Heck Reaction of Protected Hydroxychromones
655
nitrogen or argon. When the starting material disappeared the
reaction was worked up as given for Conditions A.
Further details of coupling reactions are shown in Table 1.
(C-7), 176.9 (C-4). Anal. Calc. for C24H18O3: C 81.34, H 5.12.
Found: C 81.27, H 5.07%.
Ethyl (E)-3-[7-(Methoxymethoxy)-4-oxo-4H-1-benzopyran-
6-yl]acrylate (18c)
(E)-7-Hydroxy-6-styrylchromone (12)
Yield: 9.2% (Conditions B, reaction period: 36.5 h, conversion:
93%, elution: chloroform/acetone, 8/1), 6.8% (Conditions C,
reaction period: 5 h, conversion: 48%, elution: chloroform/
acetone, 8/1). mp 262–2648C. nmax (KBr)/cmꢀ1 2610 (OH),
1628 (C¼O), 1614 (C¼C), 1556, 1478, 1400, 1310, 1304, 1260,
848, 820. dH ((D6)DMSO) 6.24 (d, J 5.5, 1H, 3-H), 6.95 (s, 1H,
8-H), 7.37–7.41 (m, 5H, a-H, b-H, Ph), 7.62 (d, J 7.0, 2H,
20,60-H), 8.16 (d, J 5.5, 1H, 2-H), 8.21 (s, 1H, 5-H), 11.25 (s, 1H,
7-OH). dC ((D6)DMSO) 103.5 (C-8), 112.8 (C-3), 118.2 (C-6),
123.0, 123.8 (C-a, C-b), 124.9 (C-4a), 127.5 (C-20,60), 128.7
(C-40), 129.7 (C-30,50), 130.9 (C-5), 138.2 (C-10), 157.0 (C-2),
157.6 (C-8a), 161.0 (C-7), 176.6 (C-4). Anal. Calc. for
C17H12O3: C 77.26, H 4.58. Found: C 77.20, H 4.31%.
Yield: 22% (Conditions A, reaction period: 4 h, conversion:
76%, elution: toluene/ethyl acetate, 6/1, v/v), 8.1% (Conditions
C, reaction period: 4 h, conversion: 76%, elution: toluene/acetic
acid, 18/1, v/v). mp 113–1148C. nmax (KBr)/cmꢀ1 2969, 1716
(C¼O, ester), 1659 (C¼O), 1620 (C¼C), 1598, 1448, 1300,
1288, 1261 (C–O–C), 1240, 1210, 1169, 1053 (C–O–C), 923,
832. dH (CDCl3) 1.35 (t, J 7.0, 3H, CH2CH3), 3.53 (s, 3H,
OCH3), 4.28 (q, J 7.0, 2H, CH2CH3), 5.35 (s, 2H, OCH2O), 6.30
(d, J 5.8, 1H, 30-H), 6.63 (d, J 16.1, 1H, 2-H), 7.18 (s, 1H, 80-H),
7.79 (d, J 5.8, 1H, 20-H), 8.00 (d, J 16.1, 1H, 3-H), 8.39
(s, 1H, 50-H). dC (CDCl3) 14.3 (CH2CH3), 56.6 (OCH3), 60.5
(CH2CH3), 94.7 (OCH2O), 102.6 (C-80), 113.0 (C-30), 119.2
(C-60), 120.6 (C-3), 123.1 (C-4a0), 125.9 (C-50), 137.8 (C-2),
155.0 (C-20), 158.4, 159.6 (C-70, C-8a0), 166.9 (C-1), 176.6
(C-40). Anal. Calc. for C16H16O6: C 63.15, H 5.30. Found:
C 62.97, H 5.17%.
2-Phenyl-5H-furo[3,2-g]chromen-5-one (13)
Yield: 5% (from chromone 6, using Conditions C, reaction
period: 5 h, isolated as a by-product in addition to cross-coupled
product 12), 7% (from chromone 14a, using Conditions C,
reaction period: 30 min, isolated as a by-product in addition to
the free phenolic product 6). Yellow crystals, mp 269–2728C.
Ethyl (E)-3-(7-Hydroxy-4-oxo-4H-1-benzopyran-6-yl)
acrylate (21)
Yield: 15% (Conditions C, reaction period: 4 h, conversion:
76%, elution: toluene/acetic acid, 18/1, v/v). Isolated as a by-
product in addition to the protected product 18c. mp 239–2418C
(dec.). nmax (KBr)/cmꢀ1 3075 (OH), 1711 (C¼O, ester), 1617
(C¼O, chromone þ C¼C), 1583, 1465, 1400, 1368, 1350, 1305,
1262 (C–O–C), 1179, 1048 (C–O–C), 870. dH ((D6)DMSO)
1.26 (t, J 7.0, 3H, CH2CH3), 4.19 (q, J 7.0, 2H, CH2CH3), 6.24
(d, J 6.3, 1H, 30-H), 6.72 (d, J 16.2, 1H, 2-H), 6.97 (s, 1H, 80-H),
7.84 (d, J 16.2, 1H, 3-H), 8.15 (d, J 6.3, 1H, 20-H), 8.19 (s, 1H,
50-H), 11.60 (vbr s, 1H, OH). dC ((D6)DMSO) 15.1 (CH2CH3),
61.0 (CH2CH3), 104.0 (C-80), 113.0 (C-30), 118.1 (C-60), 120.3
(C-3), 121.7 (C-4a0), 127.4 (C-50), 139.6 (C-2), 158.0 (C-20),
159.0 (C-8a0), 162.5 (C-70), 167.3 (C-1), 176.4 (C-40). Anal.
Calc. for C14H12O5: C 64.61, H 4.65. Found: C 64.37, H 4.92%.
n
max (KBr)/cmꢀ1 1644 (C¼O), 1622 (C¼C), 1472, 1300, 868,
828, 764. dH (CDCl3) 6.35 (d, J 6.3, 1H, 3-H), 7.13 (s, 1H, 9-H),
7.39–7.51 (m, 3H, 30,50,40-H), 7.58 (s, 1H, 3-H), 7.89 (over-
lapping s and d, 3H, 7-H and 20,60-H), 8.43 (s, 1H, 4-H). dC
(CDCl3) 99.8, 101.1 (C-3, C-9), 111.9 (C-6), 117.7 (C-4), 121.6
(C-3a), 125.2 (C-20,60), 128.0 (C-4a), 128.9 (C-30,50), 129.4 (C-
40), 129.5 (C-10), 154.5 (C-8a), 155.3 (C-7), 157.4, 158.8 (C-2,
C-9a), 177.9 (C-5). Anal. Calc. for C17H10O3: C 77.85, H 3.84.
Found: C 77.56, H 3.99%.
(E)-7-Methoxymethoxy-6-styrylchromone (17c)
Yield: 70% (Conditions C, reaction period: 1 h), mp 129–1318C.
n
max (KBr)/cmꢀ1 3050 (sp2 CH) 2943, 2900, 1640 (C¼O), 1618
(C¼C), 1594, 1474, 1457, 1300, 1278, 1244 (C–O–C), 1227 (C–
O–C), 1203, 1146, 1090 (C–O–C), 1039, 974, 918, 831. dH
(CDCl3) 3.52 (s, 3H, CH3), 5.33 (s, 2H, CH2), 6.27 (d, J 5.8, 1H,
3-H), 7.13 (s, 1H, 8-H), 7.22–7.44 (m, a-H, b-H, 30,50,40-H) 7.54
(d, J 7.4, 2H, 20,60-H), 7.75 (d, J 5.8, 1H, 2-H), 8.40 (s, 1H, 5-H).
dC (CDCl3) 56.5 (CH3), 94.6 (CH2), 102.2 (C-8), 112.7 (C-3),
119.2 (C-6), 121.1, 122.7 (C-a, C-b), 126.1 (C-4a), 126.6
(C-20,60), 127.8 (C-40), 128.6 (C-30,50), 131.0 (C-5), 137.2
(C-10), 154.9 (C-2), 157.0, 158.6 (C-7, C-8a), 176.9 (C-4).
Anal. Calc. for C19H16O4: C 74.01, H 5.23. Found: C 74.19, H
5.99%.
Ethyl (E)-3-(7-Benzyloxy-4-oxo-4H-1-benzopyran-6-yl)
acrylate (18d)
Yield: 54% (Conditions C, reaction period: 90 min at 1008C, and
then 2.5 h at 1358C), mp 183.5–185.58C. nmax (KBr)/cmꢀ1 2979,
1710 (C¼O, ester), 1655 (C¼O, chromone), 1620 (C¼C), 1601,
1455, 1294, 1248 (C–O–C), 1175, 1057 (C–O–C), 833. dH
(CDCl3) 1.33 (t, J 6.9, 3H, CH2CH3), 4.26 (q, J 6.9, 2H,
CH2CH3), 5.25 (s, 2H, CH2), 6.29 (d, J 5.5, 1H, 30-H), 6.65 (d, J
16.6, 1H, 2-H), 6.90 (s, 1H, 80-H), 7.37–7.48 (m, 5H, Ph), 7.76
(d, J 5.5, 1H, 20-H), 8.05 (d, J 16.6, 1H, 3-H), 8.38 (s, 1H, 50-H).
dC (CDCl3) 14.2 (CH3), 60.5 (CH2CH3), 71.0 (PhCH2), 100.6
(C-80), 113.1 (C-30), 118.6 (C-60), 120.7 (C-2), 123.0 (C-4a0),
126.1, 128.4 (C-50, C-40), 127.2 (C-20,60), 128.8 (C-30,50), 135.1
(C-10), 137.8 (C-3), 154.8 (C-20), 158.6 (C-8a0), 161.0 (C-70),
166.9 (C-1), 176.5 (C-40). Anal. Calc. for C21H18O5: C 71.99,
H 5.18. Found: C 72.20, H 4.93%.
(E)-7-Benzyloxy-6-styrylchromone (17d)
Yield: 82% (Conditions C, reaction period: 30 min, elution:
ethyl acetate), mp 142–1448C. nmax (KBr)/cmꢀ1 3058, 1648
(C¼O), 1618 (C¼C), 1595, 1457, 1297, 1260, 1241 (C–O–C),
1057 (C–O–C), 830. dH (CDCl3) 5.18 (s, 2H, CH2), 6.25 (d, J
6.3, 1H, 3-H), 6.84 (s, 1H, 8-H), 7.23–7.49 (m, 12H, 2 ꢂ Ph, a-
H, b-H), 7.71 (d, J 6.3, 1H, 2-H), 8.38 (s, 1H, 5-H). dC (CDCl3)
70.7 (CH2), 100.0 (C-8), 112.8 (C-3), 118.6 (C-6), 121.3 (C-b),
122.9 (C-a), 125.9 (C-4a), 126.6, 127.2 (C-20,60, C-20,60), 127.7,
128.3 (C-40, C-40), 128.6, 128.7 (C-30,50, C-30,50), 131.1 (C-5),
135.5 (C-10), 137.2 (C-10), 154.6 (C-2), 157.1 (C-8a), 160.2
(E)-3-[7-(Methoxymethoxy)-4-oxo-4H-1-benzopyran-6-yl]-
2-propenal (19c)
Yield: 18% (Conditions C, reaction period: 35 min, conversion:
93%, elution: toluene/ethyl acetate, 12/1, v/v). mp 160–1628C.
nmax (KBr)/cmꢀ1 2907, 2828, 1728 (C¼O, aldehyde), 1676