Bruder et al.
JOCArticle
purification (lit.30 oil, bp not quoted): νmax (CHCl3)/cm-1 3073,
3009, 2961, 2933, 2859, 1473, 1428, 1112, 825, 615; δH (400
MHz; CDCl3) 7.71-7.69 (4 H, m), 7.47-7.38 (6 H, m),
5.32-5.30 (2 H, m), 4.32 (2 H, s), 4.04 (2 H, s), 1.08 (9 H, s);
δC (100 MHz; CDCl3) 144.4 (C), 135.5 (CH), 133.3 (C), 129.7
(CH), 127.7 (CH), 114.9 (CH2), 64.2 (CH2), 32.7 (CH2), 26.8
(Me), 19.3 (C); HRMS calcd for C20H2579BrOSi þ Naþ
411.0750, found MNaþ 411.0758.
115.8 (C), 108.7 (CH), 106.6 (C), 99.3 (CH), 71.0 (CH2), 65.7
(CH2), 21.1 (CH2), 20.5 (Me); HRMS calcd for C15H14O5 þ Naþ
297.0733, found MNaþ 297.0736.
7-Allyloxy-5-hydroxy-2-methyl-4H-chromen-4-one (17). To a
solution of noreugenin (11) (500 mg, 2.60 mmol) in DMF (26
mL) was added potassium carbonate (791 mg, 5.73 mmol),
followed by allyl bromide (0.5 mL, 5.73 mmol) at room tem-
perature under argon. After 3 h, the reaction mixture was
filtered and washed with a saturated aqueous ammonium
chloride solution (25 mL). The resulting mixture was extracted
into ethyl acetate (2 ꢀ 25 mL), and the combined organic
fractions were washed with brine (2 ꢀ 25 mL), dried over
magnesium sulfate, and evaporated in vacuo. The residue was
taken up in ethyl acetate (2 mL), and light petroleum was added
to precipitate the product. Filtration afforded the title com-
pound (243 mg, 40%) as a beige solid: mp 109-110 °C; νmax
(CHCl3)/cm-1 3009, 1664, 1626, 1591, 1505, 1417, 1388, 1342,
1267, 1166, 1114, 1078, 1028, 849; δH (400 MHz; CDCl3) 12.68
(1 H, s), 6.35 (1 H, d, J = 2.3), 6.33 (1 H, d, J = 2.3), 6.03 (1 H,
ddt, J = 17.3, 10.5, 5.3), 6.00 (1 H, s), 5.42 (1 H, ddt, J = 17.3,
1.5, 1.4), 5.32 (1 H, ddt, J = 10.5, 1.4, 1.3), 4.57 (2 H, dt, J = 5.3,
1.5), 2.33 (3 H, s); δC (100 MHz; CDCl3) 182.4 (C), 166.8 (C),
164.2 (C), 162.1 (C), 158.0 (C), 132.1 (CH), 118.4 (CH2), 108.7
(CH), 105.2 (C), 98.5 (C), 93.1 (CH), 69.1 (CH2), 20.5 (Me);
HRMS calcd for C13H12O4 þ Naþ 255.0628, found MNaþ
255.0622.
8-Allyl-7-[2-(tert-butyldiphenylsiloxy)methyl]allyloxy-5-hydro-
xy-2-methyl-4H-chromen-4-one (19). A solution of allyl ether 17
(166 mg, 0.72 mmol) in DMF (12 mL) was heated at 220 °C for
90 min in a microwave reactor (300 W). The solvent was
evaporated, and light petroleum/ethyl acetate (8:2) (50 mL)
was added to the resulting oil. After filtration through a short
pad of silica gel and evaporation of the filtrate, the resulting solid
was added to allylic bromide (583 mg, 1.50 mmol) and the
mixture was dissolved in DMF (2.3 mL). Potassium carbonate
(207 mg, 1.50 mmol) was added, and the mixture was stirred for
5 h at room temperature under argon. The reaction mixture was
filtered, diluted with ethyl acetate (3 mL), and washed with a
saturated aqueous ammonium chloride solution (3 mL) and
brine (5 mL). The organic fraction was dried over magnesium
sulfate and evaporatedin vacuo, and the resulting oil was purified
by chromatography (light petroleum/ethyl acetate, 9:1) to give
the title compound (171 mg, 45%) and the regioisomer 16 (45 mg,
18%) (data given previously) as colorless oils: νmax (CHCl3)/
cm-1 3691, 3009, 2932, 2859, 1660, 1620, 1592, 1427, 1387, 1327,
1269, 1192, 1113, 848; δH (400 MHz; CDCl3) 12.78 (1 H, s),
7.69-7.66 (4 H, m), 7.43-7.38 (6 H, m), 6.35 (1 H, s), 6.02 (1 H,
s), 5.77 (1 H, ddt, J = 17.0, 10.0, 6.2), 5.39 (1 H, s), 5.27 (1 H, s),
4.89 (1 H, dd, J = 17.0, 1.8), 4.85 (1 H, dd, J = 10.0, 1.8), 4.59 (2
H, s), 4.28 (2 H, s), 3.37 (2 H, d, J = 6.2), 2.35 (3 H, s), 1.08 (9 H,
s); δC (100 MHz; CDCl3) 182.9 (C), 166.7 (C), 161.6 (C), 160.7
(C), 154.9(C), 142.8 (C), 135.7 (CH), 135.5 (CH), 133.3(C), 129.7
(CH), 127.7 (CH), 114.6 (CH2), 112.8 (CH2), 108.3 (CH), 105.9
(C), 104.8 (C), 95.9 (CH), 69.2 (CH2), 64.5 (CH2), 26.8 (Me), 26.7
(CH2), 20.5 (Me), 19.3 (C); HRMS calcd for C33H36O5Si þ Hþ
541.2405, found MHþ 541.2384.
6-Allyl-7-[2-(tert-butyldiphenylsiloxy)methyl]allyloxy-5-hydro-
xy-2-methyl-4H-chromen-4-one 16. To a mixture of 14 (200 mg,
0.86 mmol) and the above bromide (894 mg, 1.72 mmol) in DMF
(2.9 mL) was added potassium carbonate (262 mg, 1.89 mmol) at
room temperature under argon. The reaction mixture was stirred
for 20 h, diluted with ether (20 mL), and washed with saturated
aqueous ammonium chloride (20 mL) and brine (2 ꢀ 20 mL).
After the organic layer was dried over magnesium sulfate and
reduced in vacuo, the resulting oil was purified by chromatogra-
phy (light petroleum/ethyl acetate/ether, 8:1:1) to give the title
compound (310 mg, 65%) as a colorless oil: νmax (CHCl3)/cm-1
3007, 2932, 2859, 1660, 1625, 1591, 1490, 1452, 1343, 1186, 1113,
910; δH (400 MHz; CDCl3) 12.83 (1 H, s), 7.70-7.67 (4 H, m),
7.44-7.36 (6 H, m), 6.38 (1 H, s), 6.04 (1 H, s), 5.85 (1 H, ddt, J =
17.1, 10.0, 6.2), 5.38 (1 H, s), 5.27(1 H, s), 4.93(1 H, ddt, J = 17.1,
1.9, 1.6), 4.86 (1 H, ddt, J = 10.0, 1.9, 1.4), 4.62 (2 H, s), 4.30 (2 H,
s), 3.35 (2 H, d, J = 6.2), 2.33 (3 H, s), 1.10 (9 H, s); δC (100 MHz;
CDCl3) 182.4 (C), 166.4 (C), 161.8 (C), 158.6 (C), 156.6 (C), 142.7
(C), 135.7 (CH), 135.5 (CH), 133.2 (C), 129.8 (CH), 127.7 (CH),
114.5 (CH2), 112.9 (CH2), 111.0 (C), 108.8 (CH), 105.1 (C), 90.4
(CH), 68.9 (CH2), 64.6 (CH2), 26.8 (Me), 26.4 (CH2), 20.4 (Me),
19.3 (C); HRMS calcd. for C33H36O5Si þ Naþ 563.2224, found
MNaþ 563.2207.
8-(tert-Butyldiphenylsiloxy)methyl-5-hydroxy-2-methyl-6,9-
dihydro-4H-oxepino[3,2-g]chromen-4-one. A mixture of diene
16 (60 mg, 0.11 mmol) and [1,3-bis-(2,4,6-trimethylphenyl)-
2-imidazolidinylidene](tricyclohexylphosphine)benzylideneru-
thenium(IV) dichloride (Grubbs’ II catalyst) (9.4 mg, 0.01
mmol) in dichloromethane (55 mL) was heated at 45 °C for
2 h under argon. The reaction mixture was evaporated in vacuo,
and the resulting oil was purified by chromatography (light
petroleum/ether, 75:25) to give the title compound (53 mg, 93%)
as a colorless oil: νmax (CHCl3)/cm-1 3690, 3012, 2933, 2860,
1654, 1622, 1448, 1402, 1336, 1167, 1113, 851; δH (400 MHz;
CDCl3) 13.08 (1 H, s), 7.66-7.63 (4 H, m), 7.42-7.35 (6 H, m),
6.52 (1 H, s), 6.05 (1 H, s), 5.84 (1 H, t, J = 5.6), 4.71 (2 H, s), 4.07
(2 H, s), 3.53 (2 H, d, J = 5.6), 2.36 (3 H, s), 1.05 (9 H, s); δC (100
MHz; CDCl3) 182.8 (C), 167.0 (C), 164.7 (C), 158.1 (C), 155.8
(C), 137.1 (C), 135.5 (CH), 133.2 (C), 129.7 (CH), 127.7 (CH),
123.5 (CH), 116.1 (C), 108.7 (CH), 106.6 (C), 99.2 (CH), 71.0
(CH2), 66.2 (CH2), 26.8 (Me), 21.0 (CH2), 20.5 (Me), 19.2 (C);
HRMS calcd for C31H32O5Si þ Naþ 535.1911, found MNaþ
535.1891.
5-Hydroxy-8-hydroxymethyl-2-methyl-6,9-dihydro-4H-oxepino-
[3,2-g]chromen-4-one (Ptaeroxylinol, 9). To a solution of the above
silyl ether (39 mg, 0.076 mmol) in THF (0.4 mL) was added tetra-n-
butylammonium fluoride solution (1 M in THF; 84 μL, 0.084
mmol) dropwise at 0 °C under argon. After 1 h at 5 °C, the mixture
was diluted with ethyl acetate (3 mL) and washed with a saturated
aqueous ammonium chloride solution (2 mL) and brine (2 mL).
The organic layer was dried over magnesium sulfate and evapo-
rated in vacuo, and the resulting oil was purified by chromatogra-
phy (light petroleum/ethyl acetate, 1:1) to give the title compound
(13 mg, 65%) as colorless crystals: mp 140-142 °C (lit.16 mp 135
°C; lit.28 mp 145 °C); νmax (CHCl3)/cm-1 3690, 3605, 3009, 2928,
1655, 1627, 1594, 1449, 1407, 1274, 1157, 1083, 850; δH (400 MHz;
CDCl3) 13.06 (1 H, s), 6.51 (1 H, s), 6.03 (1 H, s), 5.99 (1 H, t, J =
5.0), 4.74 (2 H, s), 4.04 (2 H, d, J = 5.4), 3.57 (2 H, d, J = 5.0), 2.35
(3 H, s), 1.51 (1 H, t, J = 5.4); δC (100 MHz; CDCl3) 182.8 (C),
167.2 (C), 164.6 (C), 158.1 (C), 155.8 (C), 138.0 (C), 125.3 (CH),
9-(tert-Butyldiphenylsilyloxy)methyl-5-hydroxy-2-methyl-8,11-
dihydro-4H-oxepino[2,3-h]chromen-4-one. To a solution of diene
19 (68 mg, 0.126 mmol) in distilled dichloromethane (63 mL) was
added [1,3-bis(2,4,6-trimethylphenyl)-2-imidazolidinylidene](tri-
cyclohexylphosphine)benzylideneruthenium(IV) dichloride
(Grubbs’ II catalyst) (11 mg, 0.013) in one portion under argon.
The reaction mixture was heated at 45 °C for 2.5 h and evaporated
after cooling. The resulting oil was purified by chromatography
(light petroleum/ether, 7:3) to give the stating material (14 mg)
and the title compound (50 mg, 98% based on recovered start-
ing material) as a colorless oil: νmax (CHCl3)/cm-1 3690, 3011,
2932, 2859, 1660, 1598, 1488, 1419, 1269, 1189, 1159, 1105,
J. Org. Chem. Vol. 75, No. 2, 2010 357