Amphetamine synthesis via 1-phenyl-2-nitropropene LAH reduction

[WillD]

Reagents:

• Lithium aluminum hydride (LAH; cas 16853-85-3) 12 g;
• 1,4-Dioxane 300 ml;
• 1-Phenyl-2-nitropropene (P2NP; cas 705-60-2) 10 g;
• Sodium hydroxide (25% NaOH) aq. solution;
• Acetone ~50 ml;
• Sulfuric acid ~10 ml;

Equipment and glassware:

• Two-naked round bottom flask 1 L;​
• Retort stand and clamp for securing apparatus;​
• Magnetic or top stirrer;​
• Beakers 200 ml x3;​
• Drip funnel;​
• pH Indicator paper;​
• Laboratory scale (0.1-200 g is suitable);​
• Measuring cylinder 100 mL;​
• Reflux condenser;​
• Vacuum source;​
• Glass rod and spatula;​
• Rotovap machine (optional);​
• Water bath with ice;​
• Funnel;​
• Filter paper;​
• Buchner flask and funnel;​
• Freezer;​

Reaction scheme:

​

Synthesis:

1. Lithium aluminum hydride (LAH) 12 g is weighted and put into a 1 L two-naked round bottom flask.
2. 1,4-Dioxane 200 ml is added into the flask.
3. The flask is places onto a magnetic stirrer and clamped on a retort stand, stirring bar is placed into the flask.
4. 1-Phenyl-2-nitropropene (P2NP) 10 g and 1,4-dioxane 100 ml are mixed in a 200 mL beaker. The mixture is stirred at room temperature until 1-Phenyl-2-nitropropene (P2NP) is dissolved.
5. A drip funnel is installed onto a reaction flask neck. The P2NP solution from step 4 is poured into the drip funnel.
6. A drip funnel tap is opened and solution from step 4 is poured dropwise into the reaction mixture.
7. The reaction mixture is stirred at room temperature for 30 min after complete P2NP solution addition.
8. Reflux condenser is installed onto the flask and the reaction mixture is refluxed for 1 h.
9. Then, the reaction flask is cooled in an ice water bath.
10. LAH is decomposed by the slow sodium hydroxide (25% NaOH aq. solution) addition.
11. The resulting white suspension is filtered from solids. Organic layer is separated with help of separatory funnel.
12. Organic layer is evaporated under reduced pressure. Amphetamine free base yellow oil is obtained.
13. The amphetamine free base oil is dissolved in x3 acetone volume.
14. Sulfuric (or orthophosphoric) acid is added dropwise with a constant stirring to reach pH 6.
15. The mixture is put into a freezer for 12 hours.
16. Next, the mixture is filtered on a Buchner flask and funnel. Amphetamine sulphate salt is air dried or dried in a vacuum desiccator.​

 

[Hans-Dietrich]

It is a bad idea to add dioxane to the LAH in the flask. Will not end well.

 

[G.Patton]

Lithium aluminum hydride dissolves well in ether (35g/100ml) and hardly dissolves in dioxane (0.1g/100ml). If you have absolutely dry dioxane nothing will happen. It has violent reaction with water (trace will enough). I think dioxane was used here cuz it is easier to find than ether. You may try to substitute dioxate by THF, cuz it better solves LAH (13g/100ml).

 

[Hans-Dietrich]

This should be very very dry dioxane in a very dry environment. It is necessary to add LAH to the dioxane and not vice versa. Otherwise, there will be a little boom ... It makes sense to use dried Et2O as Shulgin did, yes or THF.

 

[ymaaah]

ether, you mean ethyl ether? ethyl ether is very dangerous, but acetate ether is better no? So if you use dioxane because ethyl ether is very inflammable and dangerous, acetate ether is a good way, or you use dioxane for another reason?

 

[yuiopjkl]

I've seen a video about this synthesis before, but it was in Russian

If you are interested let me know and I will look for it

 

[T 3]

What about using Red-Al and would u use same amounts as would LAH or..? Thx

 

[WillD]

It is advisable to use a greater excess by weight, so the replacement is not very convenient.