L-Ephedrine synthesis from L-phenylacetylcarbinol (L-PAC)

[btcboss2022]

Any option to replace the microwave by normal heating obviously changing temp and time?

 

[btcboss2022]

Any option to replace the microwave by normal heating obviously changing temp and time?

btcboss2022@G.Patton Won't be enough with a standard reductive amination of the L-PAC?
Ethanol + methylamine (40% in water) + L-PAC and left to react at room temperature for 30 min, to allow imine formation.
The mixture was cooled to around 0 C and reduced using NaBH4.
The mixture was then basified and extracted with DCM
Dried dried anhydrous sodium sulphate, filtered and evaporated.

 

[OrgUnikum]

@G.Patton Won't be enough with a standard reductive amination of the L-PAC?
Ethanol + methylamine (40% in water) + L-PAC and left to react at room temperature for 30 min, to allow imine formation.
The mixture was cooled to around 0 C and reduced using NaBH4.
The mixture was then basified and extracted with DCM
Dried dried anhydrous sodium sulphate, filtered and evaporated.

btcboss2022l-PAC is very sensitive to bases, they cause it to racemise what would be a pity. Acidic or neutral conditions are advised, with NaBH4 one can use use easily prepared derivates like STAB (from NaBH4 in Toluene with 3 equivalent GAA added) or Zinc-Borohydride (from anhydrous ZnCl2 and NaBH4) or others. No heating whatsoever is needed and water is no problem just add equimolar methylamine acetate to the l-PAC in Toluene add 0,01 molar tosic acid dihydrate and let it sit at rt for a day, this forms a stable Imine which is then reduced by STAB. Excellent yields. Avoids completely alkaline conditions. Only drawback is the amount of GAA needed - 4 equivalent

 

[The-Hive]

@Consider look here