Phenylpropanolamine and Cathinone from Propiophenone

Introduction

The operation must be carried out outside or under a fume hood. Safety goggles and protecting glasses are a must. Do not get in contact with the intermediate, alpha-bromopropiophenone, which is a lachrymator and very irritating.

alpha-Bromopropiophenone

In a 2000 two-necked round-bottom-flask with dropping funnel and reflux condenser, dissolve 1 mole (134.2 g) propiophenone in 250 mL glacial acetic acid. Cool the mixture in an ice-bath, and add over a period of an hour 1.05 moles of bromine (168 g; 53.5 mL) in 150 mL glacial acetic acid with stirring, the temperature in the mixture should be at 10-20°C. After the hour, heat on the water bath with stirring, bath temperature 50 deg Celsius, for 4 hrs, and evaporate the volatiles by vacuum distillation. The residue is an oil, alpha-bromopropiophenone, which is used directly without purification. The product is kept in this flask.

Cathinone

Saturate 800 mL alcohol (95 %) with ammonia (generated from sodium hydroxide and ammonia solution), 100 g should be in the solution (so saturate the alcohol until its weight is 100 g higher). Add the alcoholic ammonia to the flask with the alpha-bromopropiophenone, carefully, with stirring, using a reflux condenser and a dropping funnel. Stirr for 2 hrs at 20°C and then for 6 hrs. at 60°C to get 2-amino-1-phenyl-1-propanone. The solution is concentrated to dryness at the rotary evaporator, and water/ammonia solution (1:1, 500 mL) is added. Add 50 gr. table salt to reduce the solubility of the product, extract the product four times with 400 mL methyl tert-butyl ether, and evaporate the extract (no drying) at the rotary evaporator.

Phenylpropanolamine (PPA)

Dissolve the residue in 500 mL THF/2-propanol (1:1 by volume), (two-necked round bottom flask 2000 mL, condenser, one neck with stopper), and add finely powdered sodium borohydride (NaBH4),40 g, in small portions. Stir for 24 hrs, and add acetic acid + water until the bubbling (borane, hydrogen) (do not breathe! borane is deadly poisonous). Add then hydrochloric acid to pH 1, evaporate all volatiles in vacuum to dryness at the rotary evaporator, and add 50% sodium hydroxide (200 mL), table salt (100 g). Extract your product with 4x400 mL methyl tert-butyl ether, dry over sodium sulfate, and evaporate the solvent at the rotary evaporator. The residue is fairly pure PPA (racemic), which can be distilled in vacuum. The product crystallizes on standing, melting at 52-53°C.

For reduction to DL-amphetamine, vacuum distillation is not is not necessary until you use hydrogen and catalyst. The yield of product is about 100 g.