Trans-chelating Chiral Diphosphine Research Articles

ChemInform Abstract: Catalytic Asymmetric Hydrogenation of 1-Aza-2-cycloalkene-2-carboxylates Catalyzed by a trans-Chelating Chiral Diphosphine PhTRAP-Rhodium Complex.

Abstract A rhodium complex coordinated with a trans -chelating chiral diphosphine (S,S)-(R,R) -PhTRAP was an effective catalyst for asymmetric hydrogenation of N -acyl-1-aza-2-cycloalkene-2-carboxylates, which gave the corresponding protected cyclic α-amino acids with 73–97% ee.

ChemInform Abstract: Design and Synthesis of Optically Active Trans-Chelating Diphosphine Ligands. Application for Catalytic Asymmetric Synthesis

New chiral diphosphines 2,2“-bis[1-(disubstituted phosphino)ethyl]-1,1”-biferrocene, having both central and planar elements of chirality, was designed for a trans-chelating chiral diphosphine ligand (TRAP) for transition metals and synthesized form optically active N,N-dimethyl-1-ferrocenyl ethylamine. Some transition-metal complexes with the TRAP ligands were prepared and utilized as a chiral catalyst for asymmetric synthetic reactions.

Rhodium-Catalyzed Enantioselective Michael Addition of (1-Cyanoethyl)phosphonate: Synthesis of Optically Active Phosphonic Acid Derivatives with Phosphorus-Substituted Quaternary Asymmetric Carbon Center

Abstract Asymmetric Michael addition of diethyl (1-cyanoethyl)phosphonate with vinyl ketones or acrylaldehyde in the presence of 0.01 molar amount of a rhodium catalyst prepared in situ from Rh(acac)(CO)2 and a trans-chelating chiral diphosphine ligand (R,R)-(S,S)-2,2′′-bis[1-(diphenylphosphino)ethyl]-1,1′′-biferrocene (PhTRAP) in benzene at 3 °C gave optically active phosphonates having a phosphorus-substituted quaternary asymmetric carbon center with high enantiomeric excesses (92—93% ee) in high yields. The Michael addition product from acrylaldehyde was converted into an optically active (1-aminoalkyl)phosphonic acid derivative.

ChemInform Abstract: Asymmetric Aldol Reaction of 2-Cyanopropionates Catalyzed by a trans-Chelating Chiral Diphosphine-Rhodium(I) Complex: Highly Enantioselective Construction of Quaternary Chiral Carbon Centers at α-Positions of Nitriles.

Abstract The aldol reaction of 2-cyanopropionates with aldehydes proceeded under neutral conditions in the presence of a catalytic amount of the rhodium complex generated in situ from Rh(acac)(CO) 2 and triphenylphosphine, to give the corresponding β-hydroxy-α-cyanocarboxylates bearing a quaternary chiral carbon center at the α-position of the cyano group. A high degree of asymmetric induction for the aldol reaction was achieved by use of trans-chelating chiral diphosphine ligands, ( R , R )-2,2″-bis[( S )-1-(diarylphosphino)ethyl]-1,1″-biferrocenes (TRAPs). The asymmetric aldol reactions gave optically active β-hydroxy-α-cyanocarboxylates with up to 94% ee.

Asymmetric aldol reaction of 2-cyanopropionates catalyzed by a trans-chelating chiral diphosphine–rhodium(I) complex: highly enantioselective construction of quaternary chiral carbon centers at α-positions of nitriles

The aldol reaction of 2-cyanopropionates with aldehydes proceeded under neutral conditions in the presence of a catalytic amount of the rhodium complex generated in situ from Rh(acac)(CO) 2 and triphenylphosphine, to give the corresponding β-hydroxy-α-cyanocarboxylates bearing a quaternary chiral carbon center at the α-position of the cyano group. A high degree of asymmetric induction for the aldol reaction was achieved by use of trans-chelating chiral diphosphine ligands, ( R, R)-2,2″-bis[( S)-1-(diarylphosphino)ethyl]-1,1″-biferrocenes (TRAPs). The asymmetric aldol reactions gave optically active β-hydroxy-α-cyanocarboxylates with up to 94% ee.

Catalytic asymmetric hydrogenation of 1-aza-2-cycloalkene-2-carboxylates catalyzed by a trans-chelating chiral diphosphine PhTRAP-rhodium complex

A rhodium complex coordinated with a trans-chelating chiral diphosphine (S,S)-(R,R)-PhTRAP was an effective catalyst for asymmetric hydrogenation of N-acyl-1-aza-2-cycloalkene-2-carboxylates, which gave the corresponding protected cyclic α-amino acids with 73–97% ee.

Synthesis of a trans-chelating chiral diphosphine ligand with only planar chirality and its application to asymmetric hydrosilylation of ketones

Optically active diphosphine (S,S)-2,2″-bis[(diethylphosphino)methyl]-1,1″-biferrocene (abbreviated to (S,S)-EtTRAP-H) was synthesized from ferrocenyloxazoline derived from l-valinol in 47% overall yield. The new chiral ligand, (S,S)-EtTRAP-H, which coordinates to a rhodium atom in a trans-chelating manner, was effective for asymmetric hydrosilylation of ketones to give optically active secondary alcohols with up to 94% ee.

Design and Synthesis of Optically Active Trans-Chelating Diphosphine Ligands. Application for Catalytic Asymmetric Synthesis

New chiral diphosphines 2,2“-bis[1-(disubstituted phosphino)ethyl]-1,1”-biferrocene, having both central and planar elements of chirality, was designed for a trans-chelating chiral diphosphine ligand (TRAP) for transition metals and synthesized form optically active N,N-dimethyl-1-ferrocenyl ethylamine. Some transition-metal complexes with the TRAP ligands were prepared and utilized as a chiral catalyst for asymmetric synthetic reactions.

Asymmetric hydrogenation of ( E)-α,β-bis( N-acylamino)acrylates catalyzed by a rhodium complex with trans-chelating chiral diphosphine ligand

The asymmetric hydrogenation of ( E)-α,β-bis( N-acylamino)acrylates was promoted by a rhodium complex bearing a trans-chelating chiral diphosphine ligand ( R, R)-( S, S)-PrTRAP, providing the corresponding optically active (2 S,3 R)-2,3-bis( N-acylamino)carboxylates with 79–82% ee. The 2,3-bis( N-acylamino)carboxylates isolated were readily hydrolyzed under acid to afford (2 S,3 R)-2,3-diaminocarboxylic acids in 95% yield without epimerization.

Asymmetric aldol reaction of 2-cyanopropionates catalysed by trans-chelating chiral diphosphine ligand TRAP–rhodium(I) complex

trans-Chelating chiral diphosphine TRAP ligands bearing P-aromatic groups are effective for RhI-catalysed asymmetric aldol reaction of 2-cyanopropionates with an aldehyde to give the corresponding aldol adduct with up to 93% ee.

Catalytic asymmetric hydrogenation of dimethyl itaconate with trans-chelating chiral diphosphine ligands TRAP-rhodium complexes

Abstract Asymmetric hydrogenation of dimethyl itaconate catalyzed by the trans-chelating chiral diphosphine ( R , R )-( S , S )-EtTRAP-rhodium complex gave ( S )-dimethyl 2-methylsuccinate with 96% ee. Dimethyl 2-isopropylidenesuccinate, a tetrasubstituted olefin substrate, was also hydrogenated with ( R , R )-( S , S )-BuTRAP-rhodium complex in high enantioselectivity (78% ee), but with opposite enantioselection.

Asymmetric Michael reaction of an α-cyano Weinreb amide catalyzed by a rhodium complex with trans-chelating chiral diphosphine PhTRAP

Asymmetric Michael reaction of N-methoxy- N-methyl-2-cyanopropionamide with vinyl ketones or acrolein in the presence of 0.1–1 mol% of a rhodium catalyst prepared in situ from Rh(acac)(CO) 2 and a trans-chelating chiral diphosphine ligand ( S, S)-( R, R)-PhTRAP gave optically active Michael adducts with high enantiomeric excesses (89–94%) in high yields. The adducts with methyl vinyl ketone was transformed into an α-cyano aldehyde and ketones with an quarternary asymmetric carbon center through the reaction with LiAlH 4 or Grignard reagents.

Asymmetric Hydrosilylation of Symmetrical Diketones Catalyzed by a Rhodium Complex with Trans-Chelating Chiral Diphosphine EtTRAP

Asymmetric hydrosilylation of symmetrical diketones with diphenylsilane in the presence of catalytic amount ([substrate]/[catalyst] = 100) of rhodium complex coordinated with trans-chelating chiral phosphine ligand EtTRAP gave corresponding optically active symmetrical diols with high enantiomeric excesses.

Asymmetric hydrosilylation of symmetrical diketones catalyzed by a rhodium complex with trans-chelating chiral diphosphine EtTRAP

Asymmetric hydrosilylation of symmetrical diketones with diphenylsilane in the presence of catalytic amount ([substrate]/[catalyst] = 100) of rhodium complex coordinated with trans-chelating chiral phosphine ligand EtTRAP gave corresponding optically active symmetrical diols with high enantiomeric excesses. Optically active C 2 -symmetrical diols were prepared by asymmetric hydrosilylation of various diketones catalyzed by EtTRAP-rhodium complex.

Asymmetric Hydrosilylation of Keto Esters Catalyzed by a Rhodium Complex with Trans-Chelating Chiral Diphosphine EtTRAP

Asymmetric Hydrosilylation of Keto Esters Catalyzed by a Rhodium Complex with Trans-Chelating Chiral Diphosphine EtTRAP

Asymmetric Michael reaction of α-cyano carboxylates catalyzed by a rhodium complex with trans-chelating chiral diphosphine PhTRAP

Asymmetric Michael reaction of 2-cyanopropionates with vinyl ketones or acrolein in the presence of 0.1–1 mol% of a rhodium catalyst prepared in situ from RhH(CO)(PPh 3) 3 and a trans-chelating chiral diphosphine ligand ( S,S)-( R,R)-PhTRAP in benzene at 3–5°C gave optically active Michael adducts with high enantiomeric excesses (83–93% ee) in high yields. The reaction of 2-cyanopropionate with methacrolein and crotonaldehyde proceeded somewhat slowly, giving diastereomer mixtures in moderate enantioselectivities but in low diastereoselectivities. The reaction of 2-cyanobutyrate and 2-cyano-3-methylbutyrate with acrolein gave corresponding Michael adducts with much lower enantiomeric excesses than that of 2-cyanopropionates. The Michael addition product from acrolein was converted into an optically active α-methyl-α-amino acid.

Catalytic asymmetric synthesis with trans-chelating chiral diphosphine ligand TRAP: rhodium-catalyzed asymmetric Michael addition of .alpha.-cyano carboxylates

Catalytic asymmetric synthesis with trans-chelating chiral diphosphine ligand TRAP: rhodium-catalyzed asymmetric Michael addition of .alpha.-cyano carboxylates

A trans-chelating chiral diphosphine ligand: Synthesis of 2,2″-bis[1-(diphenylphosphino)ethyl]-1,1″-biferrocene and its complexes with platinum(II) and palladium(II)

A new chiral diphosphine ligand, ( R,R)-( S,S)-2,2″-bis[1-(diphenylphosphino)ethyl]-1,1″-biferrocene, which possesses both central and planar elements of chirality, was synthesized. The NMR studies and molecular weight determination indicated that the ligand chelates to platinum(II) and palladium(II) in trans-manner.