Novel sterically congested chiral tripodal phosphite ligands: catalytic asymmetric hydrosilylation of ketones with a Rh(I)–TRISPHOS catalyst

Pastor, Stephen D.; Shum, Sai P.

doi:10.1016/s0957-4166(98)00018-4

Cited by 32 publications

(10 citation statements)

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“…Metal Complexation . Previously we reported Rh(I) complexes of both 3 and ( S , S , S )- 7 , and their use as ligands for the hydrosilation of ketones . For both 3 and ( S , S , S )- 7 , the NMR spectral data are consistent with a metal complex in which two phosphorus atoms are bonded to Rh(I) and one phosphorus atom is noncoordinated .…”

Section: Resultsmentioning

confidence: 54%

“…Recently, we communicated the synthesis and utility of a chiral tripodal ligand, ( S , S , S )-TRISPHOS, an acronym for ( S , S , S )-tri{2,2‘,2‘ ‘-tris[(2,4,8,10-tetrakis(1,1-dimethylethyl)dibenzo[ d , f ][1,3,2]dioxaphosphepin-6-yl)oxy]propyl}amine [( S , S , S )- 7 ], in the Rh(I)-catalyzed asymmetric hydrosilation of ketones . ( S , S , S )- 7 is a sterically congested tripodal phosphite in which the phosphorus atom is bound in a seven-membered dibenzo[ d , f ][1,3,2]dioxaphosphepin ring (Figure ).…”

Section: Introductionmentioning

confidence: 99%

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Sterically Congested Tripodal Phosphites: Conformational Analysis, Solid-State Polymorphism, Metal Complexation, and Application to the Asymmetric Hydrosilation of Ketones¹

Shum¹,

Pastor²,

DeBellis³

et al. 2003

Inorg. Chem.

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The synthesis as well as isolation and crystallographic analysis of two solid-state polymorphs of the tripodal ligand tri[2,2',2' '-tris[(2,4,8,10-tetrakis(1,1-dimethylethyl)dibenzo[d,f][1,3,2]dioxaphosphepin-6-yl)oxy]ethyl]amine (3) is described. Form I crystallized from ethyl acetate in the space group P2(1)/n with the unit-cell parameters a = 20.070(10) A, b = 17.477(2) A, c = 27.620(3) A, and beta = 93.050(10) degrees, V = 9674.5(14) A(3), and Z = 4. Form II crystallized from a mixture of acetone and toluene in the space group P1 with the unit-cell parameters a = 12.493(1) A, b = 19.701(2) A, c = 21.027(2) A, alpha = 116.23(1) degrees, beta = 100.15(1) degrees, and gamma = 91.07(1) degrees, V = 4542 A(3), and Z = 2. Differences in the relative absolute stereochemistry of the stereoaxes in the seven-membered dibenzo[d,f][1,3,2]dioxaphosphepin ring are discussed. The synthesis and X-ray characterization of enantiomerically pure (S,S,S)-tri[2,2',2' '-tris[(2,4,8,10-tetrakis(1,1-dimethylethyl)dibenzo[d,f][1,3,2]dioxaphosphepin-6-yl)oxy]propyl]amine [(S,S,S)-7] are reported. Two crystallographically independent molecules exist in the unit cell that cannot be superimposed with each other by either a translation or a symmetry operation. The two solid-state conformers in the unit cell differed predominately by the absolute stereochemistry of the stereoaxes in the seven-membered dibenzo[d,f][1,3,2]dioxaphosphepin ring. The Rh(I)-catalyzed hydrosilation of acetophenone with the chiral ligands (R,R,S)-7 and (S,S,S)-7 showed significant differences in chiral induction. Chiral cooperativity between the stereoaxes and stereocenters in (S,S,S)-7 is observed. The mechanism of the communication between the stereocenters and stereoaxes leading to chiral cooperativity in the stereoselective transition state is suggested to be primarily steric in nature.

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Section: Resultsmentioning

confidence: 54%

Section: Introductionmentioning

confidence: 99%

Sterically Congested Tripodal Phosphites: Conformational Analysis, Solid-State Polymorphism, Metal Complexation, and Application to the Asymmetric Hydrosilation of Ketones¹

Shum¹,

Pastor²,

DeBellis³

et al. 2003

Inorg. Chem.

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“…203 A formally P,P,P,N-tetradentate ligand 130 was successfully employed in the Rh-catalysed hydrosilylation of acetophenone [reaction (5) and provided an ee of up to 81%]. 204 It should be emphasised that phosphite 130 coordinated to [RhCl(cod)] 2 behaves as a P,P-bidentate ligand. By and large there are a few phosphites that do not belong to the three major classes considered above.…”

Section: Other Groups Of Chiral Phosphite Ligandsmentioning

confidence: 99%

Chiral phosphites as ligands in asymmetric metal complex catalysis and synthesis of coordination compounds

Gavrilov¹,

Bondarev²,

Polosukhin³

2004

Russ. Chem. Rev.

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AlGaN/GaN/Si metal-insulator-semiconductor heterostructure field-effect transistors (MISHFETs) with SiN and Al 2 O 3 gate insulators are characterized by static and high-frequency measurements, and their performance is compared with nonpassivated and SiN-passivated heterostructure field-effect transistors (HFETs). The saturation drain current increased from ∼500 mA mm −1 for the HFETs to ∼770 mA mm −1 for the MISHFETs. The peak extrinsic transconductance of the MISHFETs (147 mS mm −1 for 8 nm SiN and 220 mS mm −1 for 4 nm Al 2 O 3 ) is higher than expected due to the increased gate-to-channel separation. Similarly, small signal microwave characterization yielded an increase in the current gain cut-off frequency (from 3.2 to 7.2 GHz) and the maximum frequency of oscillation (from 12.3 to 20.4 GHz) for the MISHFETs with 2 μm gate length compared to the HFET counterparts. Finally, the density of trap states, evaluated from the frequency-dependent conductance measurements, was ∼ =3 × 10 12 cm −2 eV −1 for the HFETs but only ∼ =1.8 × 10 12 cm −2 eV −1 for the MISHFETs. All of these demonstrate the capability of AlGaN/GaN MISHFETs of preparing high-performance and cost-effective devices for high-power microwave applications on a Si substrate.

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“…88 An example of a P donor ligand in the form of a sterically crowded phosphite ligand 18 possessing three branches linked by an amine core (termed TRISPHOS by the authors) has been shown to give 81% ee for the hydrosilylation of acetophenone using 2 mol% of catalyst. 89 The related hydrosilylation of C᎐ ᎐ N bonds has been extensively investigated by Buchwald who uses polymethylhydroxysilane (PMSH) in combination with his ethylene bridged chiral titanocene catalyst ({EBTHI}TiF 2 ) for the reduction of imines with up to 98% ee. 90 It is noted that the addition of primary amines to the reaction mixture assists in the release of product from the catalyst and thus improves the scope of this transformation.…”

Section: Hydrosilylationmentioning

confidence: 99%

Catalytic asymmetric processes

Tye

2000

J. Chem. Soc., Perkin Trans. 1

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Novel sterically congested chiral tripodal phosphite ligands: catalytic asymmetric hydrosilylation of ketones with a Rh(I)–TRISPHOS catalyst

Cited by 32 publications

References 35 publications

Sterically Congested Tripodal Phosphites: Conformational Analysis, Solid-State Polymorphism, Metal Complexation, and Application to the Asymmetric Hydrosilation of Ketones¹

Sterically Congested Tripodal Phosphites: Conformational Analysis, Solid-State Polymorphism, Metal Complexation, and Application to the Asymmetric Hydrosilation of Ketones¹

Chiral phosphites as ligands in asymmetric metal complex catalysis and synthesis of coordination compounds

Catalytic asymmetric processes

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Novel sterically congested chiral tripodal phosphite ligands: catalytic asymmetric hydrosilylation of ketones with a Rh(I)–TRISPHOS catalyst

Cited by 32 publications

References 35 publications

Sterically Congested Tripodal Phosphites: Conformational Analysis, Solid-State Polymorphism, Metal Complexation, and Application to the Asymmetric Hydrosilation of Ketones1

Sterically Congested Tripodal Phosphites: Conformational Analysis, Solid-State Polymorphism, Metal Complexation, and Application to the Asymmetric Hydrosilation of Ketones1

Chiral phosphites as ligands in asymmetric metal complex catalysis and synthesis of coordination compounds

Catalytic asymmetric processes

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Sterically Congested Tripodal Phosphites: Conformational Analysis, Solid-State Polymorphism, Metal Complexation, and Application to the Asymmetric Hydrosilation of Ketones¹

Sterically Congested Tripodal Phosphites: Conformational Analysis, Solid-State Polymorphism, Metal Complexation, and Application to the Asymmetric Hydrosilation of Ketones¹