140631-53-4Relevant articles and documents
The kinetics and mechanism of the organo-iridium catalysed racemisation of amines
Stirling, Matthew J.,Mwansa, Joseph M.,Sweeney, Gemma,Blacker, A. John,Page, Michael I.
, p. 7092 - 7098 (2016)
The dimeric iodo-iridium complex [IrCp?I2]2 (Cp? = pentamethylcyclopentadiene) is an efficient catalyst for the racemisation of secondary and tertiary amines at ambient and higher temperatures with a low catalyst loading. The racemisation occurs with pseudo-first-order kinetics and the corresponding four rate constants were obtained by monitoring the time dependence of the concentrations of the (R) and (S) enantiomers starting with either pure (R) or (S) and show a first-order dependence on catalyst concentration. Low temperature 1H NMR data is consistent with the formation of a 1 : 1 complex with the amine coordinated to the iridium and with both iodide anions still bound to the metal-ion, but at the higher temperatures used for kinetic studies binding is weak and so no saturation zero-order kinetics are observed. A cross-over experiment with isotopically labelled amines demonstrates the intermediate formation of an imine which can dissociate from the iridium complex. Replacing the iodides in the catalyst by other ligands or having an amide substituent in Cp? results in a much less effective catalysts for the racemisation of amines. The rate constants for a deuterated amine yield a significant primary kinetic isotope effect kH/kD = 3.24 indicating that hydride transfer is involved in the rate-limiting step.
Protic additives or impurities promote imine reduction with pinacolborane
Huchenski, Blake S. N.,Speed, Alexander W. H.
supporting information, p. 1999 - 2004 (2019/02/20)
We report here that addition of stoichiometric amounts of alcohols or water to mixtures of imines and pinacolborane promote reduction reactions. The reactions of several imines were examined, revealing that alkyl imines were reduced, while aniline derived imines were not effectively reduced. The use of binol as an additive resulted in modest enantioinduction, however other chiral additives that were screened gave negligible enantioinduction. While the reactions described herein are not competitive in conversion with established imine reduction technologies, this work reveals that the presence of protic impurities must be considered as a promoter of side reactions in catalyzed imine hydroborations. Amines also promote imine reduction in certain cases, raising the possibility of a slow autocatalytic reaction. The ability of water or other protic impurities to promote the reduction of imines with pinacolborane represents an important identification of a potential source of background reaction in catalyzed reductions of imines.
Continuous flow hydrogenation of a pharmaceutical intermediate, [4-(3,4-dichlorophenyl)-3,4-dihydro-2H-naphthalenyidene]-methylamine, in supercritical carbon dioxide
Clark, Peter,Poliakoff, Martyn,Wells, Andy
, p. 2655 - 2659 (2008/09/19)
The hydrogenation of complex pharmaceutical intermediate, rac-sertraline imine has been optimized as a continuous flow process utilizing a palladium/calcium carbonate (Pd/CaCO3) catalyst and hydrogen in supercritical carbon dioxide (scCO2
