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Catalytic Hydrogenation of Nitrostyrenes


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5% Palladium on charcoal (K-type), 1 atm H2 [1]

As a typical example, the preparation of 3,4-methylenedioxy-beta-phenethylamine is described. In a 30-mL side-arm flask equipped with a magnetic stirring bar were placed 3,4-methylenedioxy-beta-nitrostyrene (0.500 g, 2.59 mmol), 5% palladium on charcoal (K-type) (0.533g, Pd 0.26 mmol), 12 M HCl (0.5 mL), and ethanol (10 mL). The reaction mixture was stirred at 0C for 3 h under a hydrogen atmosphere (1 atm). The catalyst was removed by filtration through celite and the solution washed with CH2Cl2 (3x20 mL). The aqueous layer was neutralized with aqueous ammonia solution (28%, 5 mL) and extracted with CH2Cl2 (4x20 mL). The combined organic layers was dried over Na2SO4. Evaporation of the solvent gave 0.303 g of product, or 71%.

The yield for mescaline was 65%.


Palladium Black, 1 atm H2 [2]

Suspension of 3 g. 3-methoxy-4,5-dioxy-omega-nitrostyrene in 80 ml AcOH with simultaneous introduction of H2 was added to vigorously shaken mixture of 3 g. Pd black in 65 ml AcOH and 2 ml konc. H2SO4, previously saturated with H2 during 30 min. When absorption calculated amount of H2 finished, catalyst was filtered off, AcOH removed in vacuo, and resulting oil cooled until starting of crystallisation. Deposited crystals filtered and washed directly on the filter with 15 ml acetone. Yield of amine bisulphate is 2 g (52%), mp107-108C (from water).


Palladium Black, 1 atm H2 [3]

Suspension of 15 g. Pd black in 175 ml AcOH was saturated with H2 under vigorous shaking during 30 min. Then 7.5 ml of conc H2SO4 (d=1.84) in 25 ml of AcOH was added and saturation with H2 was continued at another 15 min. After saturation of catalyst, with simulaneous introduction of H2, was added suspension of 25 g. 2-hydroxy-3-methoxy-omega-nitrostyrene in 75 ml AcOH in little portions during 3 hrs. After absorption of calculated amount H2 - reaction complete. From filtrate after removing Pd solvent was distilled off, crystalline residue treated with 50 ml of AcOEt and filtered. Sulphate was dissolved in minimum quantities of water (25 ml), and basefied with aq. NH3, deposited base was filtered off and air-dried. Yield of 2-oxy-3- methoxy-phenethylamine 16.4 g. (76%), mp 112C.


References

[1] Bull. Chem. Soc. Jpn., 63, 1252-1254 (1990)
[2] Zh. Org. Khim. 32, p. 2661 (1962)
[3] Zh. Org. Khim. 35, p. 720 (1965)