Ethyl 2-(2-nitroethyl)-1-benzylpyrrolidine-2-carboxylate → 1-Benzyl-1,7-diazaspiro[4.4]nonan-6-one

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Reaction Steps

Raney nickel (˜2 g) was added to a solution of ethyl 2-(2-nitroethyl)-1-benzylpyrrolidine-2-carboxylate (6.00 g, 19.6 mmol) in absolute ethanol (200 mL) in a hydrogenation bottle. The mixture was shaken for 12 h under a hydrogen atmosphere (50 psi) in a Parr hydrogenation apparatus, filtered through a Celite pad and concentrated by rotary evaporation. GCMS analysis indicated that the hydrogenation product was a mixture of the primary amine and the lactam resulting from cyclization of the amine onto the ester. The mixture was dissolved in toluene (150 mL). A catalytic amount of p-toluenesulfonic acid (˜30 mg) was added and the mixture was heated at reflux under a nitrogen atmosphere for 24 h. Upon evaporation of the toluene, the residue (now entirely lactam, by GCMS) crystallized to give 4.20 g (93.1%) of tan solid (mp 152-153° C.).

Provenance & Evidence