Achiral benzophenone ligand-rhodium complex with chiral diamine activator for high enantiocontrol in asymmetric transfer hydrogenation

The chirality of an achiral benzophenone-based rhodium complex can be controlled by chiral diamines to afford significantly high enantioselectivity in the catalytic asymmetric transfer hydrogenation of ketones (up to 99% ee, 99% yield).     

Iridium and rhodium complexes with the planar chiral thioether ligands in asymmetric hydrogenation of ketones and imines

Rhodium complexes with the planar chiral phosphinoferrocenyl thioether ligands [Rh(P,SR)(diene)X] (R = Me, Bu^t, Ph, Bn, diene is cyclooctadiene (COD) or norbornadiene (NBD), X = Cl, BF₄) catalyze hydrogenation of ketones, imines, and heteroaromatic compounds; in the case of acetophenone, the enantioselectivity reached 60% ee. Similar iridium complexes demonstrate a good activity in the hydrogenation of imines, the maximal enantioselectivity in the case of N-phenyl-N-(1-phenylethylidene)amine was about 40% ee.     

Catalytic asymmetric hydrogenation of indoles using a rhodium complex with a chiral bisphosphine ligand PhTRAP

Highly enantioselective hydrogenation of N-protected indoles was successfully developed by use of the rhodium catalyst generated in situ from [Rh(nbd)₂]SbF₆ and the chiral bisphosphine PhTRAP, which can form a trans-chelate complex with a transition metal atom. The PhTRAP–rhodium catalyst required a base (e.g., Cs₂CO₃) for the achievement of high enantioselectivity. Various 2-substituted N-acetylindoles were converted into the corresponding chiral indolines with up to 95% ee. The hydrogenations of 3-substituted N-tosylindoles yielded indolines possessing a stereogenic center at the 3-position with high enantiomeric excesses (up to 98% ee).     

Catalytic asymmetric carbalkoxyallylation of imines with the chiral bis-pi-allylpalladium complex

Carbethoxyallylstannane was employed along with the bis-pi-allylpalladium complex to achieve a useful conversion of prochiral imines to chiral 2-(2-aryl-2-aminoethyl)acrylates which are important building blocks for further asymmetric synthesis of a wide range of compounds.     

New chiral diphosphoramidite rhodium(I) complexes for asymmetric hydrogenation

Chiral 1,5‐cyclooctadiene rhodium(I) cationic complexes with C₂‐symmetric chelate diphosphoramidite ligands containing (R,R)‐1,2‐diaminocyclohexane as the backbone and two atropoisomeric biaryl units were easily synthesized and fully characterized by multinuclear one‐ and two‐dimensional NMR spectroscopy and elemental analysis. These complexes were used as catalysts in the asymmetric hydrogenation of dimethyl itaconate, methyl 2‐acetamidoacrylate and (Z)‐methyl‐2‐acetamido‐3‐phenylacrylate. The rhodium complexes derived from diphosphoramidite ligands that contain two (R) or (S) BINOL (2,2′‐dihydroxy‐1,1′‐binaphthyl) units proved to be efficient catalysts, giving complete conversion and very good enantioselectivity (up to 88% ee). An uncommon positive H₂ pressure effect on the enantioselectivity was observed in the hydrogenation of dimethyl itaconate catalyzed by Rh‐complex with diphosphoramidite ligand that contains two (S)‐binaphthol moieties. Copyright © 2014 John Wiley & Sons, Ltd.     

A new chiral sulfinyl-NH-pyridine ligand for Ir-catalyzed asymmetric transfer hydrogenation reaction

A new flexible C₁-symmetric tridentate ligand (S)-N-(2-(tert-butylsulfinyl)benzyl)-1-(pyridin-2-yl)methanamine sulfoxide (L1) was successfully prepared and utilized as a chiral ligand for Ir(I)-catalyzed ATH (asymmetric transfer hydrogenation) reactions. Without any cooperation of other chiral center, encouraging ee and conversion values have been achieved, which provide us a better understanding on these types of ligands and a new strategy to develop new high-efficiency chiral catalysts for asymmetric reaction.     

Structure effect of TsDPEN derivatives on enantioselectivity of asymmetric transfer hydrogenation

TsDPEN derivative (3,3′,5,5′-TMTsDPEN) was synthesized and applied in asymmetric transfer hydrogenation of ketones. The influence of chiral ligands’ NCCN dihedral angles to the enantioselectivities of the reaction was discussed.     

A stereochemically well-defined rhodium(III) catalyst for asymmetric transfer hydrogenation of ketones

[reaction: see text] A rhodium(III) catalyst for asymmetric transfer hydrogenation of ketones has been designed. The incorporation of a tethering group between the diamino group and the cyclopentadienyl unit provides extra stereochemical rigidity. The catalyst is capable of enantioselective reduction of a range of ketones in excellent ee using formic acid/triethylamine as both the solvent and the reducing agent.     

Catalytic asymmetric Michael reactions using a chiral rhodium complex

Catalytic asymmetric Michael reaction of β-keto esters and methyl vinyl ketone was achieved using a chiral diamine-based Rh complex to give the Michael adducts in up to 75% e.e.     

A novel asymmetric reduction of imines with chiral sodium triacyloxyborohydrides

There has been described a novel and convenient synthesis of optically active alkaloids by the asymmetric reduction of cyclic imines using the chiral sodium triacyloxyborohydrides, easily prepared from the reaction of NaBH₄ and N-acyl L-prolines.     

喹啉及其衍生物的多相不对称氢转移反应

喹啉及其衍生物的多相不对称氢转移是制备杂环手性化合物的理想策略.多相手性催化体系具有催化剂可循环利用及产物分离提纯容易等优势.然而,喹啉及其衍生物的多相手性高效催化体系鲜有报道.这主要是由于多相手性氢转移为水-油-固三相反应,在反应的过程中,传质问题极大影响固体催化剂的催化性能.因此,发展具有相转移功能的手性催化材料,...     

Chelating bis-carbene rhodium(III) complexes in transfer hydrogenation of ketones and imines

Chelating rhodium(III) carbene complexes are accessible via a simple synthesis and are catalytically active for hydrogen transfer from alcohols to ketones and imines.     

Chiral counteranion-aided asymmetric hydrogenation of acyclic imines

When combined with a chiral phosphate counteranion, a chiral diamine-ligated Ir(III) catalyst displayed excellent enantioselectivities in the asymmetric hydrogenation of a wide range of acyclic imines, affording chiral amines in up to 99% ee.     

Asymmetric hydrogenation with antibody-achiral rhodium complex

Monoclonal antibodies have been elicited against an achiral rhodium complex and this complex was used in the presence of a resultant antibody, 1G8, for the catalytic hydrogenation of 2-acetamidoacrylic acid to produce N-acetyl-L-alanine in high (>98%) enantiomeric excess.     

Catalytic asymmetric synthesis of N-acetylphenylalanine in presence of chiral rhodium complex

Conclusions The hydrogenation, of-acetylaminocinnamic acid under homogeneous conditions in the presence of the system (Py)₃RhCl₃·NaBH₄·(S)-(-)-N--phenylethylformamide gives (R)-(-)-acetylphenylalanine in a yield of 66.2% and an optical yield of 73.8%.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, p. 2374, October, 1975.     

Design of novel polymer-supported chiral catalyst for asymmetric transfer hydrogenation in water

New polymer-supported chiral sulfonamides containing sulfonated pendant group have been synthesized. Chiral catalyst prepared from the new polymer-support is more effective for asymmetric transfer hydrogenation of aromatic ketones in water compared to that prepared from conventional polystyrene-support. Polymer-supported catalysts containing quaternary ammonium salt as a pendant increased not only the reactivity but also the enantioselectivity in asymmetric transfer hydrogenation in water. Moreover, this type of polymer can be reused without loss of the catalytic activity.     

Iridium complex bearing a chiral hydroxy-amide functionalized N-heterocyclic carbene: a catalyst precursor for asymmetric transfer hydrogenation

A new monodentate iridium(III) complex bearing a readily accessible and tunable chiral hydroxy-amide functionalized N-heterocyclic carbene ligand, Cp^∗Ir(NHC)Cl₂, has been synthesized and characterized by crystallographic methods. The monodentate Cp^∗Ir(NHC)Cl₂ complex was found to act as a catalyst precursor for the stereoselective transfer hydrogenation of acetophenone in the presence of KOH even at room temperature. Moderate enantioselectivity was observed in the initial screening of the chiral ligands.     

Heterogenised iridium complexes for the asymmetric hydrogenation of imines

A method for immobilising preformed chiral homogeneous catalysts to a clay support material has been developed. The observed asymmetric induction in the hydrogenation of imines with the supported species was greater than that with the corresponding homogeneous catalysts and, on re-use, the supported species increased their enantioselectivity.     

Phosphines versus phosphinites as ligands in the rhodium catalyzed asymmetric hydrogenation of imines: a systematic study

The asymmetric hydrogenation of N-(1-phenylethylidene)benzylamine with a range of rhodium(I)-diphosphine and diphosphinite catalysts is studied. The reaction is strongly sensitive to the size of the metal chelate. Complexes based on five- and six-membered chelates or electron-rich alkylphosphines gave poor or moderate conversions. The reactivity of diphosphine catalysts could be increased by the addition of p-toluenesulfonic acid. Unexpectedly, Rh-complexes based on chiral diphosphinites and a diphosphite also rapidly converted the substrate to the desired amine. Highest efficiency was observed with a rhodium(I) complex with (R,R)-1,2-cyclohexanol-bisdiphenylphosphinite [(R,R)-bdpch] as chiral ligand. Without any additive complete hydrogenation of the imine was achieved within 5 h. The product was produced in an enantioselectivity of 71%.