Chiral Phosphine Oxides Research Articles

ChemInform Abstract: Chiral Phosphine Oxide—Sc(OTf)3 Complex Catalyzed Enantioselective Bromoaminocyclization of 2‐Benzofuranylmethyl N‐Tosylcarbamates. Approach to a Novel Class of Optically Active Spiro Compounds.

AbstractThe scalable title reaction provides bromo‐substituted spiro benzofuran oxazolidinones in moderate to often high yields with very high enantiomeric excesses.

ChemInform Abstract: Minimizing Aryloxy Elimination in RhI‐Catalyzed Asymmetric Hydrogenation of β‐Aryloxyacrylic Acids Using a Mixed‐Ligand Strategy.

AbstractAn efficient asymmetric hydrogenation of β‐aryloxyacrylic acids is realized using a Rh(I)‐complex based on the heterocombination of a readily available chiral monodentate secondary phosphine oxide (SPO) and an achiral monodentate phosphine ligand as the catalyst.

Stereoselective Synthesis of Highly Functionalized 2,3-Dihydro-4-pyranones Using Phosphine Oxide as Catalyst.

2,3-Dihydro-4-pyranones were synthesized stereoselectively using a chiral phosphine oxide as the catalyst. The phosphine oxide sequentially activated silicon tetrachloride and promoted the double aldol reaction of 4-methoxy-3-buten-2-one with aldehydes. Subsequent stereoselective cyclization afforded the corresponding highly functionalized 2,3-dihydro-4-pyranones bearing three contiguous chiral centers in good yields and with high diastereo- and enantioselectivities.

The synthesis and efficient one-pot catalytic "self-breeding" of asymmetrical NC(sp(3))E-hybridised pincer complexes.

Cyclopalladation of the pyridyl-substituted chiral phosphine sulfide (N-P=S) and oxide (N-P=O) compounds afforded the asymmetric N-C(sp(3))*-S and N-C(sp(3))*-O pincer complexes. When applied as catalysts in asymmetric hydrophosphination, the newly developed aliphatic pincer catalyst could be recycled over three runs and obtained in large quantities via a one-pot "self-breeding" catalytic protocol.

Enantioselective hydrogenation of ketones by iridium nanoparticles ligated with chiral secondary phosphine oxides

Chiral iridium nanoparticles (IrNPs) were synthesized by H2reduction of (1,5-cyclooctadiene)(methoxy)iridium(i) dimer ([Ir(OMe)(COD)]2) in the presence of an asymmetric secondary phosphine oxide.

ChemInform Abstract: Chiral Phosphine Oxide Aziridinyl Phosphonate as a Lewis Base Catalyst for Enantioselective Allylsilane Addition to Aldehydes.

Abstract A series of chiral Lewis bases, phosphine oxide ferrocenyl aziridinyl methanol 1–4, phosphinyl aziridinyl phosphonates 5 and 6, and phosphine oxide aziridinyl phosphonates 7 and 8 were screened for allylsilane additions to aldehydes. Among the Lewis bases, 8 was found to catalyze the reaction by forming the product in up to 94% yield and with 77% ee.

Chiral Phosphine Oxide-Sc(OTf)3 Complex Catalyzed Enantioselective Bromoaminocyclization of 2-Benzofuranylmethyl N-Tosylcarbamates. Approach to a Novel Class of Optically Active Spiro Compounds.

An efficient enantioselective bromoaminocyclization of 2-benzofuranylmethyl N-tosylcarbamates catalyzed by a chiral phosphine oxide-Sc(OTf)(3) complex is described. A wide variety of optically active spiro benzofuran oxazolidinones can be obtained with high enantioselectivities.

Minimizing Aryloxy Elimination in Rh(I) -Catalyzed Asymmetric Hydrogenation of β-Aryloxyacrylic Acids using a Mixed-Ligand Strategy.

The first example of efficient asymmetric hydrogenation of challenging β-aryloxyacrylic acids was realized using a Rh(I) -complex based on the heterocombination of a readily available chiral monodentate secondary phosphine oxide (SPO) and an achiral monodentate phosphine ligand as the catalyst. Excellent enantioselectivities (92->99 % ee) were achieved for a wide variety of chiral β-aryloxypropionic acids with minor aryloxy elimination in most cases. The resultant products were readily transformed into biologically active compounds through simple synthetic manipulations.

Chiral phosphine oxide aziridinyl phosphonate as a Lewis base catalyst for enantioselective allylsilane addition to aldehydes

A series of chiral Lewis bases, phosphine oxide ferrocenyl aziridinyl methanol 1–4, phosphinyl aziridinyl phosphonates 5 and 6, and phosphine oxide aziridinyl phosphonates 7 and 8 were screened for allylsilane additions to aldehydes. Among the Lewis bases, 8 was found to catalyze the reaction by forming the product in up to 94% yield and with 77% ee.

Synthesis of novel chiral bithiophenebased phosphine oxides as Lewis bases in organocatalytic stereoselective reactions

Abstract Novel enantiomerically pure tetramethylbithiophene diphosphine oxides (tetraMe-BITIOPO) featuring differently substituted aromatic rings at the phosphorous atoms were synthesized, fully characterized and isolated in enantiomerically pure form. The new Lewis bases were tested as organocatalysts in two different reactions involving trichlorosilyl compounds. The introduction of electron donating substituents on the aromatic rings connected to the phosphine oxide groups positively affected the chemical and stereochemical catalytic efficiency of these ligands. The new catalysts were able to promote the allylation of aldehydes with allyltrichlorosilane in up to 76% yield and up to 86% enantiomeric excess (ee), and the direct aldol reaction to afford β-hydroxy ketones in high diastereoselectivity (up to 88:12 anti:syn ratio) and up to 72% ee.

Phosphine Oxide Catalyzed, Tetrachlorosilane-Mediated Enantioselective Direct Aldol Reactions of Thioesters

The stereoselective direct aldol reaction of S-phenyl thioesters and aromatic aldehydes promoted by tetrachlorosilane was realized for the first time; the proposed mechanism involves the formation of a chiral cationic hypervalent silicon species and requires the presence of catalytic amounts of a Lewis base, like a chiral phosphine oxide. The reaction affords syn β-hydroxy thioesters as major isomers in good yields, high diastereoselectivity (up to 99:1), and up to 92% enantiomeric excess. The absolute configuration of the major isomer was established by converting the product into the corresponding β-hydroxy ester. The scope of the reaction was also investigated by employing differently substituted thioesters in combination with different aromatic aldehydes.

ChemInform Abstract: PCN Pincer Palladium(II) Complex Catalyzed Enantioselective Hydrophosphination of Enones: Synthesis of Pyridine‐Functionalized Chiral Phosphine Oxides as NCsp3O Pincer Preligands.

A series of chiral PCN pincer Pd(II) complexes VI–XIII with aryl-based aminophosphine–imidazoline or phosphinite–imidazoline ligands were synthesized and characterized. They were examined as enantioselective catalysts for the hydrophosphination of enones. Among them, complex IX, which features a Ph2PO donor as well as an imidazoline donor with (4S)-phenyl and N-Tol-p groups, was found to be the optimal catalyst. Thus, in the presence of 2–5 mol % of complex IX a wide variety of enones reacted smoothly with diarylphosphines to give the corresponding chiral phosphine derivatives in high yields with enantioselectivities of up to 98% ee. In particular, heteroaryl species such as 2-thienyl-, 2-furyl-, and 2-pyridinyl-containing enones that have a strong coordination ability to the Pd center were also appropriate substrates for the current catalytic system. For example, hydrophosphination of 2-alkenoylpyridines with diphenylphosphine followed by oxidation with H2O2 afforded the corresponding pyridine-functional...

ChemInform Abstract: Catalyst‐Free Three‐Component Reaction to Synthesize Chiral α‐Amino Phosphine Oxides.

A three-component reaction for high diastereoselective synthesis of chiral α-amino phosphine oxides has been developed and displayed environmentally friendly and atom efficient characteristics. The reaction proceeds smoothly without catalysts or additives.

ChemInform Abstract: Phosphine Oxide‐Catalyzed Enantioselective Intramolecular Aldol Reaction via Regioselective Enolization of Unsymmetrical Diketones with Tetrachlorosilane.

The phosphine oxide-catalyzed asymmetric intramolecular aldol reactions of diketones were investigated. The combination of tetrachlorosilane and a chiral phosphine oxide catalyst promoted the acetyl-selective enolization of diketones, and the subsequent intramolecular aldol reaction occurred in an enantioselective manner. The introduction of two trimethylsilyl groups at the 4- and 4′-positions in BINAP dioxide catalyst improved the enantioselectivity. This reaction provides an effective synthetic method to access β-tertiary-hydroxy cyclohexanones in high yields and with high enantioselectivity.

PCN pincer palladium(II) complex catalyzed enantioselective hydrophosphination of enones: synthesis of pyridine-functionalized chiral phosphine oxides as NC(sp(3))O pincer preligands.

A series of chiral PCN pincer Pd(II) complexes VI-XIII with aryl-based aminophosphine-imidazoline or phosphinite-imidazoline ligands were synthesized and characterized. They were examined as enantioselective catalysts for the hydrophosphination of enones. Among them, complex IX, which features a Ph2PO donor as well as an imidazoline donor with (4S)-phenyl and N-Tol-p groups, was found to be the optimal catalyst. Thus, in the presence of 2-5 mol % of complex IX a wide variety of enones reacted smoothly with diarylphosphines to give the corresponding chiral phosphine derivatives in high yields with enantioselectivities of up to 98% ee. In particular, heteroaryl species such as 2-thienyl-, 2-furyl-, and 2-pyridinyl-containing enones that have a strong coordination ability to the Pd center were also appropriate substrates for the current catalytic system. For example, hydrophosphination of 2-alkenoylpyridines with diphenylphosphine followed by oxidation with H2O2 afforded the corresponding pyridine-functionalized chiral phosphine oxides in good yields with good to excellent enantioselectivities (10 examples, up to 95% ee). Furthermore, it had been demonstrated that the obtained pyridine-containing phosphine oxide acted as a tridentate ligand in the reaction with PdCl2 to form an intriguing NCsp(3)O pincer Pd(II) complex via Csp(3)-H bond activation, which to our knowledge is the first example of a chiral DCsp(3)D' Pd pincer (D ≠ D'; D and D' denote donor atoms such as P, N, etc.).

Phosphine oxide-catalyzed enantioselective intramolecular aldol reaction via regioselective enolization of unsymmetrical diketones with tetrachlorosilane.

The phosphine oxide-catalyzed asymmetric intramolecular aldol reactions of diketones were investigated. The combination of tetrachlorosilane and a chiral phosphine oxide catalyst promoted the acetyl-selective enolization of diketones, and the subsequent intramolecular aldol reaction occurred in an enantioselective manner. The introduction of two trimethylsilyl groups at the 4- and 4'-positions in BINAP dioxide catalyst improved the enantioselectivity. This reaction provides an effective synthetic method to access β-tertiary-hydroxy cyclohexanones in high yields and with high enantioselectivity.

ChemInform Abstract: Enantioselective Double Aldol Reactions Involving the Sequential Activation of Silicon Tetrachloride by Chiral Phosphine Oxides

AbstractReview: [23 refs.

ChemInform Abstract: Enantioselective Morita—Baylis—Hillman Reaction Catalyzed by a Chiral Phosphine Oxide.

AbstractA hypervalent silicon complex generated from a chiral phosphine oxide catalyst and SiCl4 reacts with vinyl ketones (I) to give the corresponding γ‐chloro silyl enol ether intermediates.

Enantioselective Double Aldol Reactions Involving the Sequential Activation of Silicon Tetrachloride by Chiral Phosphine Oxides

This account summarizes our recent studies on the development of phosphine oxide-catalyzed enantioselective double aldol reactions that extend hypervalent silicon chemistry by using a ­Lewis base catalyst. Chiral phosphine oxides repeatedly activate silicon ­tetrachloride and form hypervalent silicon complexes, thereby promoting sequential activation of substrates and realizing enantioselective double aldol reactions. The account describes several relevant applications of these reactions. 1 Introduction 2 General Concept of Sequential Catalysis by a Lewis Base 2.1 Lewis Base Catalysis with Chlorosilanes 2.2 Phosphine Oxides as Lewis Base Catalysts 3 Branched-Type Double Aldol Reactions 3.1 Enantioselective Branched-Type Double Aldol Reactions Catalyzed by Phosphine Oxides 3.2 Mechanism of the Branched-Type Double Aldol Reactions 3.3 Applications of the Branched-Type Double Aldol ­Reactions in Enantioselective Syntheses of 2,3-Dihydro­pyran-4-ones 4 Linear-Type Double Aldol Reactions 4.1 Enantioselective Linear-Type Double Aldol Reactions Catalyzed by Phosphine Oxides 4.2 Mechanism of the Linear-Type Double Aldol Reactions 4.3 Application of the Double Aldol Reactions to the Total Synthesis of (–)-Ericanone 5 Conclusions

Catalyst-free three-component reaction to synthesize chiral α-amino phosphine oxides

A novel method for high diastereoselective syntheses of chiral α-aminophosphine oxides by a three-component reaction involve a metal-free system was performed.