反应详情

5-Bromo-1-triisopropylsilylindole (2.0 g, 5.68 mmol) was dissolved in THF (dry, 30 mL) and the solution cooled to -70° C. tert-Butyllithium (1.7M in hexane; 10.7 mL, 18.2 mmol) was added, and by the time addition was complete, a permanent yellow coloration had been produced. After a further 1 hr at -65° C. benzaldehyde (0.658 g, 6.20 mmol) was added and the mixture stirred at ca -65° C. for 1 hr before warming gradually to room temperature H2O and NaCl were added to the mixture which was then extracted (3×) with Et2O, and the extracts were combined, washed (H2O, 3× and then saturated aqueous NaCl) and dried (MgSO4). Evaporation gave a gum which was chromatographed (silica gel; hexane/Et2O; 0-30%). Recovered starting material, 0.437 g (22%) eluted first; followed by the product: phenyl(1-triisopropylsilylindol-5-yl)methanol, a gum which solidified on standing, 0.61 g (28%; several fractions containing contaminated product were subsequently obtained). The pure product (0.6 g, 1.58 mmol) was dissolved in THF (10 mL) and treated with tetra-n-butylammonium fluoride solution (1.0M in THF; 3.0 mL) at room temperature. The mixture was stirred for 1.5 hr and then partitioned between Et2O and saturated aqueous NaCl. After re-extracting the aqueous layer (Et2O; 2×), the combined ethereal layers were washed with saturated aqueous NaCl, dried (MgSO4) and evaporated to a gum which was chromatographed (silica gel; hexane/Et2O; 0-50%), giving: phenyl(indol-5-yl)methanol, as an almost colourless gum, 0.347 g (98%). This material was hydrogenated in EtOH (25 mL) over Pd-C (5%; a total of 0.30 g was added over the reaction period, in two portions), at 45 psi, for ca 40 hr. The catalyst was filtered off, and the filtrate evaporated to a gum which was chromatographed (silica gel; hexane/Et2O; 0-50%). The required product: 5-benzylindole, was obtained as an off white solid, 0.135 g (44%), as well as 5-benzylindoline 0.03 g, (10%) and unreacted starting material, 0.013 g (4%).

1. additionwas added
2. additionby the time addition
3. customa permanent yellow coloration had been produced
4. additionwere added to the mixture which
5. extractionwas then extracted (3×) with Et2O
6. washwashed (H2O, 3×
7. dry with materialsaturated aqueous NaCl) and dried (MgSO4)
8. customEvaporation
9. customgave a gum which
10. customwas chromatographed (silica gel; hexane/Et2O; 0-30%)
11. customRecovered
12. washeluted first
13. additionseveral fractions containing contaminated product
14. customwere subsequently obtained)
15. stirringThe mixture was stirred for 1.5 hr
16. custompartitioned between Et2O and saturated aqueous NaCl
17. extractionAfter re-extracting the aqueous layer (Et2O; 2×)
18. washthe combined ethereal layers were washed with saturated aqueous NaCl
19. dry with materialdried (MgSO4)
20. customevaporated to a gum which
21. customwas chromatographed (silica gel; hexane/Et2O; 0-50%)
22. customgiving
23. additiona total of 0.30 g was added over the reaction period, in two portions), at 45 psi
24. waitfor ca 40 hr
25. filtrationThe catalyst was filtered off
26. customthe filtrate evaporated to a gum which
27. customwas chromatographed (silica gel; hexane/Et2O; 0-50%)