The Journal of Organic Chemistry
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compound-appropriate mixtures of hexanes and EtOAc as eluent.
Thin-layer chromatography was performed on precoated silica gel
with those of the product previously isolated from the acid-catalyzed
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reaction of 2 with mesitylene as a white solid, mp 134−136 °C: H
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plates and visualized by ultraviolet light and/or I2 vapor. H and 13C
NMR (CDCl3) δ 2.13 (s, 6H), 2.28 (s, 3H), 3.06 (s, 3H), 6.89 (s, 2H),
9.49 (br s, 1H); 13C NMR (CDCl3) δ 154.8, 151.3, 140.2, 137.9,
129.5, 129.3, 25.3, 21.1, 17.6.
NMR spectra were obtained on a 400 MHz NMR spectrometer.
Chemical shifts are reported in units of parts per million downfield
from TMS. Elemental analyses were performed by a commercial
laboratory. High-resolution mass spectral analysis was performed via
GC-MS (TOF EI). N-Methyl-1,3,5-triazolinedione (2) was synthe-
sized via oxidation of commercially obtained N-methylurazole with
N2O4 according to the literature and sublimed before use.34,35 All
other chemicals and solvents were obtained from commercial sources
and used without further purification.
General Procedure: Photochemical Reactions of N-Methyl-
1,2,4-triazoline-3,5-dione (2) with Substituted Benzenes. A
solution of a substituted benzene (1.5 mmol) in 5 mL of CH2Cl2 was
transferred to the reaction vessel of the photochemical apparatus
described in General Methods. To this was added a solution of 2 (113
mg, 1 mmol) in 5 mL of CH2Cl2. The reaction vessel was sealed with a
stopper and cool water circulated within the apparatus. Irradiation with
three 300 W incandescent bulbs, arranged within 1 cm of the outside
wall of the apparatus, was initiated and continued until the pinkish red
color of the reaction mixture was just bleached. The reaction mixture
was transferred to a 25 mL RBF, the solvent removed in vacuo, and
the reaction mixture subjected to column chromatography.
The 1H and 13C NMR signals in the crude spectra corresponding to
13b matched those of an independently synthesized compound (see
below).
1-(2,4,5-Trimethylbenzyl)-4-methyl-1,2,4-triazoline-3,5-dione
(14). Upon completion of reaction with 1,2,4,5-tetramethylbenzene
(0.201 g) after 8 h, column chromatography afforded 0.141 g (57%
yield) of 14 as a white solid, mp 175−176 °C: IR (cm−1) 3198 (N−
H), 2992, 1779, 1676; 1H NMR (CDCl3) δ 2.19 (s, 6H), 2.27 (s, 3H),
3.02 (s, 3H), 4.59 (s, 2H), 6.94 (s, 1H), 6.99 (s, 1H), 8.00 (br s, 1H);
13C NMR (CDCl3) δ 155.0, 154.0, 137.1, 134.4, 134.3, 132.2, 131.1,
129.1, 48.4, 25.2, 19.3, 19.2, 18.4. Anal. Calcd for C13H17N3O2: C,
63.12; H, 6.93; N, 17.00. Found: C, 62.86; H, 7.08; N, 16.73.
Benzylic Substituted Products from Reaction with Pentamethyl-
benzene (15a−c). Upon completion of reaction with pentamethyl-
benzene (0.224 g) after 5 h, column chromatography afforded 0.1064
g (41% yield) of an inseparable mixture of urazoles 15a−c as a white
solid. Using the signal integrations from the 1H NMR spectrum of the
crude mixture (provided in the Supporting Information), the spectra
for each of the individual isomers could be determined. Minor isomer
15c: 1H NMR (CDCl3) δ 2.21 (s, 6H), 2.24 (s, 6H), 2.99 (s, 3H), 4.75
(s, 2H), 6.93 (s, 1H), 8.05 (br s, 1H). The other two regioisomers,
15a,b could not be clearly differentiated. However, one was present in
1-(2,4,6-Trimethoxybenzene)-4-methyl-1,2,4-triazoline-3,5-dione
(9).3 Upon completion of reaction with 1,3,5-trimethoxybenzene
(0.252 g) after 0.5 h, the solvent was removed and the residue
recrystallized directly from EtOH to afford 0.244 g (87% yield) of 9 as
colorless crystals, mp 252−253 °C: IR (cm−1) 3152 (N−H), 3041,
2986, 1767, 1688, 1131; 1H NMR (DMSO-d6) δ 2.94 (s, 3H), 3.75 (s,
6H), 3.82 (s, 3H), 6.30 (s, 2H), 10.68 (br s, 1H); 13C NMR (DMSO-
d6) δ 162.1, 158.7, 153.5, 152.7, 105.4, 91.1, 56.1, 55.7, 24.7.
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greater amount than the other. Major isomer: H NMR (CDCl3) δ
2.14 (s, 3H), 2.22 (s, 3H), 2.27 (s, 3H), 2.31 (s, 3H), 2.99 (s, 3H),
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4.70 (s, 2H), 6.83 (s, 1H), 8.05 (br s, 1H). Remaining isomer: H
NMR (CDCl3) δ 2.17 (s, 3H), 2.19 (s, 3H), 2.23 (s, 3H), 2.24 (s, 3H),
2.97 (s, 3H), 4.61 (s, 2H), 8.05 (br s, 1H). Elemental analysis was
conducted on the mixture of isomers. Anal. Calcd for C14H19N3O2: C,
64.33; H, 7.33; N, 16.09. Found: C, 64.34; H, 7.45; N, 15.94.
1-(2,3,4,5,6-Pentamethylbenzyl)-4-methyl-1,2,4-triazoline-3,5-
dione (16). Upon completion of reaction with hexamethylbenzene
(0.243 g) after 8 h, column chromatography afforded 0.153 g (56%
1-(2,4-Dimethoxybenzene)-4-methyl-1,2,4-triazoline-3,5-dione
(10).3 Upon completion of reaction with 1,3-dimethoxybenzene
(0.202 g) after 3 h, column chromatography afforded 0.198 g (79%
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yield) of 10 as a white solid, mp 185−186 °C: H NMR (CDCl3) δ
3.15 (s, 3H), 3.82 (s, 3H), 3.85 (s, 3H), 6.49 (dd, J = 2.5, 8.5 Hz, 1H),
6.52 (d, J = 2.5 Hz, 1H), 7.41 (d, J = 8.5 Hz, 1H), 8.15 (br s, 1H); 13C
NMR (CDCl3) δ 161.1, 155.4, 154.9, 152.5, 127.9, 117.4, 104.6, 99.7,
55.9, 55.7, 25.3.
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yield) of 16 as a white solid, mp 237−239 °C: H NMR (CDCl3) δ
2.24 (s, 6H), 2.26 (s, 3H), 2.32 (s, 6H), 3.10 (s, 3H), 4.83 (s, 2H),
6.40 (br s, 1H); 13C NMR (CDCl3) δ 155.0, 154.0, 136.0, 133.7,
133.3, 126.5, 45.7, 25.2, 17.1, 16.8, 16.5. Anal. Calcd for C15H21N3O2:
C, 65.42; H, 7.69; N, 15.27. Found: C, 65.16; H, 7.83; N, 14.93.
1-(4-Methoxybenzyl)-4-methyl-1,2,4-triazoline-3,5-dione (17a)
and 1-(2-Methoxy-5-methylbenzyl)-4-methyl-1,2,4-triazoline-3,5-
dione (17b). Upon completion of reaction with 4-methylanisole
(0.183 g) after 24 h, column chromatography afforded 0.101 g (43%
yield) of a difficultly separable mixture of 17a,b in an 83:17 ratio,
respectively. When several such product mixtures were combined and
subjected to further column chromatography, it was possible to isolate
sufficient amounts of pure fractions of each compound for
characterization by combining very early (17b) and very late (17a)
fractions about the region where they nearly coelute. Compound 17a
1-(4-Methoxy-2-methylbenzene)-4-methyl-1,2,4-triazoline-3,5-
dione (11a).3 Upon completion of reaction with 3-methylanisole
(0.183 g) after 18 h, column chromatography afforded 0.186 g (79%
yield) of a mixture of regioisomeric 1-arylurazoles 11a−c as a foamy
white solid. The major product, 11a, exhibited spectral data identical
with those of the product previously isolated from the acid-catalyzed
reaction of 2 with 3-methoxytoluene: 1H NMR (DMSO-d6) δ 2.20 (s,
3H), 2.96 (s, 3H), 3.77 (s, 3H), 6.84 (dd, J = 3.1, 8.5 Hz, 1H), 6.90 (d,
J = 3.1 Hz, 1H), 7.26 (d, J = 8.5 Hz, 1H), 10.87 (br s, 1H); 13C NMR
(CDCl3) δ 160.0, 154.8, 152.2, 138.0, 128.1, 127.0, 116.2, 112.2, 55.5,
25.3, 18.0.
In addition to 11a (∼86% of the product mixture according to
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was isolated as a white solid, mp 147−148 °C: H NMR (CDCl3) δ
integration in the H NMR spectrum), the crude reaction mixture
3.03 (s, 3H), 3.79 (s, 3H), 4.59 (s, 2H), 6.86 (d, J = 8.5 Hz, 2H), 7.24
(d, J = 8.5 Hz, 2H), 8.1 (br s, 1H); 13C NMR (CDCl3) δ 159.8, 155.0,
154.4, 130.2, 126.0, 114.3, 55.3, 50.2, 25.2. Anal. Calcd for
C11H13N3O3: C, 56.15; H, 5.57; N, 17.87. Found: C, 55.83; H, 5.48;
N, 17.72. Compound 17b was isolated as a white solid, mp 147−148
°C: 1H NMR (CDCl3) δ 2.31 (s, 3H), 3.17 (s, 3H), 3.88 (s, 3H), 6.88
(d, J = 8.4 Hz, 1H), 7.11 (dd, J = 1.8, 8.4 Hz, 1H), 7.45 (d, J = 1.8 Hz,
1H), 8.3 (br s, 1H); 13C NMR (CDCl3) δ 154.6, 151.6, 150.9, 131.0,
129.6, 125.9, 123.9, 111.9, 56.0, 25.3, 20.5. Anal. Calcd for
C11H13N3O3: C, 56.15; H, 5.57; N, 17.87. Found: C, 55.73; H, 5.45;
N, 17.51.
1-(4-Methylbenzyl)-4-methyl-1,2,4-triazoline-3,5-dione (18a) and
1-(2,5-Dimethylbenzyl)-4-methyl-1,2,4-triazoline-3,5-dione (18b).
Upon completion of reaction with p-xylene (0.160 g) after 14 h,
column chromatography afforded 0.065 g (30% yield) of 18a as a
white solid, mp 149−150 °C: 1H NMR (CDCl3) δ 2.33 (s, 3H), 3.02
(s, 3H), 4.61 (s, 2H), 7.14 (d, J = 8.0 Hz, 2H), 7.19 (d, J = 8.0 Hz,
suggested two other regioisomeric products in a ratio of ∼1:1
tentatively assigned structures 11b,c (see text). The 1H NMR
spectrum of the crude mixture is provided in the Supporting
Information.
1-(2,4-Dimethoxy-6-methylbenzene)-4-methyl-1,2,4-triazoline-
3,5-dione (12).3 Upon completion of reaction with 3,5-dimethox-
ytoluene (0.228 g) after 1 h, column chromatography afforded 0.257 g
(97% yield) of 12 as a white solid, mp 165−166 °C: 1H NMR
(CDCl3) δ 2.25 (s, 3H), 3.10 (s, 3H), 3.74 (s, 3H), 3.79 (s, 3H), 6.31
(d, J = 2.5 Hz, 1H), 6.35 (d, J = 2.5 Hz, 1H), 9.10 (br s, 1H); 13C
NMR (CDCl3) δ 161.5, 157.6, 155.4, 153.1, 140.8, 115.6, 106.4, 97.1,
55.9, 55.5, 25.3, 18.0.
1-(2,4,6-Trimethylbenzene)-4-methyl-1,2,4-triazoline-3,5-dione
(13a).3 Upon completion of reaction with mesitylene (0.180 g) after
10 h, column chromatography afforded 0.182 g (78% yield) of 13a,b as
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an inseparable mixture in a ratio (by H NMR integration) of 2.3:1,
respectively. The major product, 13a, exhibited spectral data identical
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dx.doi.org/10.1021/jo4001417 | J. Org. Chem. XXXX, XXX, XXX−XXX