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           Preparation of Phenylacetones from Phenyl-2-Nitropropenes
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1) Using NaBH4 + H2O2/K2CO3
2) Using Fe/Acetic Acid

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Preparation of Phenyl-2-Propanone (P2P) 
by Rhodium - as submitted to Total Synthesis II by Strike

In this preparation, phenyl-2-nitropropene is reduced to phenyl-2-nitropropane 
with sodium borohydride in methanol, followed by hydrolysis of the nitro group 
with hydrogen peroxide and potassium carbonate, a variety of the Nef reaction. 
The preparation is a one-pot synthesis, without isolation of the intermediate. 

Efforts directed to prepare MDP2P via this method results in good yields of a 
ketone with properties completely dissimilar to MDP2P, and is probably the 
propiophenone, formed by migration of the nitro group during the hydrolysis.

16.3g (0.1 mole) phenyl-2-nitropropene was dissolved in 200ml methanol in a 
250ml Erlenmeyer flask situated on a magnetic stirrer, and chilled to 0°C with 
an ice/salt bath. Then, with good stirring, 7.6g (0.2 mole) of NaBH4 was added a 
little at the time, and the temperature was not allowed to to rise above 15°C. 
When the generation of heat had subsided, the ice/salt- bath was removed and the 
solution was stirred at room temperature for two hours. At the end of this 
period, the flask was once again placed in an ice/salt bath and the solution was 
allowed to cool to 0°C again. 100 ml of 30% H2O2 was then added, together with 
30 grams of anhydrous potassium carbonate, and the solution was left to stir for 
18-24 hours at room temp. During the addition of H2O2/K2CO3 a white, sticky 
precipitate forms, which can be a bit too thick for a weak magnetic stirrer to 
handle, so the mass can be stirred with a glass rod now and then during the 
first two hours, after which the precipitate will be much looser and no match 
for any mag-stirrer. The next day, the solution is slowly acidified with 2M HCl 
with good stirring, care being taken for the evolution of heat and CO2. About 
300 ml of acid is needed. When the pH of the solution turned acid, the color 
became significantly more yellow, but the acidity was confirmed with pH paper. 
All of the precipitate was also be gone at this point. The solution was 
extracted with 3x100ml CH2Cl2, and the pooled organic extracts washed with 100ml 
2M NaOH and 200ml H2O. The organic phase was dried over MgSO4, filtered with 
suction, and the solvent removed under vacuum to give a clear yellow oil. After 
distillation of said oil at aspirator vacuum, the yield was around 60-70% of 
phenyl-2-propanone (P2P) as a light yellow oil.

Ref: R. Ballini, Synthesis 723-726 (1994)

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4-Methoxy-Phenyl-2-Propanone

4-Methoxy-Phenyl-2-Nitropropene (10 g, 51 mmol) was dissolved in 75 ml HOAc and 
slowly dripped into a refluxing slurry of Fe powder (32 g, 0.57 mol) in 140 ml 
HOAc. The mixture first turned brownish, and then white and foamy, and the 
mixture was refluxed on low heat for 1.5 h. The reaction mixture was poured into 
2000ml water, and was extracted with 3x100 ml CH2Cl2. The combined extracts was 
washed with 2x150 ml H2O and dried over MgSO4. The solvent was distilled off at 
atmospherical pressure, and the residue distilled under vacuum to give 6.1g 
(37 mmol, 72%) of an orange-pink oil at 110°C at 3mmHg.

Ref: Shulgin & Shulgin, Pihkal, #109

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