M. D. H. Bhuiyan, K.-X. Zhu, P. Jensen, A. C. Try
FULL PAPER
168.4 ppm. C23H26N2O4 (394.46): calcd. C 70.03, H 6.64, N 7.10;
found C 69.92, H 6.70, N 7.10.
(Ϯ)-17 (250 mg, 11%) as a white solid; m.p. 132–134 °C. 1H NMR
(400 MHz, CDCl3, 25 °C): δ = 1.41 (t, J = 7.1 Hz, 6 H, 2ϫ CH3),
3.73 (s, 6 H, 2ϫ OCH3), 4.35–4.44 (m, 8 H, 4ϫ CH2), 4.70 (d, J
= 17.6 Hz, 2 H, CH2), 6.63 (d, J = 3.0 Hz, 2 H, ArH), 7.27 (d, J
= 3.0 Hz, 2 H, ArH) ppm. 13C NMR (100 MHz, CDCl3, 25 °C):
δ = 14.3, 55.5, 57.8, 61.1, 67.6, 115.5, 115.6, 127.2, 130.8, 155.4,
165.8 ppm. C23H26N2O6 (426.46): calcd. C 64.78, H 6.15, N 6.57;
found C 64.65, H 6.29, N 6.88.
Diethyl 6H,12H-5,11-Methanodibenzo[b,f][1,5]diazocine-1,7-dicarb-
oxylate (13): With ethyl 3-aminobenzoate (2.0 g, 12.1 mmol), para-
formaldehyde (582 mg, 19.38 mmol) and trifluoroacetic acid
(75 mL). The crude material was purified by recrystallisation from
hexane to afford (Ϯ)-13 (760 mg, 34%) as a white solid; m.p. 168–
170 °C. 1H NMR (400 MHz, CDCl3, 25 °C): δ = 1.36 (t, J =
7.1 Hz, 6 H, 2ϫ CH3), 4.25–4.34 (m, 6 H, 3ϫ CH2), 4.67 (d, J =
18.0 Hz, 2 H, CH2), 4.97 (d, J = 18.0 Hz, 2 H, CH2), 7.22 (app. t,
J = 8.0 Hz, 2 H, ArH), 7.37 (d, J = 8.0 Hz, 2 H, ArH), 7.69 (d, J
= 8.0 Hz, 2 H, ArH) ppm. 13C NMR (100 MHz, CDCl3, 25 °C): δ
= 14.3, 59.1, 60.8, 65.2, 126.9, 127.0, 128.6, 129.7, 130.2, 148.8,
166.5 ppm. C21H22N2O4 (366.41): calcd. C 68.84, H 6.05, N 7.65;
found C 69.11, H 6.06, N 7.78.
Type I, III and IV Dihexyl Ester Compounds
Dihexyl 4,10-Dimethyl-6H,12H-5,11-methanodibenzo[b,f][1,5]diazo-
cine-1,7-dicarboxylate (18): With hexyl 3-amino-4-methylbenzoate
(444 mg, 1.89 mmol), paraformaldehyde (91 mg, 3.03 mmol) and
trifluoroacetic acid (10 mL). The crude material was chromato-
graphed (silica gel; hexane/dichloromethane, 1:1) to afford (Ϯ)-18
1
(326 mg, 68%) as a pale yellow oil. H NMR (400 MHz, CDCl3,
25 °C): δ = 0.89 (t, J = 6.7 Hz, 6 H, 2ϫ CH3), 1.30–1.38 (m, 8 H,
4ϫ CH2), 1.39–1.46 (m, 4 H, 2ϫ CH2), 1.71 (quin, J = 6.8 Hz, 4
H, 2ϫ CH2), 2.49 (s, 6 H, 2ϫ CH3), 4.16–4.27 (m, 4 H, 2ϫ CH2),
4.30 (s, 2 H, CH2), 4.53 (d, J = 18.3 Hz, 2 H, CH2), 4.83 (d, J =
18.3 Hz, 2 H, CH2), 7.12 (d, J = 8.0 Hz, 2 H, ArH), 7.65 (d, J =
8.0 Hz, 2 H, ArH) ppm. 13C NMR (100 MHz, CDCl3, 25 °C): δ =
14.03, 18.01, 22.57, 25.83, 28.72, 31.49, 55.23, 64.84, 65.69, 126.04,
126.61, 128.75, 130.84, 138.78, 147.15, 166.83 ppm. C31H42N2O4
(506.68): calcd. C 73.49, H 8.36, N 5.53; found C 73.40, H 8.25, N
5.46.
Type III Compounds
Diethyl 4,10-Dimethyl-6H,12H-5,11-methanodibenzo[b,f][1,5]diazo-
cine-3,9-dicarboxylate (14): With ethyl 3-amino-2-methylbenzoate
(1.65 g, 9.21 mmol), paraformaldehyde (442 mg, 14.73 mmol) and
trifluoroacetic acid (30 mL). The crude material was chromato-
graphed (silica gel; dichloromethane) to afford (Ϯ)-14 (907 mg,
50%) as a white solid; m.p. 122–124 °C. 1H NMR (400 MHz,
CDCl3, 25 °C): δ = 1.37 (t, J = 7.1 Hz, 6 H, 2ϫ CH3), 2.63 (s, 6
H, 2ϫ CH3), 3.96 (d, J = 16.8 Hz, 2 H, CH2), 4.30–4.36 (m, 6 H,
3ϫ CH2), 4.61 (d, J = 16.8 Hz, 2 H, CH2), 6.80 (d, J = 8.0 Hz, 2
H, ArH), 7.49 (d, J = 8.0 Hz, 2 H, ArH) ppm. 13C NMR
(100 MHz, CDCl3, 25 °C): δ = 14.3, 14.5, 55.5, 60.8, 67.4, 124.0,
125.4, 130.2, 131.9, 134.8, 146.6, 167.9 ppm. C23H26N2O4 (394.46):
calcd. C 70.03, H 6.64, N 7.10; found C 70.22, H 6.70, N 7.24.
Dihexyl 4,10-Dimethoxy-6H,12H-5,11-methanodibenzo[b,f][1,5]di-
azocine-1,7-dicarboxylate (19): With hexyl 3-amino-4-methoxyben-
zoate (395 mg, 1.57 mmol), paraformaldehyde (76 mg, 2.51 mmol)
and trifluoroacetic acid (10 mL). The crude material was chromato-
graphed (silica; ethyl acetate/dichloromethane, 1:9) to afford (Ϯ)-
19 (174 mg, 41%) as a white solid; m.p. 143–144 °C. 1H NMR
(400 MHz, CDCl3, 25 °C): δ = 0.90 (t, J = 7.1 Hz, 6 H, 2ϫ CH3),
1.30–1.35 (m, 8 H, 4ϫ CH2), 1.38–1.46 (m, 4 H, 2ϫ CH2), 1.72
(quin, J = 6.8 Hz, 4 H, 2ϫ CH2), 3.98 (s, 6 H, 2ϫ OCH3), 4.15–
4.30 (m, 4 H, 2ϫ CH2), 4.31 (s, 2 H, CH2), 4.75 (d, J = 18.6 Hz,
2 H, CH2), 4.81 (d, J = 18.6 Hz, 2 H, CH2), 6.77 (d, J = 8.7 Hz, 2
H, ArH), 7.79 (d, J = 8.7 Hz, 2 H, ArH) ppm. 13C NMR
(100 MHz, CDCl3, 25 °C): δ = 14.02, 22.54, 25.77, 28.70, 31.47,
54.60, 55.94, 64.74, 66.14, 107.97, 120.61, 128.34, 132.19, 136.34,
156.38, 166.55 ppm. C31H42N2O6 (538.68): calcd. C 69.12, H 7.86,
N 5.20; found C 69.18, H 7.82, N 5.29.
Diethyl 4,10-Dimethoxy-6H,12H-5,11-methanodibenzo[b,f][1,5]di-
azocine-3,9-dicarboxylate (15): With ethyl 3-amino-2-methoxyben-
zoate (638 mg, 3.23 mmol), paraformaldehyde (160 mg, 5.23 mmol)
and trifluoroacetic acid (30 mL). The crude material was chromato-
graphed (silica gel; ethyl acetate/dichloromethane, 1:4) to afford
(Ϯ)-15 (420 mg, 61%) as a white solid; m.p. 112–114 °C. 1H NMR
(400 MHz, CDCl3, 25 °C): δ = 1.37 (t, J = 7.1 Hz, 6 H, 2ϫ CH3),
4.02 (s, 6 H, 2ϫ OCH3), 4.29–4.41 (m, 8 H, 4ϫ CH2), 4.55 (d, J
= 17.5 Hz, 2 H, CH2), 6.69 (d, J = 8.0 Hz, 2 H, ArH), 7.40 (d, J
= 8.0 Hz, 2 H, ArH) ppm. 13C NMR (100 MHz, CDCl3, 25 °C):
δ = 14.2, 54.9, 60.9, 61.2, 67.6, 122.1, 123.7, 125.7, 134.2, 153.8,
166.1 ppm. C23H26N2O6 (426.46): calcd. C 64.78, H 6.15, N 6.57;
found C 64.92, H 6.13, N 6.65.
Dihexyl 2,8-Dimethyl-6H,12H-5,11-methanodibenzo[b,f][1,5]diazo-
cine-1,7-dicarboxylate (20): With hexyl 5-amino-2-methylbenzoate
(443 mg, 1.89 mmol), paraformaldehyde (91 mg, 3.04 mmol) and
trifluoroacetic acid (15 mL). The crude material was chromato-
graphed (silica; ethyl acetate/dichloromethane, 1:20 then 1:10) to
afford (Ϯ)-20 (68 mg, 14%) as a pale yellow oil. 1H NMR
(400 MHz, CDCl3, 25 °C): δ = 0.90 (t, J = 6.7 Hz, 6 H, 2ϫ CH3),
1.30–1.43 (m, 12 H, 6ϫ CH2), 1.71 (quin, J = 6.8 Hz, 4 H, 2ϫ
CH2), 2.24 (s, 6 H, 2ϫ CH3), 4.12 (d, J = 17.0 Hz, 2 H, CH2),
4.24–4.32 (m, 6 H, 3ϫ CH2), 4.69 (d, J = 17.0 Hz, 2 H, CH2), 7.01
(d, J = 8.3 Hz, 2 H, ArH), 7.06 (d, J = 8.3 Hz, 2 H, ArH) ppm.
13C NMR (100 MHz, CDCl3, 25 °C): δ = 14.07, 19.64, 22.58, 25.78,
28.61, 31.45, 57.45, 65.33, 65.94, 125.43, 126.70, 129.77, 131.58,
131.67, 145.85, 168.72 ppm. C31H42N2O4 (506.68): calcd. C 73.49,
H 8.36, N 5.53; found C 73.52, H 8.26, N 5.93.
Type IV Compounds
Diethyl 2,8-Dimethyl-6H,12H-5,11-methanodibenzo[b,f][1,5]diazo-
cine-4,10-dicarboxylate (16): With ethyl 2-amino-5-methylbenzoate
(4.40 g, 24.55 mmol), paraformaldehyde (1.18 g, 39.28 mmol) and
trifluoroacetic acid (70 mL). The crude material was chromato-
graphed (silica gel; dichloromethane) to afford (Ϯ)-16 (824 mg,
17%) as a white solid; m.p. 188–190 °C. 1H NMR (400 MHz,
CDCl3, 25 °C): δ = 1.39 (t, J = 7.1 Hz, 6 H, 2ϫ CH3), 2.33 (s, 6
H, 2ϫ CH3), 4.28–4.39 (m, 8 H, 4ϫ CH2), 4.74 (d, J = 17.5 Hz, 2
H, CH2), 6.81 (d, J = 1.5 Hz, 2 H, ArH), 7.45 (d, J = 1.5 Hz, 2 H,
ArH) ppm. 13C NMR (100 MHz, CDCl3, 25 °C): δ = 14.3, 20.6,
57.6, 60.9, 67.3, 125.8, 129.4, 130.3, 131.6, 132.3, 133.2, 166.2 ppm.
C23H26N2O4 (394.46): calcd. C 70.0, H 6.64, N 7.10; found C 70.21,
H 6.84, N 7.18.
Dihexyl 6H,12H-5,11-Methanodibenzo[b,f][1,5]diazocine (21) and
1,9-Bis(hexoxycarbonyl)-6H,12H-5,11-methanodibenzo[b,f][1,5]di-
azocine-1,7-dicarboxylate (26): With hexyl 3-aminobenzoate
(444 mg, 2.0 mmol), paraformaldehyde (96 mg, 3.2 mmol) and tri-
fluoroacetic acid. The crude material was chromatographed (silica
gel; dichloromethane/ethyl acetate, 9:1) to afford to afford an mix-
Diethyl 2,8-Dimethoxy-6H,12H-5,11-methanodibenzo[b,f][1,5]diazo-
cine-4,10-dicarboxylate (17): With ethyl 2-amino-5-methoxybenzo-
ate (2.00 g, 10.25 mmol), paraformaldehyde (492 mg, 16.40 mmol)
and trifluoroacetic acid (55 mL). The crude material was chromato-
graphed (silica gel; ethyl acetate/dichloromethane, 1:1) to afford
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Eur. J. Org. Chem. 2010, 4662–4670