Dextroamphetamine synthesis from P2P by (S)-(−)-α-Methylbenzylamine

WillD

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Reagents:
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  • Phenylacetone (cas 103-79-7) 1000 g;
  • (S)-(−)-α-Methylbenzylamine (cas 2627-86-3) 904 g;
  • Sodium borhydride 282 g;
  • Boric acid (H3BO3) 461 g (or p-toluenesulfonic acid monohydrate 1418 g, or benzoic acid 911 g);
  • Sodium bicarbonate (NaHCO3);
  • Dichloromethane (CH2Cl2) (or ether, or petroleum ether) 2100 ml;
  • Sodium sulphate (Na2SO4) anhydrous;
  • Formic acid 1026 g;
  • Potassium hydroxide (KOH) 1251 g;
  • Ethanol (EtOH) L;
  • Palladium on carbon (Pd/C 10%) 475 g;
  • Acetone 3 L;
  • Sulfuric acid (H2SO4 98%) concentrated ~750 ml;

Equipment and glassware:
  • 5 L Round bottom flask;
  • Top stirrer and heating plate;
  • Water bath;
  • Glass rod and spatula;
  • Rotovap machine (optional);
  • Laboratory scale (1-1000 g is suitable);
  • Measuring cylinders 100 and 500 mL;
  • 1000 mL x3; 2000 mL x3; 500 mL x3 Beakers;
  • 5 L Separatory funnel;
  • Boiling chips;
  • Buchner flask and funnel [Schott filter may be used for small quantities];
  • Pasteur pipette;
  • Freezer;
  • Vacuum desiccator (optional);

Step 1. Phenylacetone (P2P) reductive amination.
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1. Phenylacetone 1000 g and (S)-(−)-α-Methylbenzylamine 904 g are put into a 5 L round bottom flask;
2. The mixture is stirred at room temperature for 10-15 min;
3. Sodium borhydride 282 g is added slowly in several portions to the reaction mixture;
4. Then, boric acid (H3BO3) 461 g is added. It can be replaced by p-toluenesulfonic acid monohydrate 1418 g or benzoic acid 911 g;
5. The reaction mixture is stirred for 1 h at room temperature;
6. Next, the mixture is quenched with sodium bicarbonate (NaHCO3) saturated aqueous solution to
alkaline pH 11-12;
7. Alkaline solution is
extracted with dichloromethane (CH2Cl2) (or ether, or petroleum ether) 700 ml x3 in separatory funnel;
8. Extract is dried over anhydrous
sodium sulphate (Na2SO4), filtered and concentrated under vacuum (optional) to get N-benzylamphetamine free base;

Step 2. Benzyl group removing from N-benzylamphetamine (debenzylation).
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1. Formic acid 1026 g, potassium hydroxide (KOH) 1251 g, N-benzylamphetamine free base 1000 g and ethanol (EtOH) 5 l are added into a 20 L flask, which is equipped with reflux condenser.
2. The reaction mixture is heated to a reflux temperature.
3. Palladium on carbon Pd/C 10% 475 g catalyst is added to the heated reaction mixture.
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Pd/C catalyst
4. The mixture is stirred at reflux temperature for 60 min.
5. The mixture is cooled to room temperature and filtered after reaction procedure.
6. Ethanol solution is evaporated
under vacuum (optional) to get dextroamphetamine free base oil.
7. The catalyst powder is collected on the filter, washed with distilled water twice and washed with ethanol once.
8. An isolated catalyst is dried and used in a next batch.


Step 3. Dextroamphetamine sulphate preparation.
1. Amphetamine free base from Step 2.6 is dissolved in acetone 2 l and stirred well.
2. Sulfuric acid (H2SO4) is added dropwise to
reach pH 6.
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3. The mixture is put into a freezer for 12 h.
4. After that, the mixture is
filtered and washed on a Buchner filter with cold acetone and dried on air or in vacuum desiccator to get Dextroamphetamine sulfate powder.
 
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Mr.Blanks00

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hello sir, what is the percentage of the purity of the dextroamphetamine product for this method.
 

TotalSynthesis

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ooh, that's a good one, didnt know it. i can directly source (S)-(−)-α-Methylbenzylamine quite easily.

@William Dampier how can this way be adopted to produce d-meth, do you maybe know that?

thx
 

G.Patton

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Hello, unfortunately no. You can use l- or d-tartaric acid for d-meth. Look at here. Procedure is the same, also read comment section.
 

cokemuffin

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It just depends on the purity of your methylbenzylamine
 

cokemuffin

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Only way i could think of is to go from dexamphetamine to dexmethamphetamin via formaldehyde
 

G.Patton

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Hi, you'll get racemic mixture from this way.
 

cokemuffin

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Oh sry didn't know that, does the same apply to fenethyline?
 

G.Patton

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I think yes, it is Nucleophilic substitution reaction, which gives racemic product.

Edit: stereoselective reductive alkylation into d-meth
 
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OrgUnikum

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It is a reductive amination also called reductive alkylation with the formaldehyde being the alkyl. There is no inversion or razemisation so Dextro-Amphetamine will yield Dextro-Methamphetamine when reductivly alkylated with formaldehyde.
 

G.Patton

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You are right, thank you for your note.
 

TotalSynthesis

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@G.Patton

using a cheaper catalyst should be possible. What would you expect which one could be a good substitution?
Raney?
Ni/C?
 

G.Patton

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I guess Ni/Re but I'm not 100% sure.
 

ossi

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if raney-nickel would work, what will be different?
quality? purity? yield?
 
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G.Patton

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Probably yield. About what quality are you asking me? Pure amphetamine racemate always have same effects.
 

ossi

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i thought the quality of the catalyst might change the quality of the product.
how high do you estimate the probability that raney-nickel works?
 

G.Patton

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In this synthesis catalyst effect on hydration completeness and speed it up.
 

ossi

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thank you very much
 

ossi

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it’s very expensive, how often can i use this?
 

Davidrobinson

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What is the yield of this reaction
 

mygodson

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The amount of pd/c is much too many。
 
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