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A Biphasic Medium Slows Down the Transfer Hydrogenation and Allows a Selective Catalytic Deuterium Labeling of Amines from Imines Mediated by a Ru−H/D + Exchange in D 2 O
Author(s) -
RuizCastañeda Margarita,
Carrión M. Carmen,
Santos Lucía,
Manzano Blanca R.,
Espino Gustavo,
Jalón Félix A.
Publication year - 2018
Publication title -
chemcatchem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.497
H-Index - 106
eISSN - 1867-3899
pISSN - 1867-3880
DOI - 10.1002/cctc.201801343
Subject(s) - chemistry , transfer hydrogenation , reductive amination , imine , toluene , aldehyde , hydride , deuterium , selectivity , catalysis , amine gas treating , aldimine , medicinal chemistry , organic chemistry , ruthenium , hydrogen , physics , quantum mechanics
The transfer hydrogenation (TH) of several aldimines has been studied using [RuCl( p ‐cymene)(dmbpy)]BF 4 , 1 , (dmbpy=4,4′‐dimethyl‐2,2′‐bipyridine) as a precatalyst. Both neat water and a biphasic water/toluene mixture (w/t) have been successfully used as solvents. In the w/t medium the corresponding precursors, amine and aldehyde, were also used as substrates for a transfer hydrogenative reductive amination. Selective deuterium labeling of the resulting alkylated amines was the main goal of this work. On using D 2 O the D‐content in the amine was negligible but a high level of D‐incorporation was achieved in D 2 O/toluene. According to calculations, this is due to the effect of the relative rates of the hydride transfer and that of the RuH/D + exchange. The incorporation of deuterium increases with time as a consequence of the reduction in the hydride transfer rate as the substrate concentration diminishes. The recyclability assays performed reflect the importance of pH in the selectivity of the TH towards the imine or the aldehyde resulting from imine hydrolysis.