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Chemoselective Reduction of Imines Catalyzed by Ruthenium(II) Half‐Sandwich Complexes: A Mechanistic Study
Author(s) -
Reshi Noor U. Din,
Kathuria Lakshay,
Samuelson Ashoka G.
Publication year - 2019
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201900455
Subject(s) - chemistry , ruthenium , catalysis , silylation , dissociation (chemistry) , yield (engineering) , reaction mechanism , mass spectrometry , silane , silanes , reaction intermediate , combinatorial chemistry , photochemistry , medicinal chemistry , organic chemistry , materials science , chromatography , metallurgy
Ruthenium half‐sandwich complexes ligated to chiral 2‐oxazolidinethiones or 2‐thiozolidinethiones in the reduction of N‐benzylideneaniline using silyl hydrides as reductants has been examined. The chemoselective reduction of imines takes place under mild conditions to afford the corresponding amines in nearly quantitative yield. Mechanistic studies indicate that dissociation of the ancillary ligands generate the active catalyst in all the complexes studied, which is the same species generated by [Ru( p‐ cymene)(Cl) 2 ] 2 under the reaction conditions. This results in the formation of a single catalytic species irrespective of the starting half‐sandwich complex. Detailed mechanistic studies involving trapping of intermediates, in situ studies using mass spectrometry and NMR spectroscopy were carried out using the active catalyst generated by [Ru( p‐ cymene)(Cl) 2 ] 2 . The mechanism of the reaction is dependent on the number of the hydrogen atoms in the reducing silane. The reaction proceeds via Gade‐Hoffman pathway or Zheng‐Chan pathway when a dihydro or trihydrosilane is the reductant. However, the use of a monohydrosilane, leads to longer reaction times presumably due to a change in the reaction pathway.