Helvetica Chimica Acta ± Vol. 86 (2003)
2245
(
s, 3 H); 3.69 (s, 3 H); 3.87( s, 6 H); 5.96 (s, 2 H); 5.99 (s, 2 H); 7.28 (s, 1 H); 7.33 (s, 1 H). Anal. calc. for
10: C 57.42, H 4.34; found: C 57.48, H 4.30.
Methyl 7-Methoxy-6-nitro-1,3-benzodioxole-5-carboxylate (9). Conc. HNO
to a stirred suspension of 7 (10 g, 47.6 mmol) in 50 ml of Ac O over a period of 1 h at a temp. of 08. The mixture
20 18
C H O
3
(100 ml) was added dropwise
2
was stirred for an additional hour and then poured into ice-water. The precipitate was collected and
1
recrystallized from AcOEt to yield 11.2 g (91.8%) of 9. Yellowish needles. M.p.126 ± 1288. H-NMR (CDCl
3
):
3
.97( s, MeO); 4.17( s, MeOAr); 6.24 (s, OCH
found: C 47.10, H 3.53.
Methyl 6-Amino-7-methoxy-1,3-benzodioxole-5-carboxylate (10). A suspension of SnCl
0 ml of conc. HCl was heated until becoming a homogeneous soln. and cooled to 408. Then, 9 (5.0 g, 19.6 mmol)
was added. The mixture was refluxed for 30 min, cooled, neutralized with 10% aq. NaOH soln., and extracted
2
O); 7.24 (s, arom. H). Anal. calc. for C10
H
9
NO
7
: C 47.07, H 3.55;
2
2
¥ H O (5.0 g) in
5
with CHCl
3
. The usual workup provided 3.0 g (68%) of 10. Needles. M.p. 90 ± 918. IR: 3300 ± 3500s (ArNH
): 3.82 (s, MeO); 3.99 (s, MeOAr); 5.00 (br., ArNH , exchangeable with D O); 5.88
O); 7.01 (s, arom. H). Anal. calc. for C10 N: C 53.33, H 4.92; found: C 53.38, H 4.89.
Methyl 6-Bromo-7-methoxy-1,3-benzodioxole-5-carboxylate (11). CuSO (2.0 g) and KBr (1.0 g) were
dissolved in 10 ml of H O. The mixture was heated to 508, and a soln. of NaOH (0.6 g) and NaHSO (0.6 g) in
O (2 ml) was added. The mixture was stirred to afford CuBr. A suspension of CuBr in 40% HBr was prepared
for the next step. A suspension of 10 (1.0 g, 4.44 mmol) in 40% HBr (5 ml) was cooled to 0 ± 58, and a soln. of
NaNO (0.5 g, 7.2 mmol) in 15 ml of H O was added. The resulting diazonium salt was slowly added to the above
suspension of CuBr in 40% HBr. The mixture was stirred overnight at 58. The orange-red color faded gradually.
2
).
1
H-NMR (CDCl
s, OCH
3
2
2
(
2
11 5
H O
4
2
3
H
2
2
2
The mixture was heated to 50 ± 608 for 30 min, and was washed with H
2
O and 10% aq. NaHCO
3
soln. to yield
O);
1
0
.9 g (70%) of 11 as a solid. M.p. 82 ± 838: H-NMR (CDCl
3
): 3.91 (s, MeO); 4.04 (s, MeOAr); 6.07( s, OCH
2
7
.04 (s, arom. H). Anal. calc. for C10
9 5
H O Br: C 41.55, H 3.14; found: C 41.56, H 3.16.
Dimethyl 4,4'-Dimethoxy-[5,5']bi[1,3-benzodioxolyl]-6,6'-dicarboxylate (2). A mixture of 11 (1.0 g,
3
.46 mmol), activated Cu powder (1.0 g), and anh. DMF (5 ml) was refluxed for 4 h under vigorous stirring.
The mixture was filtered, and the filtrate was concentrated. The resulting residue was purified by FC (Al
2
O
3
;
1
hexanes ! hexanes/CHCl
.56 (s, 2 MeO); 3.74 (s, 2 MeOAr); 6.16 (s, 2 OCH
H 4.34; found: C 57.45, H 4.35.
3
) to afford 375 mg (52%) of 2 as a solid. M.p. 207± 208 8. H-NMR ((D
6
)-acetone):
10: C 57.42,
3
2
O); 7.16 (s, 2 arom. H). Anal. calc. for C20
H
18
O
The authors are grateful to Dr. Haoyun An for help with the preparation of this manuscript. J. C. is grateful
for financial support from the National Natural Science Foundation of China (29972009). K. Z. thanks for the
NSFC (#30125043) for the Outstanding Young Scholarship of and the Cheung Kong Scholars Programme of the
Ministry of Education, PRC.
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