2,3-Diamino-4,5-diarylcyclopentadienone iron carbonyl complexes as catalysts for reductive amination reactions

The reaction of dipiperidinoacetylene, (CH 2 ) 5 NCCN(CH 2 ) 5 , with a series of 2,3-diarylcyclopropenones (Ar) 2 C 3 O (Ar = phenyl, 4- tert -butylphenyl, 2,5-dimethylphenyl, 4-trifluoromethylphenyl) afforded 2,3-dipiperidino-4,5-diarylcyclopentadienones, which were used to prepare cyclopentadienone (CPD) iron tricarbonyl complexes [(CPD)Fe(CO) 3 ] by the reaction with Fe 2 (CO) 9 . Subsequent treatment with trimethylamine- N -oxide in the presence of acetonitrile afforded the corresponding acetonitrile complexes [(CPD)Fe(CO) 2 (NCCH 3 )], which were used as catalysts for the reductive amination of citronellal with various secondary amines under 5 bar of dihydrogen pressure. The first iron-catalysed reductive amination for the preparation of the pharmaceutically important antidepressant sertraline is also reported.