反应详情

Lithium hexamethyldisilazane (180 mL, 0.18 mol, 1 M in tetrahydrofuran) under nitrogen was cooled to not more than 5° C. with a ice bath. A solution of 1-benzyl-piperidine-4-carboxylic acid ethyl ester from Example 7B (40.0 g, 0.16 mol) in tetrahydrofuran (450 mL) was added at such a rate as to keep the internal temperature at not more than 5° C., and the mixture was stirred at not more than 5° C. for 1 hour. A solution of formaldehyde O-benzyl-oxime from Example 7A (20.0 g, 0.15 mol) in tetrahydrofuran (200 mL) was added, and the reaction mixture stirred at not more than 5° C. for 1 hour. A saturated aqueous solution of NH4Cl (300 mL) was added, and the layers were separated. The aqueous layer was extracted with ethyl acetate (500 mL). The combined organic layers were washed with brine (300 mL), dried over Na2SO4, filtered and concentrated in vacuo. The resulting residue was purified by flash chromatography on silica gel (300 g) eluting with hexane/ethyl acetate (4:1 to 1:1) to afford the titled compound. 1H NMR (400 MHz, CDCl3) δ ppm 1.54-1.63 (m, 2 H) 1.91 (ddd, J=13.17, 9.47, 3.70 Hz, 2 H) 2.03-2.17 (m, 2 H) 2.68-2.77 (m, 2 H) 3.03 (s, 2 H) 3.45 (s, 2 H) 4.93 (s, 2 H) 7.19-7.42 (m, 10 H).

1. customat not more than 5° C.
2. stirringthe reaction mixture stirred at not more than 5° C. for 1 hour
3. customthe layers were separated
4. extractionThe aqueous layer was extracted with ethyl acetate (500 mL)
5. washThe combined organic layers were washed with brine (300 mL)
6. dry with materialdried over Na2SO4
7. filtrationfiltered
8. concentrationconcentrated in vacuo
9. customThe resulting residue was purified by flash chromatography on silica gel (300 g)
10. washeluting with hexane/ethyl acetate (4:1 to 1:1)