反应详情

To a stirred suspension of sodium hydride (0.75, 31.4 mmol) in N,N-dimethylimidazolidinone (10 ml) was added 3,4,5-trimethoxy-benzyl-phosphonium bromide (8.26 g 15.71 mmol) under argon. The aldehyde (4.0 g, 1258 mmol) from Example 40 was added to the deep red solution followed by 2 ml of N,N-dimethylimidazolidinone. Before adding ice (10 g)-water (75 ml) the mixture was stirred overnight. Upon extraction with ethyl acetate (3×100 ml), the organic phase was washed with water (3×75 ml), dried and evaporated to a dark colored mass (9.0 g). The crude product in hexane-ethyl acetate (9:1) was chromatographed on a column of SILICA GEL (200 g) to afford a mixture of E- and Z-isomers (3.70 g, 61% yield). A 1.1 g sample of the mixture was rechromatographed on a column of SILICA GEL and eluted with hexane-ethyl acetate (19:1) to furnish Z-isomer (0.25 g) and E-isomer (0.32 g). The Z-isomer was further purified by preparative TLC (hexane-ethyl acetate, 7:3) to yield 3', 4'-Dibenzyloxy-3,4,5-trimethoxy-(Z)-stilbene as a chromatographically homogeneous and viscous oil: IR νmax 1581, 1509, 1462, 1454, 1412, 1265, 1237, 1128, 1007 cm-1 ; 1H-NMR (400 MHz) 3.731 (6H, s, 2×OCH3), 3.856 (3H, s, OCH3), 4.856 (2H, s, ArCH2), 5.121 (2H, s, ARCH2), 6.589 (2H, s, ArH), 6.600 (3H, m, ArH), 6.747 (1H, d, J=8.6 Hz, ArH), 6.758 (1H, brs, ArH), 7,273-7,407 (10H, ArH).

1. extractionUpon extraction with ethyl acetate (3×100 ml)
2. washthe organic phase was washed with water (3×75 ml)
3. customdried
4. customevaporated to a dark colored mass (9.0 g)
5. customThe crude product in hexane-ethyl acetate (9:1) was chromatographed on a column of SILICA GEL (200 g)
6. customto afford
7. additiona mixture of E- and Z-isomers (3.70 g, 61% yield)
8. customA 1.1 g sample of the mixture was rechromatographed on a column of SILICA GEL
9. washeluted with hexane-ethyl acetate (19:1)
10. customto furnish Z-isomer (0.25 g) and E-isomer (0.32 g)
11. customThe Z-isomer was further purified by preparative TLC (hexane-ethyl acetate, 7:3)