Trifluoroacetic acid → 4-(3-phenylpropylidene)Piperidine-

Temperature

0 °C

n-Butyl lithium (2.5M in hexanes, 14 ml, 35 mmol) was carefully added to a cold (<0° C.) suspension of 3-phenylpropyltriphenylphosphonium bromide (18.7 g, 40.5 mmol) in THF (100 ml) under a nitrogen atmosphere at such a rate that the temperature did not exceed 0° C. The orange solution was stirred at <0° C. for 30 minutes before a solution of 1-(tert-butyloxycarbonyl)-4-piperidone (5.0 g, 27 mmol) was added as a solution in THF (20 ml) at such a rate that the temperature did not exceed 0° C. The mixture was stirred at 0° C. for 1 hour and then allowed to warm to room temperature before adding water (20 ml). The mixture was concentrated in vacuo and the residue extracted into dichloromethane (3×100 ml). The combined organics were washed with water (20 ml) and brine (20 ml), dried (MgSO4) and evaporated in vacuo to give a yellow oil. The oil was purified by column chromatography on silica eluting with 10% EtOAc/petrol 60/80 to give a clear oil. The oil was dissolved in dichloromethane (30 ml) and treated with trifluoroacetic acid (20 ml) and the mixture stirred at room temperature for 1.5 h. The solution was evaporated in vacuo and azeotroped with toluene (2×10 ml). The residue was dissolved in EtOAc (20 ml) and washed with sodium carbonate (saturated, 2×10 ml), water (10 ml) and brine (10 ml), dried (MgSO4) and evaporated in vacuo to give 4-(3-phenylpropylidene) piperidine as a pale oily solid (4.92 g, 90%).

1. customdid not exceed 0° C
2. customdid not exceed 0° C
3. temperatureto warm to room temperature
4. concentrationThe mixture was concentrated in vacuo
5. extractionthe residue extracted into dichloromethane (3×100 ml)
6. washThe combined organics were washed with water (20 ml) and brine (20 ml)
7. dry with materialdried (MgSO4)
8. customevaporated in vacuo
9. customto give a yellow oil
10. customThe oil was purified by column chromatography on silica eluting with 10% EtOAc/petrol 60/80
11. customto give a clear oil
12. stirringthe mixture stirred at room temperature for 1.5 h
13. customThe solution was evaporated in vacuo
14. customazeotroped with toluene (2×10 ml)
15. dissolutionThe residue was dissolved in EtOAc (20 ml)
16. washwashed with sodium carbonate (saturated, 2×10 ml), water (10 ml) and brine (10 ml)
17. dry with materialdried (MgSO4)
18. customevaporated in vacuo

ORD record

ord-5fafef9fa8354ec99da281bc8ce69ed9

Source dataset

uspto-grants-1998_02

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US05714498