Generation of Unstable Mesoionic 1,3-Dioxolium-4-olates
N-Anisoyl-N,N′-bis(methoxycarbonyl)-p-nitrobenzamidine (13d)
was isolated in a yield of 92% in the reaction of 6b with 12b.
N-p-Chlorobenzoyl-N,N′-bis(ethoxycarbonyl)-p-nitrobenzami-
Calcd for C15H12N2O4: C, 63.38; H, 4.25; N, 9.85. Found: C, 63.41;
H, 4.34; N, 9.90.
N-Acetyl-N-p-cyanophenyl-p-nitrobenzamide (21f) (95%):
1
1
dine (13g) (70%): white powders; mp 90.5-91.0 °C; H NMR
pale green cube; mp 150-152 °C; H NMR (CDCl3) δ 8.20 (d, 2
(CDCl3) δ 8.31 (d, 2 H, J ) 8.9 Hz), 8.00 (d, 2 H, J ) 8.4 Hz),
7.70 (d, 2 H, J ) 8.4 Hz), 7.46 (d, 2 H, J ) 8.7 Hz), 4.18 (q, 2 H,
J ) 6.9 Hz), 4.12 (d, 2 H, J ) 7.1 Hz), 1.19 (t, 3 H, J ) 7.1 Hz),
1.03 (t, 3 H, J ) 7.1 Hz); IR (KBr) 1744, 1593, 1523, 1348, 1252,
1091, 1011 cm-1. Anal. Calcd for C20H18ClN3O7: C, 53.64; H,
4.05; N, 9.38. Found: C, 53.47; H, 3.88; N, 9.30.
H, J ) 8.6 Hz), 7.70 (d, 4 H, J ) 8.6 Hz), 7.30 (d, 2 H, J ) 8.6
Hz), 2.45 (s, 3 H); IR (KBr) 2229, 1691, 1604, 1520, 1349, 1309,
1245 cm-1. Anal. Calcd for C16H11N3O4: C, 62.14; H, 3.58; N,
13.59. Found: C, 62.27; H, 3.70; N, 13.61.
N-p-Anisoyl-N-phenyl-p-nitrobenzamide (21c) was isolated in
a yield of 84% in the reaction of 6b with 17a.
N-p-Chlorobenzoyl-N,N′-bis(methoxycarbonyl)-p-nitrobenza-
midine (13h) (45%): white needles; 140.0-140.5 °C; δ 8.31 (d,
2 H, J ) 9.1 Hz), 7.99 (d, 2 H, J ) 8.6 Hz), 7.70 (d, 2 H, J ) 8.7
Hz), 7.47 (d, 2 H, J ) 8.9 Hz), 3.75 (s, 3H), 3.69 (s, 3H); IR (KBr)
1747, 1593, 1523, 1348, 1253, 1090, 1012, 853, 752 cm-1. Anal.
Calcd for C18H14ClN3O7: C, 51.50; H, 3.36; N, 10.01. Found: C,
51.60; H, 3.32; N, 9.96.
N-p-Anisoyl-N-p-cyanophenyl-p-nitrobenzamide (21d) was
isolated in a yield of 95% in the reaction of 6b with 17b.
N-p-Chlorobenzoyl-N-phenyl-p-nitrobenzamide (21g) (81%):
1
white cubes; mp 163-164 °C; H NMR (CDCl3) δ 8.23 (d, 2 H,
J ) 8.9 Hz), 7.86 (d, 4 H, J ) 8.9 Hz), 7.67 (d, 2 H, J ) 8.6 Hz),
7.42-7.36 (m, 3 H), 7.34 (d, 2 H, J ) 8.6 Hz), 7.17-7.14 (m, 2
H); IR (KBr) 1715, 1667, 1591, 1525, 1352, 1267, 849 cm-1. Anal.
Calcd for C20H13ClN2O4: C, 63.08; H, 3.44; N, 7.36. Found: C,
63.00; H, 3.54; N, 7.48.
General Procedure for Dehydrochlorination of R-Acyloxyar-
yl-
acetyl Chloride in the Presence of Nitrosobenzenes. A benzene
solution (5 mL) of diisopropylethylamine (0.55 mmol) was added
to a benzene solution (5 mL) of R-acyloxyarylacetyl chlorides 11a
or 11b (0.5 mmol) and nitrosobenzene 20a or p-nitrosobenzene
20b at room temperature and the resultant solution was stirred
overnight. The reaction mixture was washed with water, dilute
hydrochloric acid, and water and then dried over magnesium sulfate.
The resultant solution was chromatographed over silica gel with
toluene as an eluent, giving white solids. The solids were recrystal-
lized from CH2Cl2/ether/pentane.
N-p-Chlorobenzoyl-N-p-cyanophenyl-p-nitrobenzamide (21h)
(60%): white crystals; mp 113-114 °C; 1H NMR (CDCl3) δ 8.25
(d, 2 H, J ) 9.1 Hz), 7.85 (d, 4 H, J ) 8.9 Hz), 7.69 (d, 2 H, J )
8.7 Hz), 7.64 (d, 2 H, J ) 8.7 Hz), 7.37 (d, 2 H, J ) 8.7 Hz), 7.27
(d, 2 H, J ) 9.1 Hz); IR (KBr) 2232, 1692, 1525, 1603, 1505,
1401, 1291, 1261, 1230, 848 cm-1; HRMS (EI+) calcd for C21H12-
ClN3O4 M+ 405.0516, found M+ 405.0511.
Reaction of 1,3-Dioxolium-4-olate 5b with Singlet Oxygen.
A benzene solution (5 mL) of 6b (0.5 mmol) was added dropwise
over 1 h to a benzene solution (10 mL) of Rh2(OAc)4 (0.5 mg) and
9,10-diphenylanthracene (2 mg) at 30 °C under irradiation of
tungsten lamp while oxygen was bubbling through the mixture and
stirred until the light red solution turned clear. After the solvent
was distilled off, the NMR spectrum of the reaction mixture showed
the presence of p-anisic p-nitrobenzoylformic anhydride 28b and
p-anisic p-nitrobenzoic anhydride 27b in a ratio of ca. 5:4. The
mixture was dissolved in absolute methanol and left at room
temperature overnight. After methanol was removed, the residue
was dissolved in ether and the ether solution was washed with an
aqueous sodium bicarbonate solution. The NMR spectrum of the
ethereal extract showed methyl p-nitrobenzoylformate 29 (41%)
and methyl p-nitrobenzoate 30 (35%) in a ratio of ca. 1:0.85.
p-Anisic acid 31 (89%) was obtained by acidification of aqueous
solution. Methyl p-nitrobenzoylformate 29 and methyl p-nitroben-
zoate 30 proved identical with independently synthesized authentic
samples.
N-Acetyl-N-phenylbenzamide (21a) (84%): white needles; mp
1
64-65 °C; H NMR (CDCl3) δ 7.63-7.59 (m, 2 H), 7.41-7.25
(m, 6 H), 7.17-7.14 (m, 2 H), 2.44 (s, 3 H); IR (KBr) 3060, 3013,
1694, 1598, 1489, 1371, 1263, 1210, 1127, 1079, 1015, 923, 894,
793, 758 cm-1. Anal. Calcd for C15H13NO2: C, 75.30; H, 5.48; N,
5.85. Found: C, 75.16; H, 5.59; N, 5.85.
N-Acetyl-N-p-cyanophenylbenzamide (21b) (67%): white pow-
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der; mp 118-119 °C; H NMR (CDCl3) δ 7.61 (d, 2 H, J ) 8.9
Hz), 7.58-7.55 (m, 2 H), 7.48-7.42 (m, 1 H), 7.36-7.30 (m, 2
H), 7.24 (d, 2 H, J ) 8.9 Hz), 2.51 (s, 3 H); IR (KBr) 2233, 1693,
1603, 1367, 1282, 1259, 1204, 832 cm-1. Anal. Calcd for
C16H12N2O2: C, 72.72; H, 4.58; N, 10.60. Found: C, 72.68; H,
4.67; N, 10.55.
N-p-Anisoyl-N-phenyl-p-nitrobenzamide (21c) (61%): mp
132-133 °C; 1H NMR (CDCl3) δ 8.19 (d, 2 H, J ) 8.9 Hz), 7.85
(d, 2 H, J ) 8.9 Hz), 7.72 (d, 2 H, J ) 8.9 Hz), 7.40-7.16 (m, 5
H), 6.82 (d, 2 H, J ) 8.9 Hz), 3.80 (s, 3 H); IR (KBr) 1697, 1682,
1602, 1523, 1349, 1287, 1259, 1166, 1025, 849 cm-1. Anal. Calcd
for C21H16N2O5: C, 67.02; H, 4.28; N, 7.44. Found: C, 67.35; H,
4.53; N, 7.39.
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28b: H NMR (CDCl3) δ 8.39 (d, 2 H, J ) 8.9 Hz), 8.26 (d, 2
H, J ) 9.0 Hz), 8.06 (d, 2 H, J ) 9.0 Hz), 7.00 (d, 2 H, J ) 8.9
Hz), 3.91 (s, 3H).
Preparation of p-Anisic p-Nitrobenzoic Anhydride 27b. A
CH2Cl2 solution (3 mL) of anisoyl chloride (0.43 g) was added
dropwise to a CH2Cl2 solution (6 mL) of p-nitrobenzoic acid (0.42
g) and triethylamine (0.25 g) at 0 °C with stirring. After the solution
had been stirred for 1 h, p-anisic p-nitrobenzoic anhydride 27b
(0.054 g) deposited as white solids. The CH2Cl2 solution was
washed with dilute hydrochloric acid, aqueous sodium bicarbonate,
and water and then dried over anhydrous MagSO4. After evapora-
tion of the solvent, the residue and the white solids were conbined
and recrystallized with CH2Cl2/ether to give 27b as light yellowish
plates (0.61 g, 81%). p-Anisic p-nitrobenzoic anhydride 27b: mp
157-158 °C; 1H NMR (CDCl3) δ 8.38 (d, 2 H, J ) 9.2 Hz), 8.33
(d, 2 H, J ) 9.2 Hz), 8.09 (d, 2 H, J ) 8.9 Hz), 7.01 (d, 2 H, J )
8.9 Hz), 3.92 (s, 3H); IR (KBr) 1785, 1720, 1605, 1521, 1346,
1234, 1166, 1080 cm-1. Anal. Calcd for C15H11NO6: C, 59.80; H,
3.68; N, 4.65. Found: C, 59.60; H, 3.68; N, 4.70.
N-p-Anisoyl-N-p-cyanophenyl-p-nitrobenzamide (21d) (52%):
1
mp 256-258 °C; H NMR (CDCl3) δ 8.24 (d, 2 H, J ) 8.9 Hz),
7.85 (d, 2 H, J ) 8.9 Hz), 7.69 (d, 2 H, J ) 8.9 Hz), 7.68 (d, 2H,
J ) 8.9 Hz), 7.30 (d, 2 H, J ) 8.9 Hz), 6.85 (d, 2 H, J ) 8.9 Hz),
3.84 (s, 3 H); IR (KBr) 2231, 1683, 1603, 1525, 1349, 1256, 1169,
1110, 1025, 846 cm-1; HRMS (EI+) calcd for C22H15N3O5 M+
401.1012, found M+ 401.1006.
General Procedure for Rh2(OAc)4-Catalyzed Reaction of
Aryldiazoacetic Anhydrides 6a-c in the Presence of Ni-
trosobenzenes 20. A benzene solution (5 mL) of arydiazoacetic
anhydrides 6 (0.5 mmol), nitrosobenzenes 17 (0.55 mmol), and a
catalytic amount of Rh2(OAc)4 was stirred at 50 °C for 2 h. The
reaction mixture was chromatographed over silica gel with toluene
as an eluent, giving white solids. The solids were recrystallized
from CH2Cl2/ether/pentane.
N-Acetyl-N-phenyl-p-nitrobenzamide (21e) (84%): white
needles; mp 143-145 °C; H NMR (CDCl3) δ 8.18 (d, 2 H, J )
8.9 Hz), 7.71 (d, 4 H, J ) 8.9 Hz), 7.44-7.36 (m, 3 H), 7.20-
7.16 (m, 2 H), 2.39 (s, 3 H); IR (KBr) 3112, 1716, 1696, 1602,
1518, 1368, 1351, 1304, 1245, 1093, 1035, 860, 838 cm-1. Anal.
General Procedure of Dehydrochlorination of R-Acyloxyaryl-
acetyl Chloride in the Presence of Dimethyl Acetylenedicar-
boxylate (DMAD). A benzene solution of 1.1 equiv of i-Pr2NEt
was added dropwise to a benzene solution of R-acyloxyphenylacetyl
chloride 11 and 2 equiv of DMAD and stirred for 2 h at room
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J. Org. Chem, Vol. 72, No. 4, 2007 1333