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9
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%.
10 All 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).