Molecules 2005, 10
1405
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1581 cm-1 (C=N), 1036 (N-O); H-NMR (CDCl3) δ: 13.01 (br s, 1H, -OH), 7.25-7.94 (m, 10H,
13
aromatics), C-NMR (CDCl3) δ: 155.9, 154.8, 145.9, 135.8, 128.6, 127.4, 125.1, 123.6, 110.4. Anal.
Calcd. For C17H11NO3: C 73.64, H 4.00, N 5.05. Found: C 73.55, H 4.06, N 5.11.
General procedure for the synthesis of oxime-ethers 5a-h.
Compound 4 (1.0 g, 3.6 mmol), K2CO3 (0.55 g, 4 mmol) and an appropriate alkyl halogenide or
acid chloride (3.6 mmol) were mixed in absolute acetone. The mixture was refluxed to complete the
reaction while monitoring its course by IR. After cooling to room temperature, the mixture was poured
into water. The solid thus separated was filtered off, washed with copious water and recrystallized
from ethanol.
Bisbenzofuran-2-yl-methanone O-methyl oxime (5a). Yield: 0.43 g (41.03 %); m.p.: 131.0 ˚C; IR
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(KBr): 2937 cm-1 (-CH3 aliphatics), 1613 cm-1 (C=N); H-NMR (CDCl3) δ: 4.30 (s, 3H, -CH3), 7.18-
7.77 (m, 10H, aromatics). 13C-NMR (CDCl3) δ: 156.9, 155.7, 148.3, 141.0, 130.2, 128.5, 127.8, 123.9,
113.8, 54.4. Anal. Calcd. For C18H13NO3: C 74.22, H 4.50, N 4.81. Found: C 73.89, H 4.61, N 5.02.
Bisbenzofuran-2-yl-methanone O-benzyl oxime (5b). Yield: 1.87 g (70.56 %); m.p.: 127.6 ˚C; IR
(KBr): 2936 cm-1 (-CH3, aliphatics), 1614 cm-1 (C=N), 1004 (N-O); 1H-NMR (CDCl3) δ: 5.56 (s, 2H, -
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CH2-), 7.26-7.76 (m, 10H, aromatics). C-NMR (CDCl3) δ: 156.9, 155.7, 150.9, 148.4, 138.8, 130.3,
129.8, 127.7, 125.2, 123.7, 113.6, 80.5. Anal. Calcd. For C24H17NO3: C 78.46, H 4.66, N 3.81. Found:
C 78.44, H 4.75, N 3.94.
Bisbenzofuran-2-yl-methanone O-oxiranylmethyl oxime (5c). Yield: 0.52 g (21.66 %); m.p.: 88.4 ˚C;
IR (KBr): 2930 cm-1 (-CH2-, aliphatics), 1613 cm-1 (C=N), 1259 cm-1 (C-O, on benzofuran ring), 1046
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δ
cm-1 (C-O, epoxide), 1014 (N-O); H-NMR (CDCl3): H , 2.76 (dd, 1H, jDC = 5.3 Hz, jDB = 2.6 Hz),
D
δ
δ
δ
H , 2.85 (dd, 1H, jCB = 4.8 Hz, jCD = 5.3 Hz), B, 3.47 (m, 1H, HB), H , 4.41 (dd, 1H, jAE = 12.2 Hz,
C
E
δ
jBE = 6.4 Hz), H , 4.77 (dd, 1H, jAB = 2.8 Hz, jAE = 12.2 Hz), ), 7.25-7.83 (m, 10H, aromatics).
13C-NMR (CDCl3) δ: 156.9, 155.8, 146.1, 130.1, 127.8, 125.2, 123.7, 113.7, 78.4, 52.1, 46.8. Anal.
A
Calcd. For C20H15NO4: C 72.06, H 4.54, N 4.20. Found: C 71.96, H 4.49, N 4.17.
HB HC
HA
X
X = Benzofuran-2-yl
C N
O
C
C
C
HE
X
HD
O
Bisbenzofuran-2-yl-methanone O-benzoyl oxime (5d). Yield: 1.29 g (94.16 %); m.p.: 154.9 ˚C; IR
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(KBr): 1747 cm-1 (C=O), 1612 cm-1 (C=N), 1057 (N-O); H-NMR (CDCl3) δ: 7.28-7.79 (m, 13H,
aromatics), 8.18-21 (m, 2H, aromatics); 13C-NMR (CDCl3) δ: 165.4, 157.7, 156.9, 149.8, 146.1, 132.0,
130.8, 129.4, 128.5, 125.9, 125.5, 124.6, 124.1, 113.9. Anal. Calcd. For C24H15NO4: C 75.58, H 3.96,
N 3.67. Found: C 75.43, H 4.02, N 3.88.
(Bis-benzofuran-2-yl-methyleneaminooxy)-acetic acetic acid ethyl ester (5e). Yield: 5.87 g (98.62 %);
m.p.: 116.7 ˚C; IR (KBr): 2977 cm-1 (aliphatics), 1755 cm-1 (C=O), 1614 cm-1 (C=N), 1033 cm-1 (N-
1
O), 1087 cm-1 (C-O); H-NMR (CDCl3) δ: 1.34 (t, 3H, j=7.21. –CH3), 4.31 (q, j=7.05, 2H, -CH2-),