Reaction #1935

Reaction equation

benzyl bromide

lithium diisopropylamide

ether

4-cyanopiperidine

THF

→

expected product

1,4-Dibenzyl-4-cyanopiperidine

Solvents

cyclohexane

Conditions

Workup

1. 1
   workup.STIRRINGthe mixture is stirred for 3 hours after the temperature
2. 2
   Otherto rise to RT
3. 3
   workup.ADDITIONis added
4. 4
   Otherthe precipitate formed
5. 5
   Filtrationis filtered off
6. 6
   Washwashed with water
7. 7
   workup.ADDITIONby the addition of concentrated NaOH solution
8. 8
   Extractionextracted with ether
9. 9
   Dryingthe organic phase is dried over MgSO4
10. 10
    Otherthe solvent is evaporated off

Procedure

A solution of 15 g of 4-cyanopiperidine in 250 ml of THF is cooled to -50° C., 190 ml of a 1.5M solution of lithium diisopropylamide in cyclohexane are added dropwise and the mixture is stirred for 30 minutes at -50° C. 34 ml of benzyl bromide are then added and the mixture is stirred for 3 hours after the temperature has been allowed to rise to RT. The reaction mixture is poured into an ice/concentrated HCl mixture, ether is added and the precipitate formed is filtered off and washed with water. The precipitate is taken up with water, rendered alkaline to pH 12 by the addition of concentrated NaOH solution, and extracted with ether, the organic phase is dried over MgSO4 and the solvent is evaporated off to give 31.7 g of the expected product after crystallization from pentane. M.p.=92° C.

Source