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Chromene 3 f
General procedure for the NHC-catalyzed hydroacylation
reaction of allenals 5: Preparation of chromones 8
Obtained from allenal 1 f (170 mg, 0.89 mmol). After chromatogra-
phy of the residue using hexanes/ethyl acetate (12:1) as eluent,
compound 3 f (75 mg, 44%) was obtained as a yellow oil. H NMR
DBU (15 mg, 0.10 mmol, 15 mL) was added at room temperature to
a stirred solution of imidazolium chloride 6 (0.05 mmol) in 1,4-diox-
ane (2 mL). After 10 min, the appropriate 2-(propa-1,2-dienyloxy)-
benzaldehyde 5 (1.0 mmol) in 1,4-dioxane (1 mL) was added. The
reaction mixture was stirred until complete disappearance (by TLC)
of the starting material and filtered through a pack of Celite. The
filtrate was extracted with ethyl acetate (3ꢅ5 mL), and the com-
bined extracts were washed twice with brine and dried (MgSO4).
The solvent was removed under reduced pressure, and analytically
pure adducts 8 were obtained after purification by flash chroma-
tography on silica gel using hexanes/ethyl acetate mixtures.
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(300 MHz, [D6]acetone, 258C): d=8.04 (dd, J=8.8, 2.6 Hz, 1H), 7.97
(d, J=2.8 Hz, 1H), 6.89 (d, J=8.8 Hz, 1H) 5.83 (m, 1H), 4.96 (m,
2H), 2.08 ppm (q, J=1.9 Hz, 3H); 13C NMR (75 MHz, [D6]acetone,
258C): d=160.7, 128.9, 126.5, 125.9, 124.7, 121.7, 119.8, 116.8,
116.0, 67.4, 17.8 ppm; IR (CHCl3): n˜ =2936, 1490, 1220, 750 cmꢀ1
;
HRMS (ES): m/z calcd for C10H9NO3 [M]+: 191.0582; found:
191.0590.
Chromene 3g
Obtained from allenal 1g (200 mg, 1.37 mmol). After chromatogra-
phy of the residue using hexanes/ethyl acetate (3:1) as eluent,
compound 3g (80 mg, 40%) was obtained as a colorless oil.
1H NMR (300 MHz, CDCl3, 258C): d=7.14 (m, 2H), 6.92 (m, 2H), 6.81
(m, 1H), 5.59 (m, 1H), 4.76 (m, 2H), 2.29 (s, 3H), 2.04 ppm (m, 3H);
13C NMR (75 MHz, CDCl3, 258C): d=154.1, 130.2, 128.9, 124.3, 123.5,
121.1, 118.3, 115.7, 65.4, 17.9 ppm; IR (CHCl3): n˜ =3038, 1485, 1450,
1220, 750 cmꢀ1; HRMS (ES): m/z calcd for C10H10O [M]+: 146.0732;
found: 146.0729.
Chromone 8a
Obtained from allenal 5a (100 mg, 0.62 mmol). After chromatogra-
phy of the residue using hexanes/ethyl acetate (7:1) as eluent,
compound 8a (85 mg, 85%) was obtained as a pale brown solid.
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M.p. 70–718C; H NMR (300 MHz, CDCl3, 258C): d=8.22 (dd, J=1.7,
7.9 Hz, 1H), 7.78 (d, J=1.0 Hz, 1H), 7.62 (ddd, J=1.6, 7.0, 8.5 Hz,
1H), 7.37 (m, 2H), 2.02 ppm (d, J=1.0 Hz, 3H); 13C NMR (75 MHz,
CDCl3, 258C): d=178.2, 156.6, 151.7, 133.2, 125.7, 124.7, 123.5,
120.6, 117.9, 11.1 ppm; IR (CHCl3): n˜ =2924, 1641, 1467 cmꢀ1; HRMS
(ES): m/z calcd for C10H8O2 [M]+: 160.0524; found: 160.0524.
Chromene 3h
Chromone 8b
Obtained from allenal 1h (180 mg, 0.95 mmol). After chromatogra-
phy of the residue using hexanes/ethyl acetate (15:1) as eluent,
compound 3h (79 mg, 44%) was obtained as a yellow oil. H NMR
Obtained from allenal 5b (31 mg, 0.17 mmol). After chromatogra-
phy of the residue using hexanes/ethyl acetate (1:1) as eluent,
compound 8b (25 mg, 81%) was obtained as a pale brown solid.
M.p. 98–1008C; 1H NMR (300 MHz, CDCl3, 258C): d=8.12 (d, J=
8.9 Hz, 1H), 7.72 (d, J=1.2 Hz, 1H), 6.94 (dd, J=2.3, 8.9 Hz, 1H),
6.79 (d, J=2.3 Hz, 2H), 3.88 (s, 3H), 2.01 ppm (d, J=1.0 Hz, 3H);
13C NMR (75 MHz, CDCl3, 258C): d=177.7, 163.7, 158.8, 151.2, 127.1,
120.5, 117.6, 114.2, 99.9, 55.7, 11.1 ppm; IR (CHCl3): n˜ =2964, 1639,
1607 1440 cmꢀ1; HRMS (ES): m/z calcd for C11H10O3 [M]+: 190.0630;
found: 190.0623.
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(300 MHz, CDCl3, 258C): d=7.59 (dd, J=7.9, 1.7 Hz, 1H), 7.29 (dd,
J=7.6, 1.8 Hz, 1H), 6.94 (m, 1H), 5.66 (m, 1H), 4.84 (m, 2H), 2.61 (s,
3H), 2.04 ppm (q, J=1.6 Hz, 3H); 13C NMR (75 MHz, CDCl3, 258C):
d=199.5, 154.0, 130.0, 129.5, 127.5, 126.9, 125.1, 120.7, 118.5, 65.4,
31.8, 18.3 ppm; IR (CHCl3): n˜ =2926, 1672, 742 cmꢀ1; HRMS (ES):
m/z calcd for C12H12O2 [M]+: 188.0837; found: 188.0829.
Chromene 3i
Obtained from allenal 1i (150 mg, 0.73 mmol). After chromatogra-
phy of the residue using hexanes/ethyl acetate (15:1) as eluent,
compound 3i (78 mg, 52%) was obtained as a colorless oil.
1H NMR (300 MHz, [D6]acetone, 258C): d=10.22 (d, J=0.8 Hz, 1H),
7.64 (d, J=8.9 Hz, 1H), 6.76 (d, J=8.8 Hz, 1H), 5.69 (m, 1H), 4.64
(m, 2H), 3.93 (s, 3H), 2.16 ppm (q, J=1.6 Hz, 3H); 13C NMR
(75 MHz, [D6]acetone, 258C): d=187.9, 162.8, 160.2, 131.3, 129.0,
119.9, 119.5, 116.7, 106.3, 65.8, 56.3, 22.0 ppm; IR (CHCl3): n˜ =2927,
1656, 1459, 1322 cmꢀ1; HRMS (ES): m/z calcd for C12H12O3 [M]+:
204.0786; found: 204.0785.
Chromone 8c
Obtained from allenal 5c (42 mg, 0.22 mmol). After chromatogra-
phy of the residue using hexanes/ethyl acetate (4:1) as eluent,
compound 8c (26 mg, 62%) was obtained as a colorless solid. M.p.
96–988C; 1H NMR (300 MHz, CDCl3, 258C): d=8.18 (d, J=2.6 Hz,
1H), 7.80 (brs, 1H), 7.58 (dd, J=8.9, 2.6 Hz, 1H), 7.38 (d, J=8.9 Hz,
1H), 2.03 ppm (brs, 3H); 13C NMR (75 MHz, CDCl3, 258C): d=177.1,
154.9, 151.9, 133.5, 130.7, 125.1, 124.4, 120.9, 119.8, 11.1 ppm; IR
(CHCl3): n˜ =2925, 1639, 1611, 1486 cmꢀ1; HRMS (ES): m/z calcd for
C10H7ClO2 [M]+: 194.0135; found: 194.0128.
Chromene 3j
Chromone 8d
Obtained from allenal 1j (150 mg, 0.67 mmol). After chromatogra-
phy of the residue using hexanes/ethyl acetate (23:1) as eluent,
compound 3j (76 mg, 58%) was obtained as a colorless oil.
1H NMR (300 MHz, [D6]acetone, 258C): d=8.15 (d, J=8.6 Hz, 1H),
7.83 (m, 1H), 7.75 (m, 1H), 7.47 (ddd, J=8.5, 6.9, 1.5 Hz, 1H), 7.35
(ddd, J=8.1, 6.9, 1.2 Hz, 1H), 7.13 (d, J=8.9 Hz, 1H), 5.81 (m, 1H),
4.52 (m, 2H), 2.38 ppm (q, J=1.5 Hz, 3H); 13C NMR (75 MHz,
[D6]acetone, 258C): d=155.0, 133.0, 131.6, 131.3, 130.9, 129.7,
126.9, 124.1, 120.2, 119.3, 118.5, 64.9, 22.6 ppm; IR (CHCl3): n˜ =
2925, 1232, 750 cmꢀ1; HRMS (ES): m/z calcd for C14H12O [M]+:
196.0888; found: 196.0879.
Obtained from allenal 5d (76 mg, 0.35 mmol). After chromatogra-
phy of the residue using hexanes/ethyl acetate (5:1) as eluent,
compound 8d (42 mg, 55%) was obtained as a pale brown solid.
M.p. 145–1478C; 1H NMR (300 MHz, CDCl3, 258C): d=9.11 (d, J=
2.7 Hz, 1H), 8.48 (dd, J=2.8, 9.2 Hz, 1H), 7.86 (d, J=1.3 Hz, 1H),
7.59 (d, J=9.2 Hz, 1H), 2.08 ppm (d, J=1.2 Hz, 3H); 13C NMR
(75 MHz, CDCl3, 258C): d=176.8, 159.4, 151.9, 144.5, 127.6, 123.5,
122.7, 121.8, 119.8, 11.1 ppm; IR (CHCl3): n˜ =2973, 2926, 1639,
1600 cmꢀ1; HRMS (ES): m/z calcd for C10H7NO4 [M]+: 205.0375;
found: 205.0381.
Chem. Eur. J. 2014, 20, 1 – 10
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ꢂ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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