CH₃)₂Et, 3-methylisoxazol-5-yl] and twelve 5-[(1H-pyrazol-1-yl)carb

Full text of DOI:10.1081/SCC-120002127

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SYNTHESIS OF 3-METHYLISOXAZOLE- 5-
CARBOXAMIDES AND 5-[(1H-PYRAZOL-1-
YL)CARBONYL]- 3-METHYLISOXAZOLES
Marcos A. P. Martins a , Marcelo Neto a , Adilson P. Sinhorin a , Giovani P. Bastos a , Nilo E.
K. Zimmermann a , Adriano Rosa a , Helio G. Bonacorso a & Nilo Zanatta a
a Departamento de Química , Núcleo de Química de Heterociclos (NUQUIMHE) ,
Universidade Federal de Santa Maria , Santa Maria, RS, 97.105-900, Brazil
Published online: 16 Aug 2006.
To cite this article: Marcos A. P. Martins , Marcelo Neto , Adilson P. Sinhorin , Giovani P. Bastos , Nilo E. K. Zimmermann ,
Adriano Rosa , Helio G. Bonacorso & Nilo Zanatta (2002) SYNTHESIS OF 3-METHYLISOXAZOLE- 5-CARBOXAMIDES AND 5-
[(1H-PYRAZOL-1-YL)CARBONYL]- 3-METHYLISOXAZOLES, Synthetic Communications: An International Journal for Rapid
Communication of Synthetic Organic Chemistry, 32:3, 425-433
To link to this article: http://dx.doi.org/10.1081/SCC-120002127
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SYNTHETIC COMMUNICATIONS, 32(3), 425–433 (2002)
SYNTHESIS OF 3-METHYLISOXAZOLE-
5-CARBOXAMIDES AND
5-[(1H-PYRAZOL-1-YL)CARBONYL]-
3-METHYLISOXAZOLES
MarcosA. P. Martin,s * Marcelo Neto,
Adilson P. Sinhorin, Giovani P. Bastos,
Nilo E. K. Zimmermann, Adriano Rosa,
Helio G. Bonacorso, and Nilo Zanatta
Departamento de Quımica, Nucleo de Quımica
de Heterociclos (NUQUIMHE), Universidade Federal
de Santa Maria, 97.105-900 Santa Maria, RS, Brazil
ABSTRACT
The one-pot synthesis of six 3-methylisoxazole-5-carboxa-
mides 2 [where the N-substituents are R1 ¼ H, Me and
R2 ¼ Ph, CH2Ph, n-Bu, C(CH3)2Et, 3-methylisoxazol-5-yl]
and twelve 5-[(1H-pyrazol-1-yl)carbonyl]-3-methyl isoxazoles
3 and 4 [where the pyrazole substituents are R3 (C5/C3) ¼
CO2Et, CF3 and R5 (C3/C5) ¼ H, Me, Et, Ph] from the
3-methyl isoxazole-5-carboxylic acid, thionyl chloride and
the corresponding amine or pyrazole is reported. In the syn-
thesis of 5-[(1H-pyrazol-1-yl)carbonyl]-3-methylisoxazoles we
obtained a mixture of 1,3- and 1,5-isomers 3 and 4 in variable
*Corresponding author. E-mail: mmartins@base.ufsm.br; http://www.ufsm.br/
nuquimhe
425
Copyright & 2002 by Marcel Dekker, Inc.
www.dekker.com

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MARTINS ET AL.
ratios, i.e., the substituent R3 (CO2Et and CF3) are present in
position 3 or 5 on the pyrazole ring.
Isoxazole derivatives possess very interesting pharmacological pro-
perties, especially isoxazolecarbonyl compounds that show marked action
as diuretic,1 antiinflammatory, analgesic, antipyretic, anticoagulant, and
antireumatic. Isoxazolecarbonyl compounds are also important precursors
for the synthesis of other compounds such as agrochemicals and micro-
bicides.2 As a part of our research program, we developed a general one-
step procedure for preparing a series of analytically pure 4-alkoxy-1,1,
1-trihalo-3-alken-2-ones, from the acylation of several enol ethers (or
acetals), in molar quantities.3 These compounds have been used as precursors
of a variety of substituted five-, six- and seven-membered heterocyclic
compounds, e.g., isoxazoles,3,4 pyrazoles,5 pyrimidines6 and diazepines.7
Recently,8 we reported a one-pot synthesis of isoxazole-5-carboxylic acids
from the cyclocondensation of 4-alkoxy-1,1,1-trichloro-3-alken-2-ones with
hydroxylamine, in hydrochloric acid or sulfuric acid medium. The aim of this
work is to show the one-pot synthesis of a series 3-methylisoxazole-5-carbox-
amides (2) and 5-[(1H-pyrazol-1-yl)carbonyl]-3-methylisoxazoles (3, 4) from
the 3-methyl isoxazole-5-carboxylic acid (1), thionyl chloride and the corre-
sponding amine or pyrazole (scheme).
3-Methylisoxazole-5-carboxylic acid (1) was synthesized from the
cyclocondensation reaction of 4-alkoxy-1,1,1-trichloro-3-alken-2-ones with
hydroxylamine in sulfuric acid.8 The 3(5)-trifluoromethylpyrazoles and pyr-
azole-3(5)-carboxylic acid ethyl ester were synthesized according as previous
report.5 The preparation of 3-methylisoxazole-5-carbonyl chloride from 1
was carried out with an excess of thionyl chloride and catalytic amounts of
pyridine, following by reflux for 16 h.
Compounds 2a–f were obtained by addition of amines to equimolar
amounts of 3-methylisoxazole-5-carbonyl chloride, obtained in situ. The
mixture was stirred for 12 h at 60ꢀC, and isolated products were recrystal-
lized. Compounds 3a–d and 4a–d were obtained by addition of pyrazoles to
3-methylisoxazole-5-carbonyl chloride as described for 2 with chloroform as
solvent. The mixture was stirred for 12 h at reflux. The recrystallized prod-
1
ucts were identified by H and 13C NMR spectroscopy.
The assignments of Z- and E-isomers in the carboxamide group of
2a–f were done based on the literature data.9 Then, we assign compounds
2a–e as E-isomer and 2f shown a 1 : 1 mixture of Z- and E-isomers.
The assignments of 1,3- and 1,5-isomers of compounds 3 and 4 were
done experimentally by the aromatic solvent induced shifts (ASIS)5,10 and a
two-dimensional correlation spectrum HMBC (Heteronuclear Multiple Bond

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3-METHYLISOXAZOLE-5-CARBOXAMIDES
427
Scheme.
Correlation).11,12 In the ASIS experiment, the 1H NMR spectra are recorded
1
in chloroform-d1 and benzene-d6 as solvents and all H signals were shifted
to upfield in benzene-d6 when compared with the initial positions in
chloroform-d1. Due to the anisotropy solvatation9,5 of the aromatic solvent,
the hydrogens closer to N-1 (an amidic nitrogen, with partial positive
charge) experience more shielding than the others hydrogens of the mole-
cule. Then we observed that R5 (hydrogen or alkyl groups) in compounds
3a–c and 4a–c was shifted upfield more in one isomer than in the other.

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MARTINS ET AL.
Thus, it was possible to assign the isomer that resonates more upfield as the
1,3-isomer (R5 is closer to N-1). The assignment proposed were confirmed
with the HMBC method. In the HMBC experiment, the long range coupling
constant (2,3JC-H) was optimized for 7 Hz. The experiment showed that the
carbonyl carbon (attached on N-1) presented a cross-peak with the hydro-
gen attached on C-5 (R5 ¼ H) for compounds 3a and 4a which were used as
standard compounds. This fact identified the 1,3-isomers, where R5 ¼ H is
three bonds from the N-1 carbonyl carbon.
EXPERIMENTAL
Unless otherwise indicated all common reagents and solvents were
used as obtained from commercial suppliers without further purification.
Yields listed in Table 1 are of isolated compounds and all melting points
were taken on a melting point microscope Reichert-Thermovar. Elemental
analysis was carried out on an Elemental Analysensysteme Vario EL equip-
1
ment. H and 13C NMR spectra were recorded on a Bruker DPX 400, at
298 K, digital resolution of Æ 0.01 ppm, 0.5 M in chloroform-d1/TMS.
Synthesis of 3-Methylisoxazole-5-carboxamides 2a–f
General Procedure
A mixture of 1 (10 mmol), with catalytic amounts of pyridine, and
thionyl chloride (1.43 g, 12 mmol) was refluxed for 12–16 h. The mixture
was cooled to room temperature, the amine (R1R2NH, 12 mmol) added
slowly, and the mixture stirred for 8–12 h at 60ꢀC. The crude product was
washed with water and then diluted in chloroform. The solvent was eva-
porated and the products 2a–f were recrystallized from a mixture of
hexane/ethyl acetate. Yields and selected physical and spectroscopic data
are presented in Tables 1 and 2.
Synthesis of 5-[(1H-Pyrazol-1-yl)carbonyl]-
3-methylisoxazoles 3a–d and 4a–d
General Procedure
A mixture of 1 (10 mmol), with catalytic amounts of pyridine, and
thionyl chloride (1.43 g, 12 mmol) was refluxed for 12–16 h. The mixture

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3-METHYLISOXAZOLE-5-CARBOXAMIDES
429
Table 1. Selected Physical and Elemental Analysis Data of Compounds 2a–f, 3a–d
and 4a–d
Elemental Analysis
(%)
Calcd./Found
Molecular
Formula
(M. wt.)
Isomer
Ratio
Yield
1, 3 : 1, 5a (%)b
M.P.
(ꢀC)
Compound
C
H
2a
C11H10N2O2
(202.21)
C12H12N2O2
(216.23)
C10H16N2O2
(196.24)
C9H9N3O3
(207.18)
C12H12N2O2
(216.23)
C10H16N2O2
(196.24)
C11H11N3O4
(249.21)
C12H13N3O4
(263.24)
C13H15N3O4
(277.26)
C17H15N3O4
(325.31)
C9H6F3N3O2
(245.15)
C10H8F3N3O2
(259.18)
C11H10F3N3O2
(273.21)
C15H10F3N3O2
(321.25)
–
95
88
72
78
88
55
73
72
70
62
82
80
78
78
155–156
148–150
140–141
149–153
158–160
164–166
122–124
84–85
65.34
65.16
66.66
66.60
61.21
61.04
52.18
51.90
66.66
66.43
61.21
61.00
53.02
52.82
54.75
54.55
56.32
56.10
62.77
62.53
44.092.47
43.95
4.98
4.97
5.59
5.58
8.22
8.20
4.38
4.35
5.59
5.57
8.22
8.19
4.45
4.40
4.98
4.95
5.45
5.43
4.65
4.63
2b
2c
2d
2e
2f
–
–
–
–
–
3a
3b
3c
3d
4a
4b
4c
4d
4 : 1
2 : 3
4 : 5
3 : 5
2 : 1
4 : 1
3 : 1
5 : 1
98–99
111–113
102–103
108–10946.34
148–150
99–100
2.46
3.11
46.19
48.36
48.20
56.08
55.90
3.09
3.69
3.67
3.14
3.13
1
b
aIsomer ratio obtained from H NMR data. Yields of isolated products.
was cooled to room temperature, the pyrazole (10 mmol) in chloroform
(5 mL) added slowly, and the mixture stirred for 8–12 h reflux. The crude
product was washed with water and then diluted in chloroform. The solvent
was evaporated and the products 2a–f were recrystallized from a mixture of

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MARTINS ET AL.
1
Table 2. Selected H and 13C NMR Dataa of Compounds 2a–f, 3, 4a–d
1
Compound
d H
d
13C, J (Hz)
2a
8.29(NH, s), 6.85 (H4, s), 2.38
(H6, s), 7.67–7.22 (H phenyl)
161.2 (C3), 108.4 (C4), 153.7 (C5),
11.4 (C6), 163.0 (C7), 136.6–121.2
(C phenyl).
2b
2c
9.48 (NH, s), 6.90 (H4, s), 2.35 160.5 (C3), 107.0 (C4), 155.8
(H6, s), 4.38 (CH2, s), 7.41–7.22 (C5), 11.0 (C6), 163.0 (C7), 138.7–
(H phenyl)
126.9(C phenyl), 42.2 (CH ).
2
6.30 (NH, s), 6.70 (H4, s), 2.35 160.9(C3), 107.3 (C4), 155.3 (C5),
(H6, s), 1.82 (CH2, q), 1.43 11.4 (C6), 163.8 (C7), 55.1 (CH28),
(2CH3, s), 0.90 (CH3, t)
32.9(CH2)9, 26.3 (CH210), 8.3
(CH311).
2d
3.50 (NH, s), 7.25 (H4, s), 2.35 160.6 (C3), 108.4 (C4), 154.1
(H6, s), 6.69(H4, s), 2.52 (Me5, s) (C5), 11.1 (C6), 161.5 (C7), 169.9
(C8), 97.0 (C9), 157.5 (C10), 12.1
(Me11).
7.20 (H4, s), 2.20 (H6, s), 3.45 159.0 (C3), 108.2 (C4), 157.5 (C5),
2e
2f
(Me, s), 7.40–7.22 (H phenyl)
11.0 (C6), 162.7 (C7), 142.6–126.7
(C phenyl).
9.48; 6.79 (H4, s), 6.74 (H40, s), 160.5 (C3), 160.7 (C30), 107.3 (C4),
2.31 (H6, s), 2.30 (H60, s), 3.07 106.9(C40),157.8(C5),157.7(C50),
(Me, s), 2.98 (Me0, s), 3.44 (CH2, 10.8 (C6), 163.3 (C7), 35.8 (Me),
t), 3.37 (CH20, t), 1.31 (CH2, qui), 33.0 (Me0), 49.5 (C8), 47.0 (C80),
1.20 (CH20, qui), 1.55 (CH2, sex), 29.9 (CH2), 28.3 (CH20), 19.4
0.90 (CH3, t)
(2CH3), 19.0 (2CH20), 13.6 (CH3),
13.4 (CH30).
3a
3b
7.67 (H4, s), 2.47 (H6, s), 2.40 160.8 (C3), 115.6 (C4), 158.0
(H60, s), 8.47 (H10, s), 7.60 (H100, (C5), 159.4 (C50), 11.5 (C6), 160.4
s), 7.01 (H11, s), 6.90 (H110, s), (C7), 159.4 (C70), 149.0 (C10),
4.47 (H15, s), 4.45 (H150, s), 1.45 153.5 (C100), 111.6 (C11), 108.0
(H16, s)
(C110), 131.2 (C12), 132.5 (C120),
161.0 (C13), 161.5 (C130), 61.8
(C15), 61.0 (C150), 14.2 (C16).
7.51 (H4, s), 2.43 (H6, s), 2.39 160.7 (C3), 115.1 (C4), 155.4
(H60, s), 2.70 (Me, s), 6.71 (H11, (C5), 11.2 (C6), 159.4 (C7), 158.8
s), 6.60 (H110, s), 4.43 (H15, s), (C70), 14.0 (Me), 147.0 (C10),
4.35 (H150, s), 1.41 (H16, s), 1.30 146.4 (C100), 111.6 (C11), 107.4
0
(H160, s)
(C110), 140.9(C12), 143.0 (C12 ),
161.0 (C13), 161.2 (C130), 61.5
(C15), 61.0 (C150), 14.1 (C16).
(continued )

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3-METHYLISOXAZOLE-5-CARBOXAMIDES
431
Table 2. Continued
1
Compound
d H
d
13C, J (Hz)
3c
7.53 (H4, s), 2.44 (H6, s), 2.38
(H60, s), 3.71 (CH2, q), 1.40
(CH3, t), 6.75 (H11, s), 6.60
(H110, s), 4.43 (H15, s), 4.35
(H150, s), 1.41 (H16, s), 1.30
(H160, s)
161.7 (C3), 115.0 (C4), 156.8
(C5), 11.3 (C6), 159.5 (C7),
19.2 (CH2), 13.1 (CH3), 149.0
(C10), 105.8 (C11), 141.3
(C12), 160.3 (C13), 60.9
(C15), 14.1 (C16).
3d
4a
4b
4c
7.67 (H4, s), 2.40 (H6, s), 2.30
(H60, s), 7.76–7.40 (H phenyl),
7.20 (H11, s), 7.03 (H110, s), 4.39
(H15, s), 4.31 (H150, s), 1.36 (H16,
s), 1.32 (H160, s)
160.0 (C3), 110.3 (C4), 159.4
(C5), 11.4 (C6), 160.0 (C7),
129.1–126.0 (C phenyl), 148.0
(C10), 105 (C11), 140.0 (C12),
160.0 (C13), 61.4 (C15), 13.9
(C16).
7.60 (H4, s), 2.49(H6, s), 2.37
(H60, s), 8.53 (H10, s), 7.76
(H100, s), 6.83 (H11, s), 6.70
(H110, s)
160.1 (C3), 115.6 (C4), 153.1
(C5), 11.4 (C6), 157.7 (C7),
131.8 (C10), 130.5 (C100),
104.4 (C11), 108.0 (C110),
147.0 (C12 J ¼ 39.3), 120.0
(C13 J ¼ 270.1).
7.43 (H4, s), 2.45 (H6, s), 2.34
(H60, s), 2.73 (Me, s)
160.6 (C3), 115.1 (C4), 155.2
(C5), 11.4 (C6), 159.3 (C7),
14.3 (Me), 147.2 (C10), 143.0
(C100), 108.1 (C11), 102.9
(C110), 146.0 (C12 J ¼ 39.1),
118.0 (C13).
7.43 (H4, s), 2.45 (H6, s), 2.47
(H60, s), 3.16 (CH2, q), 2.75
(CH20, q), 1.35 (CH3, t), 1.32
(CH30, t)
160.8 (C3), 115.0 (C4), 155.1
(C5), 11.3 (C6), 158.8 (C7),
21.6 (CH2), 18.6 (CH20), 11.9
(CH3), 12.7 (CH30), 153.6
(C10), 148.1 (C100), 106.3
(C11), 104.3 (C110), 145.0
(C12 J ¼ 39.0), 118.0 (C13
J ¼ 270.0).
4d
7.54 (H4, s), 2.46 (H6, s), 2.34
(H60, s), 7.06 (H11, s), 6.97
(H110, s), 7.85–7.54 (H phenyl)
162.0 (C3), 116.0 (C4), 155.5
(C5), 11.5 (C6), 159.7 (C7),
131.2–127.6 (C phenyl), 154.0
(C10), 113.8 (C11), 136.3
(C12), 120.0 (C13).
a 1H and 13C NMR spectra were recorded on a Bruker DPX 400, at 298 K, 0.5 M in
chloroform-d1/TMS. For compound 2f the data labeled as (0) refers to E-isomer (R2
is syn to carbonyl oxygen in the carboxamide group) and for 3, 4 the data refers to
1,5-isomer (see scheme).

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MARTINS ET AL.
hexane/ethyl acetate. Yields and selected physical and spectroscopic data are
presented in Tables 1 and 2.
ACKNOWLEDGMENTS
The authors thank the Conselho Nacional de Desenvolvimento
Cientıfico e Tecnologico (CNPq/PADCT), Fundacao de Amparo a Pesquisa
do Estado do Rio Grande do Sul (FAPERGS) for financial support. The
fellowhips from CNPq, CAPES and FAPERGS are also acknowledged.
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Received in the USA March 19, 2001

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