REDUCTION OF WEINREB AMIDE TO ALDEHYDE




REDUCTION OF WEINREB AMIDE TO ALDEHYDE

Using LAH


 



 

F SM/Reagent

F Eq

F Apparatus

Weinreb Amide (FW: 187.28)

1.0

Multi Neck Flask

LAH (1M in Et2O)

1.5

Stirrer

Et2O (Anhy)

3ml/1mmol SM

Cold bath

 

 

 

 



 

Procedure

 

1.    Dissolve Weinreb Amide in Et2O.  Stir.  Cool to 0 oC

2.    Add LAH/Et2O [1]

3.    Stir the mixture at 0 oC for 1 hr [2]

4.    Quench slowly w/sat aq. KHSO4 [3]

5.    Warm to R.T.  Stir for 30 min

6.    Add 1N HCl and stir for 2 hrs [4] ® separate

7.    Wash organic layer w/sat NaHCO3 then water and brine

8.    Dry w/MgSO4.  Filter

9.    Concentrate in vacuo  [5]® crude as colorless liquid

10.           NMR w/CDCl3.  Yield >95% [6]



Notes:

[1]   Inside temp: < 0 oC during addition.  ¯  white appear

[2]   Follow reaction by TLC w/10% EtOAc/Hex (I2 or KMnO4)

[3]   Gas ­ , D ­

[4]   More ¯ white appear

[5]  Rotovac bath temperature: 40 oC

[6]  No further purification