Improved Methodology for the Preparation of Chiral Amines

catalysts for reductive amination in 1974. He tested rhodium and cobalt based catalysts for
the reductive alkylation of ammonia and aniline derivatives. He found that the activity of
cobalt catalyst is highly influenced by the structure of phosphine ligand. Also he recognized
that using basic aliphatic amines led to poising of the cobalt catalyst and no product was
formed. On the other hand rhodium was used successfully in the reductive amination of these
basic amines. [13] Despite these interesting results the reaction conditions were harsh (100–300
bar H 2 , 110–200 °C) and no turnover number were reported. In 2000, Börner described more
practical system for homogenous reductive amination. [14] Benzaldehyde and piperidine could
be reductively aminated using [Rh(dppb)(COD)]BF 4 or [Rh(1,2-bisdiphenylphosphinitoethane)(COD)]BF
4 under milder conditions (50 bar H 2 , room
temperature) with 500 TON (scheme 3.3).
O
H
H
N
0.2% Rh cat
H 2 (50 bar)
rt,