(Chief Bee)
03-13-03 15:59
No 416740
      Novel amino acid decarboxylation via the nitrile
(Rated as: excellent)

This procedure should also be applicable to turn Tryptophan into Tryptamine, with Indole-3-acetonitrile as intermediate.

Phenylalanine to Phenethylamine via Phenylacetonitrile

l-Phenylalanine (400 mg, 2.42 mmol) was taken up in a mixture of EtOH (40 mL), H2O (2 mL) and a sat. aq solution of NH4Cl (1.5 mL). To the stirred amino acid solution was added NBS (1.07 g, 6.05 mmol) in DMF (5 mL) at r.t., whereupon CO2 was evolved immediately. After 20 min, nickel(II) dichloride hexahydrate (2.30 g, 9.68 mmol) was dissolved into the reaction mixture and NaBH4 (915 mg, 24.2 mmol) was added in portions with vigorous stirring. Addition of the latter was exothermic and hydrogen was vigorously evolved. After 30 min at r.t., the reaction was filtered through Celite®, and the ethanol was removed. The liquid residue was taken up in water (20 mL) and basified to pH 10 with aq 1.0 M NaOH. The aq solution was extracted with Et2O (2 × 30 mL). The combined organic extracts were washed with a sat. aq solution of NaHCO3 (20 mL) and dried over MgSO4. Removal of the solvent afforded 2-phenylethylamine (9a) (208 mg, 71%) as a colourless oil.

Synlett 542-546 (2003) (../rhodium/pdf /aminoacid.decarboxylation.pdf)