790
Z. Yang, J. Wang, L. Li, C. Ye, and H. Liu
Vol 46
recorded as indicated on a Varian INOVA600 spectrometer
operating at 600 MHz for 1H nuclei and 150 MHz for 13C
nuclei. Chemical shifts are reported downfield from TMS, and
coupling constants are given in hertz. Mass spectra were
obtained on Perkin Elmer Mass Spectrometer. The elemental
analysis was carried out using Flashea 1112Series CHNS-O
Analyzer and the METTLER TOLEDO MX5 (Max5.1 g d ¼
1 lg) weighting device. Quantitative analyses were carried out
over a Shimadzu LCꢂ20A HPLC (Column: Ultimate XB-C18
150 ꢃ 4.6 mm, 5 lm).
85% ethanol were heated to boiling on an oil bath, the stirrer
was started, and a solution of 75 mL concentrated hydrochloric
acid in 300 mL 85% ethanol was added dropwise. The mixture
was refluxed for 5 h beyond the final addition of hydrochloric
acid, and then the hot mixture was made just alkaline to pH
paper by the addition of potassium hydroxide pellets. Without
allowing the mixture to cool, the iron was removed by filtra-
tion and the hot ethanol was used to wash the iron residue.
Hydrochloric acid (15%) was added until the filtrate was 4–5
to pH paper, and then the mixture was chilled to 0ꢀC for 12 h.
The resulting precipitate was filtered, washed with water, and
dried for about 24 h under vacuum with slight nitrogen flow at
80ꢀC to give 75 g (91.4%) of tan 5,6-diaminobenzimidazo-
lone-2 (3). The crude 3 was purified to afford 72 g (87.8%) of
light yellow pure 3. M.P.: > 300ꢀC; HPLC ꢁ 98%; IR:
Benzimidazolone-2 (1). Following a literature procedure,
a mixture of 54 g (0.5 mol) o-phenylenediamine, 34 g
(0.57 mol) urea, and 95 mL glycol were stirring under nitrogen
for 1 h at 130–140ꢀC, and then heated in an oil bath at a max-
imum temperature of 170ꢀC for 7 h [7]. The solution was
cooled down to 40–50ꢀC, and ꢄ35 mL of 95% ethanol were
added with stirring for 10 min, then ꢄ100 mL of water were
added. The precipitate was recovered by suction filtration and
slurried with successive batches of water and 95% ethanol.
The residue was dried at 100ꢀC to give 60.2 g of white benzi-
midazolone-2 (1). Yield 89.9%. M.P.: 317.7–318.6ꢀC; HPLC
3407.18, 3366.27, 3106.60, 1682.70, 850.39 cmꢂ1 1H NMR
;
(DMSO, 600 MHz): d 4.07 (s, 2H), 6.23 (s, 2H), 9.81(s, 2H);
13C NMR (DMSO, 150 MHz): d 96.910, 121.410, 129.550,
155.440; MS: 164. Anal. calc. for C7H8ON4: C 51.22, H 4.88,
N 34.15; found: C 50.40, H 5.67, N 33.44.
ꢁ 99%, IR: 3128.74, 3021.52, 1741.41, 1484.26, 736.67 cmꢂ1
;
Acknowledgments. The authors thank the Ningbo Natural Sci-
ence Fund (No. 2006 A610075) for financial support of this work.
The authors are also thankful for the financial support from the
Key Laboratory for the Synthesis and Application of Organic
Functional Molecules, Ministry of Education (No. 020-044114)
for this work.
1H NMR (DMSO, 600 MHz): d 6.87(s, 4H), 10.54 (s, 2H);
13C NMR (DMSO, 150 MHz): d 109.133, 121.060, 130.311,
155.934. Anal. calc. for C7H6ON2: C 62.69, H 4.48, N 20.90;
found: C 62.79, H 4.60, N 20.59.
5,6-Dinitrobenzimidazolone-2 (2). According to a variation
of the method of literature, 5,6-dinitrobenzimidazolone-2 was
prepared. Benzimidazolone-2 (67 g, 0.50 mol) was dissolved
in 450 g 98% sulfuric acid. The colorless solution was cooled
to 0–5ꢀC in an ice bath and 80 g (1.14 mol) of 90% fuming
nitric acid in 470 g 98% sulfuric acid was added dropwise to
the cooled, stirred solution. The reaction temperature was not
allowed to go above 5ꢀC during the addition. After the addi-
tion of the nitric acid was complete, the cold solution was
poured onto 3 kg of ice rapidly. The yellow precipitate was
collected via filtration and washed thoroughly four times with
1-L portions of cold water. After drying at 100ꢀC, 101.6 g yel-
low 5,6-dinitrobenzimidazolone-2 was obtained (HPLC 93%).
Yield 90.7%. The crude 2 was recrystallized from 60% aque-
ous acetone to afford 80 g pure 2. M.P. > 300ꢀC, HPLC ꢁ
97%, IR: 3289.9, 3073.67, 1721.95, 1629.54, 1537.29,
REFERENCES AND NOTES
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1
1332.22, 883.59 cmꢂ1; H NMR (DMSO, 600MHz): d 7.65 (s,
2H), 11.78 (s, 2H); 13C NMR (DMSO, 150 MHz): d 105.560,
133.255, 137.810, 156.120; MS: 224. Anal. calc. for
C7H4O5N4: C 37.50, H 1.79, N 35.71; found: C 37.65, H 2.00,
N 35.62.
5,6-Diaminobenzimidazolone-2 (3). A mixture of 112 g
(0.5 mol) of crude 2, 224 g (4 mol) of iron dust, and 1.2 L of
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Journal of Heterocyclic Chemistry
DOI 10.1002/jhet