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General Procedure for the Synthesis of Chromones 2.
A solution of chromanone 1 (1 mmol) in diethoxymethyl acetate (1.0 g, 6 mmol) was heated at 140-150 °C for 15-20
min. After cooling, the resulting mixture was diluted with hexane (3 mL). The solid
product obtained on standing was collected by filtration, washed with hexane, and
dried. Spectral and analytical data for selected products follows.
3-(Difluoroacetyl)-4
H
-chromen-4-one(2a) and 3-(2,2-difluoro-1,1-dihydroxyethyl)-4
H
-chromen-4-one (
3a): IR (KBr): 3076, 1711, 1654, 1614, 1560 cm-1. 1H NMR (400 MHz, CDCl3/TMS): 2a (99%) δ = 6.97 (t, 1 H, CF2H, 2
J
H,F = 53.3 Hz), 7.54 (t, 1 H, H-6, o
J = 7.6 Hz), 7.57 (d, 1 H, H-8, o
J = 8.4 Hz), 7.79 (ddd, 1 H, H-7, o
J = 8.6, 7.2 Hz, m
J = 1.6 Hz), 8.30 (dd, 1 H, H-5, o
J = 8.0 Hz, m
J = 1.6 Hz), 8.68 (s, 1 H, H-2); 3a (1%) δ = 5.47 (s, 2 H, 2 OH), 5.78 (t, 1 H, CF2H, 2
J
H,F = 56.1 Hz), 8.35 (s, 1 H, H-2). 19F NMR (376 MHz, CDCl3/C6F6): 2a (98%) δ = 30.81 (d, HCF2, 2
J
F,H = 53.3 Hz); 3a (2%) δ = 28.72 (d, HCF2, 2
J
F,H = 56.1 Hz). 13C NMR (100 MHz, CDCl3): 2a δ = 109.03 (t, CF2, 1 J
C,F = 247.6 Hz), 118.45, 120.25, 124.74, 126.50, 126.97, 135.10, 155.84, 162.85, 174.42,
186.51 (t, COCF2, 2
J
C,F = 25.6 Hz). Anal. Calcd for C11H6F2O3: C, 58.94; H, 2.70. Found: C, 58.96; H, 2.67.
3-(Trifluoroacetyl)-4
H
-chromen-4-one(2c) and 3-(2,2,2-trifluoro-1,1-dihydroxyethyl)-4
H
-chromen-4-one (
3c): 1H NMR (400 MHz, CDCl3/TMS): 2c (50%) δ = 7.50-7.58 (m, 2 H, H-6, H-8), 7.79 (ddd, 1 H, H-7, o
J = 8.6, 7.0 Hz, m
J = 1.7 Hz), 8.30 (dd, 1 H, H-5, o
J = 8.0 Hz, m
J = 1.7 Hz), 8.62 (s, 1 H, H-2); 3c (50%) δ = 6.06 (s, 2 H, 2 OH), 7.50-7.58 (m, 2 H, H-6, H-8), 7.78 (ddd, 1 H, H-7,
o
J = 8.6, 7.0 Hz, m
J = 1.7 Hz), 8.26 (dd, 1 H, H-5, o
J = 8.0 Hz, m
J = 1.7 Hz), 8.40 (s, 1 H, H-2). 19F NMR (376 MHz, CDCl3/C6F6): 2c (50%) δ = 86.93 (s, CF3); 3c (50%) δ = 74.85 (s, CF3). Anal. Calcd for C11H5F3O3·0.25H2O: C, 53.56; H, 2.25. Found: C, 53.56; H, 2.29.
6-Methyl-3-(trifluoroacetyl)-4
H
-chromen-4-one(2d) and 3-(2,2,2-trifluoro-1,1-dihydroxyethyl)-4
H
-chromen-4-one (
3d): IR (KBr): 3309, 3059, 1718, 1664, 1635, 1601, 1558 cm-1. 1H NMR (400 MHz, CDCl3/TMS): 2d (70%) δ = 2.49 (s, 3 H, Me), 7.44 (d, 1 H, H-8, o
J = 8.6 Hz), 7.57 (ddq, 1 H, H-7, o
J = 8.6 Hz, m
J = 2.0 Hz, 4
J
H,CH3 = 0.6 Hz), 8.07 (dq, 1 H, H-5, m
J = 2.0 Hz, 4
J
H,CH3 = 0.6 Hz), 8.59 (s, 1 H, H-2); 3d (30%) δ = 2.49 (s, 3 H, Me), 6.16 (s, 2 H, 2 OH), 7.45 (d, 1 H, H-8, o
J = 8.6 Hz), 7.59 (ddq, 1 H, H-7, o
J = 8.6 Hz, m
J = 2.0 Hz, 4
J
H,CH3 = 0.6 Hz), 8.02 (dq, 1H, H-5, m
J = 2.0 Hz, 4
J
H,CH3 = 0.6 Hz), 8.37 (s, 1 H, H-2). Anal. Calcd for C12H7F3O3: C, 56.26; H, 2.75. Found: C, 55.98; H, 2.78.
3-(2,2,3,3-Tetrafluoropropanoyl)-4
H
-chromen-4-one(2g) and 3-(2,2,3,3-tetrafluoro-1,1-dihydroxypropyl)-4
H
-chromen-4-one (
3g): 1H NMR (400 MHz, CDCl3/TMS): 2g (94%) δ = 6.80 (tt, 1 H, CF2CF2H, 2
J
H,F = 53.3 Hz, 3
J
H,F = 5.8 Hz), 7.54 (ddd, 1 H, H-6, o
J = 8.0, 7.2 Hz, m
J = 1.0 Hz), 7.57 (ddd, 1 H, H-8, o
J = 8.5 Hz, m
J = 1.0 Hz, p
J = 0.4 Hz), 7.79 (ddd, 1 H, H-7, o
J = 8.6, 7.2 Hz, m
J = 1.7 Hz), 8.27 (ddd, 1 H, H-5, o
J = 8.0 Hz, m
J = 1.7 Hz, p
J = 0.4 Hz), 8.55 (s, 1 H, H-2); 3g (6%) δ = 6.28 (tt, 1 H, CF2CF2H, 2
J
H,F = 53.2 Hz, 3
J
H,F = 6.2 Hz), 6.31 (s, 2 H, 2 OH), 7.51 (ddd, 1 H, H-6, o
J = 8.0, 7.2 Hz, m
J = 1.0 Hz), 7.57 (dd, 1 H, H-8, o
J = 8.5 Hz, m
J = 1.0 Hz), 8.23 (dd, 1 H, H-5, o
J = 8.0 Hz, m
J = 1.7 Hz), 8.37 (s, 1 H, H-2). 19F NMR (376 MHz, CDCl3/C6F6): 2g (90%) δ = 24.06 (dt, HCF
2
CF2, 2
J
H,F = 53.3 Hz, 3
J
F,F = 7.3 Hz), 38.73 (td, HCF2
CF
2
, 3
J
F,F = 7.3 Hz, 3
J
F,H = 5.8 Hz); 3g (10%) δ = 25.39 (dt, HCF
2
CF2, 2
J
F,H = 53.1 Hz, 3
J
F,F = 7.7 Hz), 30.78 (q, HCF2
CF
2
, 3
J
F,F = 3
J
F,H = 7.0 Hz). 13C NMR (100 MHz, CDCl3): 2g δ = 109.07 (tt, CF2, 1
J
C,F = 252.0 Hz, 2
J
C,F = 30.5 Hz), 110.54 (tt, CF2, 1
J
C,F = 262.1 Hz, 2
J
C,F = 27.4 Hz), 118.40, 120.85, 124.61, 126.39, 127.03, 135.17, 155.69, 162.30 (t, C-2,
5
J
C,F = 2.2 Hz), 173.69, 185.58 (t, COCF2, 2
J
C,F = 29.3 Hz). Anal. Calcd for C12H6F4O3: C, 52.57; H, 2.21. Found: C, 52.46; H, 2.24.