Asymmetric conjugate addition of diethyl zinc to enones with chiral phosphorus ligands derived from TADDOL

Alexakis, Alexandre; Vastra, J.; Burton, Jonathan W.; Benhaim, Cyril; Mangeney, Pierre

doi:10.1016/s0040-4039(98)01761-4

Cited by 118 publications

(22 citation statements)

References 23 publications

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“…The autoclave was allowed to cool to room temperature, and then the gases were carefully released. The solvent was removed and the crude reaction mixture was subjected to 1 H NMR for determination of the conversion and the branched-to-linear ratio of the resulting aldehydes 8. To the aldehyde mixture, (S)-methylbenzylamine (130 l) and anhydrous MgSO 4 were added, and the mixture was stirred at room temperature for 1 h. The solid was filtered off, and the solution was concentrated in vacuo to give the corresponding diastereomeric mixture of aldimines.…”

Section: Methodsmentioning

confidence: 99%

“…To the aldehyde mixture, (S)-methylbenzylamine (130 l) and anhydrous MgSO 4 were added, and the mixture was stirred at room temperature for 1 h. The solid was filtered off, and the solution was concentrated in vacuo to give the corresponding diastereomeric mixture of aldimines. The enantioselectivity was determined by 1 verting the compound to 4-methyldihydrofuran-2-one (24), followed by the measurement of its specific optical rotation.…”

Section: Methodsmentioning

confidence: 99%

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New biphenol-based, fine-tunable monodentate phosphoramidite ligands for catalytic asymmetric transformations

Hua

Vassar

Choi

et al. 2004

Proc. Natl. Acad. Sci. U.S.A.

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Monodentate phosphoramidite ligands have been developed based on enantiopure 6,6-dimethylbiphenols with axial chirality. These chiral ligands are easy to prepare and flexible for modifications. The fine-tuning capability of these ligands plays a significant role in achieving high enantioselectivity in the asymmetric hydroformylation of allyl cyanide and the conjugate addition of diethylzinc to cycloalkenones. R ecently, chiral monodentate phosphorus ligands (phosphites, phosphoramidites, and phosphonites) have been attracting considerable interest for their use in catalytic asymmetric synthesis, because the chiral catalysts bearing these ligands have proven to be highly efficient in various asymmetric reactions. This is a previously univestigated wave in the design of chiral ligands, which makes a sharp contrast to almost three decades of predominance by C2 symmetrical bidentate phosphorus ligands for a variety of catalytic asymmetric transformations. This wave of designing simple and readily modifiable chiral structures, which are easy to synthesize, is fitting very well to the trendy and highly practical combinatorial approaches to the development of the most suitable chiral ligand for a particular catalytic asymmetric process of commercial value or academic interest. This approach is currently considered most practical rather than trying to develop a universal and almighty chiral ligand for different types of catalytic asymmetric transformations.Before the launch of our research program on the development of chiral monodentate phosphorus ligands based on enantiopure 2,2Ј-dihydroxy-6,6Ј-dimethylbiphenyls, by far, the most studied monodentate ligands were phosphites and phosphoramidites based on TADDOL (1) (1) BINOL (2) (2-4), a spirobiindanediol (3) (5), or an achiral biphenol (4) (6, 7) bearing a chiral or achiral secondary alcohol or amine (Fig. 1). These ligands have found a wide range of applications in metalcatalyzed asymmetric transformations such as hydrogenation (5, 8-10), 1,4-additions of dialkylzinc (11, 12) and boronic acids (13) to enones, hydrovinylation (14), hydrosilylation (15), intramolecular Heck reaction (16), hydroformylation (17), allylic alkylation (18, 19), amination (20), and etherification (21).We have been developing a previously uninvestigated class of chiral monodentate phosphite and phosphoramidite ligands, 5 and 6, from readily accessible enantiopure, axially chiral biphenyls ( Fig. 2) and have recently published the successful application of chiral monophosphite ligands 5 to the Rh(I)-catalyzed asymmetric hydrogenation of dimethyl itaconate (Fig. 2) (22).One of the salient and practical features of these chiral monophosphite ligands is the fine-tuning capability with modifiable substituents R 1 , R 2 , and R 3 in the formula 5. This fine-tuning capability of ligands 5 (phosphites) and 6 (phosphoramidites) is expected to play a crucial role in the application of these ligands to a variety of catalytic asymmetric reactions. In fact, we have demonstrated that the substituents (R 2 )...

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

New biphenol-based, fine-tunable monodentate phosphoramidite ligands for catalytic asymmetric transformations

Hua

Vassar

Choi

et al. 2004

Proc. Natl. Acad. Sci. U.S.A.

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“…All chiral ligands were prepared according to the literature procedures (for ligands L1-L11, see references [26], [33], [47], and [48]; for ligands L12-L15, see references [49] and [50]; for ligands L16-L19, see reference [31]). Lithium bromide and lithium chloride were dried at 80 8C over 24 h prior to use.…”

Section: Methodsmentioning

confidence: 99%

Enantioselective Iridium‐Catalyzed Allylic Arylation

Polet

Rathgeb

Falciola

et al. 2009

Chemistry A European J

104

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We describe herein the development of the first iridium-catalyzed allylic substitution using arylzinc nucleophiles. High enantioselectivities were obtained from the reactions, which used commercially available Grignard reagents as the starting materials. This methodology was also shown to be compatible with halogen/metal exchange reactions. Its synthetic potential is demonstrated by its application towards the formal synthesis of (+)-sertraline.

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“…iv) In contrast to the results obtained with monodentate phosphites derived from TADDOL [7], replacement of the Ph by naphthalen-2-yl groups in the diarylmethoxy positions (ligand 7e) led to a decrease of selectivity (Entry 5) 7 ). v) The temperaturedependence is rather small: at lower temperature a slightly better enantioselectivity was observed 8 ), while, at ambient temperature, the enantioselectivity was poorest, and, furthermore, 5% of silylenol ether was formed as a by-product (detected by 1 H-NMR spectroscopy) 9 ). vi) Using toluene as solvent gave slightly higher enantiomer ratios, as Helvetica Chimica Acta ± Vol.…”

Section: Methodsmentioning

confidence: 99%

“…The preparation of the first examples of this class of compounds 2 (R' aryl, aryloxy) and their application to Rh I -catalyzed enantioselective reactions have been described previously [7]. Also, the combination with chiral alcohols and amines ( R' in 2) led to ligands which were used in conjugate additions of Et 2 Zn to a,b-unsaturated carbonyl compounds [8]. However, it is well-known that enantioselective catalysis is generally more efficient with bidentate than with monodentate ligands (for reviews, see [9]).…”

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confidence: 99%

Catalytic Enantioselective Hydrosilylation of Ketones with Rhodium-Phosphite Complexes Containing a TADDOLate and a Dihydrooxazole Unit

Heldmann¹,

Seebàch²

1999

HCA

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New types of chiral phosphorus/nitrogen ligands, capable of forming six‐membered‐ring metal chelates have been prepared from α,α,α′,α′‐tetraaryl‐1,2‐dioxolane‐4,5‐dimethanols (TADDOLs), PCl3, and dihydrooxazole alcohols (from amino acids) (7 in Scheme 1). The X‐ray crystal structure of a Rh complex of one of these ligands, 8b, has been determined (Scheme 2 and Fig.). Enantioselective hydrosilylations of dialkyl and aryl alkyl ketones with Ph2SiH2/0.01 equiv. RhI⋅7 have been studied and found to provide secondary alcohols in enantiomer ratios of up to 97 : 3 (Scheme 3 and Table). The ligand prepared from (R,R)‐TADDOL and the (R)‐valine‐derived (R)‐α,α‐dimethyl‐4‐isopropyl‐4,5‐dihydrooxazole‐2‐methanol gives better results than the (R,R,S)‐isomer (7d vs. 7c in Scheme 3), and an i‐Pr group on the 4,5‐dihydrooxazole ring gives rise to a slightly better selectivity than a Ph group. With the (R,R,R)‐ligands the hydrogen transfer occurs from the Re face of the oxo groups (Scheme 4).

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Asymmetric conjugate addition of diethyl zinc to enones with chiral phosphorus ligands derived from TADDOL

Cited by 118 publications

References 23 publications

New biphenol-based, fine-tunable monodentate phosphoramidite ligands for catalytic asymmetric transformations

New biphenol-based, fine-tunable monodentate phosphoramidite ligands for catalytic asymmetric transformations

Enantioselective Iridium‐Catalyzed Allylic Arylation

Catalytic Enantioselective Hydrosilylation of Ketones with Rhodium-Phosphite Complexes Containing a TADDOLate and a Dihydrooxazole Unit

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