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DOI: 10.1055/s-2003-36796
Novel Microwave-assisted [3+3] Cyclocondensations with 1-Cyanomethylene Tetrahydroisoquinoline
Publikationsverlauf
Publikationsdatum:
22. Januar 2003 (online)
Abstract
α,β-Unsaturated aldehydes and ketones react with 1-cyanomethylene-6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline in microwave-enhanced reactions affording regioselectively 6,7-dihydro-4H-benzo[a]quinolizines and 6,7-dihydro-2H-benzo[a]quinolizines, respectively.
Key words
β-enaminonitriles - [3+3] cyclisations - Michael additions - microwave heating - benzo[a]quinolizines
- 1
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References
Experimental procedure: 2.4 mmol (520 mg) of 1 was mixed with 3.2 mmol of the carbonyl compound, and the reaction mixture was irradiated in an open vessel for 4 minutes in a Synthewave S402 (Prolabo) monomode, focused MW (2,45 GHz) reactor with continuous rotation. During the irradiation, the temperature of the reaction mixture (measured by infrared thermometry) raised linearly and reached its maximum between 140-170 °C depending on the enone after ca. 180 seconds. The oily mixture was then cooled and the product was either crystallised from an appropriate solvent (EtOH) or purified by flash chromatography. Yield: 72-85%.
10All isolated compounds were fully
characterised by 1H and 13C
NMR analysis. Representative data are given as follows: 4b: 1H NMR δ = 7.88
(s, 1 H, H-11), 7.37 (d, 1 H, J = 1.8
Hz, 4-furanyl), 6.64 (s, 1 H, H-8), 6.32 (dd, 1 H, 4-furanyl), 6.30 (d,
1 H, 4-furanyl), 6.28 (d, 1 H, H-2), 5.28 (dd, 1 H, H-3), 5.20 (d,
1 H, H-4), 3.94 (s, 3 H, 9-MeO), 3.90 (s, 3 H, 10-MeO), 3.41 (m,
1 H, H-6), 3.40 (m, 1 H, H-6), 2.89 (dd, 1 H, H-7), 2.74 (dt, 1
H, H-7); 13C NMR δ = 153.7
(4-furanyl), 150.6 (C-9), 150.2 (C-11b), 147.3 (C-10), 142.6 (4-furanyl), 129.5
(C-7a), 125.5 (C-2), 123.6 (1-CN), 121.0 (C-11a), 111.0 (C-11),
110.5 (4-furanyl), 110.1 (C-3), 110.0 (C-8), 108.5 (4-furanyl),
74.9 (C-1), 57.6 (C-4), 56.2 (9-MeO), 56.0 (10-MeO), 48.0 (C-6),
29.4 (C-7). 3 (R4 = 2-furanyl, R1,
R2, R3 = H): 1H
NMR δ = 7.87 (s, 1 H, H-11),
7.39 (d, 1 H, J = 2.0
Hz, 2-furanyl), 6.65 (s, 1 H, H-8), 6.34 (dd, 1 H, 2-furanyl), 6.18
(d, 1 H, 2-furanyl), 6.09 (d, 1 H, H-4), 4.87 (dd, 1 H, H-3), 4.53
(d, 1 H, H-2), 3.93 (s, 3 H, 9-MeO), 3.90 (s, 3 H, 10-MeO), 3.52
(m, 1 H, H-6), 3.42 (m, 1 H, H-6), 2.90 (m, 1 H, H-7), 2.76 (m,
1 H, H-7); 13C NMR δ = 157.6 (2-furanyl),
150.5 (C-9), 147.4 (C-10), 146.3 (C-11b), 142.1 (2-furanyl), 130.7
(C-4), 130.0 (C-7a), 123.3 (1-CN), 120.1 (C-11a), 111.3 (C-11),
110.3 (C-8), 110.4 (2-furanyl), 105.5 (2-furanyl), 100.4 (C-3),
73.6 (C-1), 56.3 (9-MeO), 56.0 (10-MeO), 48.8 (C-6), 36.2 (C-2),
29.4 (C-7). 5a: 1H
NMR δ = 8.11 (d, 2 H, H-2′′),
8.09 (d, 1 H, J = 8.4
Hz, H-4), 7.82 (d, 1 H, J = 8.4
Hz, H-5), 7.51 (t, 1 H, H-4′′), 7.50 (t, 2 H,
H-3′′), 7.22 (s, 1 H, H-5′), 7.02 (s,
1 H, H-2′), 6.68 (dd, 1 H, J = 11.0;
17.4 Hz, CH=), 5.64 (d, 1 H, J = 17.4 Hz,
CH
2=), 5.20 (d, 1
H, J = 11.0
Hz, CH
2=), 4.00 (s,
3 H, 4′-MeO), 3.95 (s, 3 H, 3′-MeO); 13C
NMR δ = 161.9 (C-2), 159.6 (C-6), 150.4
(C-4′), 148.8 (C-3′), 141.7 (C-4), 137.6 (C-1′′),
134.3 (CH=), 130.8 (C-3′′),
130.1 (C-6′), 129.3 (C-1′), 129.2 (C-4′′),
127.7 (C-2′′), 118.0 (C-5), 117.6 (3-CN), 114.7
(CH2=), 112.9 (C-2′),
108.8 (C-5′), 108.3 (C-3), 56.3 (3′-MeO), 56.2 (4′-MeO). 6 E: 1H
NMR δ = 7.94 (s, 1 H, H-8),
7.43 (d, 2 H, Ph), 7.31 (t, 2 H, Ph), 7.20 (t, 1 H, Ph), 6.86 (d,
1 H, H-3′), 6.81 (d, 1 H, H-2′), 6.70 (s, 1 H,
H-5), 5.41 (s, 1 H, H-2), 3.98 (s, 3 H, 7-MeO), 3.93 (s, 3 H, 6-MeO),
3.41 (t, 2 H, H-3), 2.83 (dd, 2 H, H-4); 13C
NMR δ = 151.6 (C-1), 151.0 (C-6), 147.4
(C-7), 137.7 (Ph), 131.2 (C-4a), 128.6 (Ph), 127.0 (C-3′),
126.9 (Ph), 126.0 (Ph), 122.0 (1′-CN), 120.5 (C-8a), 120.3
(C-2′), 111.9 (C-8), 110.6 (C-5), 76.9 (C-1′),
56.3
(7-MeO), 56.0 (6-MeO), 39.6 (C-3), 29.9 (C-4). 6 Z: 1H NMR δ = 7.30
(d, 2 H, Ph), 7.27 (t, 2 H, Ph), 7.18 (s, 1 H, H-8), 7.13 (t, 1
H, Ph), 7.11 (d, 1 H, H-2′), 6.78 (s, 1 H, H-5), 6.61 (d,
1 H, H-3′), 5.80 (s, 1 H, H-2), 3.96 (s, 3 H, 7-MeO), 3.83
(s, 3 H, 6-MeO), 3.40 (t, 2 H, H-3), 2.83 (dd, 2 H, H-4); 13C
NMR δ = 151.6 (C-1), 151.0 (C-6),
147.2 (C-7), 138.1 (Ph), 131.8 (C-4a), 128.6 (Ph), 123.4 (C-2′),
126.2 (Ph), 125.3 (Ph), 122.0 (1′-CN), 120.6 (C-8a), 123.7
(C-3′), 113.2 (C-8), 110.8 (C-5), 77.2 (C-1′),
56.3 (7-MeO), 56.0 (6-MeO), 39.6 (C-3), 30.1 (C-4).