Remarkable co-catalyst effects on the enantioselective hydrogenation of unfunctionalised enamines: both enantiomers of product from the same enantiomer of catalyst

Tin, Sergey; Fanjul, Tamara; Clarke, Matthew L.

doi:10.1039/c5cy02051d

Cited by 10 publications

(10 citation statements)

References 33 publications

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“…In the literature, it is intensively discussed whether the enamine or the iminium ion intermediate is finally reduced to an amine. [5,6] Since this is a simple hydrogenation reaction of a double bond, mainly heterogeneous catalysts are applied for this task. [3] However, also a range of homogeneous hydrogenation catalysts does exist.…”

Section: Introductionmentioning

confidence: 99%

Rhodium‐Catalysed Reductive Amination for the Synthesis of Tertiary Amines

et al. 2020

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A procedure for the synthesis of tertiary amines via reductive amination of aldehydes with molecular hydrogen as a reducing agent using homogeneous rhodium catalysis is presented. Using an amine to aldehyde ratio of 4/1 enabled the synthesis of tertiary amines from nine different aldehydes and nine different secondary amines with selectivities up to 99% and turnover frequencies (TOF) up to 7200 h À 1. The reaction showed a high tolerance against alcohol and ester functions allowing the formation of multifunctional molecules. In addition, secondary amines can also be produced by this synthesis. For all compounds, activities were determined by hydrogen gas-uptake. In order to increase the sustainability and efficiency of the procedure, a dosing strategy has been successfully developed. Using the determined reaction indicators enabled the stoichiometric use of aldehydes and amines without significant loss of selectivity.

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Section: Introductionmentioning

confidence: 99%

Rhodium‐Catalysed Reductive Amination for the Synthesis of Tertiary Amines

et al. 2020

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“…Along this catalytic cycle, the nature of the ligands, and thus the coordination sphere, is crucial for providing a good hydrogenation activity and eventually a high enantioselectivity. 51,52 Actually two catalytic cycles can be considered. It is admitted that the neutral [Rh] active species reacts with dihydrogen by an oxidative addition reaction to give the [Rh(H) 2 ] dihydride.…”

Section: Successive Hydroformylation and Hydrogenation Catalytic Cyclesmentioning

confidence: 99%

“…Reductive elimination of the alkyl group and the hydride ligand leads to the final amine and restores the [Rh] active species. Since recent studies on the hydrogenation of enamines have demonstrated that a cationic intermediate involving an iminium ion is involved, 51 a cationic [Rh] + active species can be considered with a Rh-η 2 -dihydrogen complex that transfers a proton to the nitrogen atom of the enamine followed by addition of the rhodium-hydride.…”

Section: Successive Hydroformylation and Hydrogenation Catalytic Cyclesmentioning

confidence: 99%

“…Then the produced aldehydes immediately react with the primary or secondary amine present in the medium to afford the corresponding enamine and iminium intermediates, the linear aldehyde being largely more reactive than the branched one in this condensation reaction . Hydrogenation of these two intermediates leading to the expected amines has been reviewed, − and the mechanism analyzed in the literature allows the second catalytic cycle displayed in Scheme to be proposed. It is devoted to the RCHCHNR 1 R 2 enamine hydrogenation, showing the main catalytic steps involving the neutral or cationic rhodium active species, represented as [Rh] and [Rh] + for simplification.…”

Section: Mechanism and Selectivitymentioning

confidence: 99%

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Tandem Hydroaminomethylation Reaction to Synthesize Amines from Alkenes

2018

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In the context of atom economy and low environmental impact, synthesis of amines by an efficient catalytic process is of great importance to produce these building blocks for fine chemical industry. The one-pot hydroaminomethylation of alkenes is a tandem reaction which involves three successive steps under CO/H pressure to perform the catalyzed hydroformylation of the alkene into the corresponding aldehyde followed by its condensation with a N-H function and the catalyzed hydrogenation of the imine/enamine intermediate into the corresponding saturated amine. Rhodium and more recently ruthenium complexes have been designed to combine high conversions of the reactants and chemoselectivity in the expected amines with high regioselectivity in either the linear or the branched amine. The coordination sphere of the metal according to the presence of ligands, temperature, CO/H partial pressures, and nature of the solvent is essential for complying with these selectivity requirements. The rate of the hydroformylation step needs to be fast with regard to the hydrogenation step. The role of amines in the coordination sphere and water, presumably in the second sphere, on the mechanism requires some more studies. Similarly, the enantioselective synthesis of amine is not yet achieved directly and interrupted processes or use of asymmetric organo-catalyzed reductive amination are efficient synthetic ways for producing chiral amines. The separation of the catalyst from the organic products by biphasic or (semi-) heterogeneized systems and its recycling have been demonstrated in many cases. The present review provides a report of the state of the art in this autotandem hydroaminomethylation catalysis and should open prospects in the design of less expensive and abundant metal complexes for reaching at low cost similar and even superior performances.

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“…The overall thermodynamics of the RA of undecanal 1 with diethylamine 2 are only marginally dependent on the polarity of the solvent by ∼4 kJ/mol with polar media such as DMF ( N,N -dimethylformamide) being preferred. The COSMO and COSMO-RS solvent effects on the free energy of the reaction give approximately the same ordering of solvent candidates as UNIFAC(Do) (see Supporting Information).…”

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confidence: 99%

Solvent Selection in Homogeneous Catalysis—Optimization of Kinetics and Reaction Performance

et al. 2020

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Solvents have an enormous impact on yield and turnover of chemical reactions in complex media. There is, however, a lack of consistent model-based tools to a priori identify the appropriate solvent for homogeneously catalyzed reactions. Here, a thermodynamically consistent approach for a reductive amination reaction is presented. It combines solvent screening using a thermodynamic-activity model and quantum chemical calculations. The optimization of activity coefficient-based predicted kinetics gives a suitable list of candidate solvents. The results were confirmed by batch experiments in selected solvents. This approach allows reducing time and lab resources for solvent selection to a minimum.

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Remarkable co-catalyst effects on the enantioselective hydrogenation of unfunctionalised enamines: both enantiomers of product from the same enantiomer of catalyst

Abstract: A switch in enantioselectivity is observed when iodine is used as a co-catalyst in the hydrogenation of unfunctionalised enamines. Mechanistic studies implicate a stepwise protonation-hydride reduction pathway.

Cited by 10 publications

References 33 publications

Rhodium‐Catalysed Reductive Amination for the Synthesis of Tertiary Amines

Rhodium‐Catalysed Reductive Amination for the Synthesis of Tertiary Amines

Tandem Hydroaminomethylation Reaction to Synthesize Amines from Alkenes

Solvent Selection in Homogeneous Catalysis—Optimization of Kinetics and Reaction Performance

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