Enantioselective Mukaiyama Aldol Reaction Research Articles

ChemInform Abstract: N‐Triflylthiophosphoramide Catalyzed Enantioselective Mukaiyama Aldol Reaction of Aldehydes with Silyl Enol Ethers of Ketones.

AbstractExcellent yields and good to excellent enantioselectivities are obtained for open‐chain silyl ethers (I) and (V).

A New Class of Ligands for Aqueous, Lanthanide-Catalyzed, Enantioselective Mukaiyama Aldol Reactions

The development of aqueous methods for generating enantiopure β-hydroxy carbonyl compounds is an important goal because these subunits compose many bioactive compounds and the ability to synthesize these groups in water has environmental and cost benefits. In this communication, we report a new class of ligands for aqueous, lanthanide-catalyzed, asymmetric Mukaiyama aldol reactions for the synthesis of chiral β-hydroxy ketones. Furthermore, we have used luminescence-decay measurements to unveil mechanistic information regarding the catalytic reaction via changes in water-coordination number. The precatalysts presented here yielded β-hydroxy carbonyls from aliphatic and aryl substrates with outstanding syn:anti ratios and enantiometric excesses of up to 49:1 and 97%, respectively.

ChemInform Abstract: Diastereoselective and Enantioselective Mukaiyama Aldol Reactions of α‐Ketoesters Using Hydrogen Bond Catalysis.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

N-triflylthiophosphoramide catalyzed enantioselective Mukaiyama aldol reaction of aldehydes with silyl enol ethers of ketones.

The first Brønsted acid catalyzed asymmetric Mukaiyama aldol reaction of aldehydes using silyl enol ethers of ketones as nucleophiles has been reported. A variety of aldehydes and silyl enol ethers of ketones afforded the aldol products in excellent yields and good to excellent enantioselectivities. Mechanistic studies revealed that the actual catalyst may be changed from the silylated Brønsted acid to the Brønsted acid itself depending on the reaction temperature.

Diastereoselective and enantioselective Mukaiyama aldol reactions of α-ketoesters using hydrogen bond catalysis

Hydrogen bond catalyzed Mukaiyama aldol reactions of alpha-ketoesters proceed in high diastereo- and enantioselectivities, giving products possessing two chiral centers, of which one is a tertiary alcohol.

ChemInform Abstract: Synthesis of Poly(Ethylene Glycol)—Supported (R)‐BINOL Derivatives and Their First Application in Enantioselective Mukaiyama Aldol Reactions.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

A Powerful Chiral Counteranion Motif for Asymmetric Catalysis

Room to swing a cat: A chiral disulfonimide has been designed as a powerful new motif for asymmetric catalysis. As a first illustration, a highly efficient and enantioselective Mukaiyama aldol reaction has been developed (see scheme). The actual catalyst is proposed to be an N-silyl imide which is generated in situ.

Synthesis of Poly(Ethylene Glycol)–Supported (R)-BINOL Derivatives and Their First Application in Enantioselective Mukaiyama Aldol Reactions

The Mukaiyama aldol reaction of 2-styryl-oxazole-4-carbaldehyde (1) as model substrate with S-ketene silyl acetal 2 catalyzed by poly(ethylene glycol)-supported binaphthyl-derived chiral titanium(IV) complexes afforded the corresponding aldol product in good to excellent yields and enantioselectivities up to 94% ee. The chemical yields and/or the enantioselectivities are enhanced by generating the active catalyst from Ti(OiPr)4, polymer-supported ligands (R)-6 or (R)-8, and chiral or achiral promoters. Pyrrolidine derivative (S)-13 and trifluoromethyl-substituted phenol 12 are the most efficient additives found.

Diastereoselective and enantioselective synthesis of tertiary alpha-hydroxy phosphonates through hydrogen-bond catalysis.

Hydrogen-bond activation by a diol promotes enantioselective Mukaiyama aldol reactions of acyl phosphonates. This mild and general method gives α-hydroxy phosphonate products having two chiral centers, one tertiary and one quaternary, formed with high diastereo- and enantioselectivity.

Comparison of immobilized Box and azaBox–Cu(II) complexes as catalysts for enantioselective Mukaiyama aldol reactions

Enantioselective Mukaiyama aldol reactions of different α-ketoesters was tested with copper complexes of chiral Box and azaBox ligands in both homogeneous and heterogeneous systems. Results in the homogeneous reactions were greatly influenced by the nature of the ketoester, the chiral ligand, and the reaction solvent. In the case of supported catalysts, the use of strongly coordinating azaBox ligands prevented the leaching of metal but reduced the Lewis acidity, and thus the catalytic activity, and did not solve the problem of poisoning by strong coordination of products, byproducts, or solvents. The counter-ion effect also was very significant, and electrostatic immobilization was efficient only with Box ligands (up to 86% ee at room temperature), whereas covalent immobilization allowed the use of azaBox ligands (up to 85% ee at room temperature) in the heterogeneous phase. Recovered deactivated solids could be reused in a reaction with a completely different mechanism that does not require acid centers, such as cyclopropanation.

Highly Diastereo‐ and Enantioselective Mukaiyama Aldol Reactions Catalyzed by Hydrogen Bonding.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Highly diastereo- and enantioselective Mukaiyama aldol reactions catalyzed by hydrogen bonding.

Enzyme lite: Like a minimalist enzyme, a simple chiral alcohol of the taddol family, 1, catalyzes Mukaiyama aldol reactions between silyl enolates of amides and aldehydes to afford products with high diastereo- and enantioselectivities (see scheme; TBS=tert-butyldimethylsilyl).

Highly Diastereo‐ and Enantioselective Mukaiyama Aldol Reactions Catalyzed by Hydrogen Bonding

Ein abgespecktes Enzym: Wie ein minimalistisches Enzym katalysiert ein einfacher chiraler Alkohol aus der Taddol-Familie (1) die hoch diastereo- und enantioselektiven Mukaiyama-Aldolreaktionen zwischen Silylenolaten von Amiden und Aldehyden (siehe Schema, TBS=tert-Butyldimethylsilyl). Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2001/2006/z601638_s.pdf or from the author. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Catalytic Enantioselective Mukaiyama Aldol Reaction via a Chiral Indium(III)—Pybox Complex.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Multipurpose box‐ and azabox‐Based Immobilized Chiral Catalysts

AbstractAzabis(oxazolines) can be used as chiral ligands in the copper‐catalyzed enantioselective Mukaiyama aldol reaction. When supported on solids, azabis(oxazoline)‐copper complexes are more easily deactivated than their analogous bis(oxazoline)‐copper complexes, and are not compatible with the use of coordinating solvents in the method of preparation. The performance of the immobilized catalysts (up to 86 % ee) depends on the support and the reaction solvent, with some positive effect on enantioselectivity due to surface effects. The deactivation is not irreversible and the deactivated catalysts show excellent performance in the cyclopropanation reaction, providing added value to the supported multipurpose catalysts.

Catalytic enantioselective Mukaiyama aldol reaction via a chiral indium(III)–pybox complex

A chiral indium(III) complex prepared from indium triflate and a pybox ligand has been developed to give good yields and enantioselectivities (up to 92% ee) in the addition of (1-methoxy-2-methyl-propenyloxy)-trimethylsilane to various aromatic and aliphatic aldehydes via the Mukaiyama aldol reaction.

Dirhodium(II) Tetrakis[N-benzene-fused Phthaloyl-(S)-piperidinonate] as a Chiral Lewis Acid: Catalytic Enantioselective Aldol Reactions of Acetate-derived Silylketene Acetals and Aldehydes

A first example of chiral dirhodium(II) complex-catalyzed enantioselective Mukaiyama aldol reactions is described. The aldol addition reaction of methyl acetate-derived trimethylsilylketene acetal with specific aldehydes such as benzyloxyacetaldehyde and electron-poor aromatic aldehydes is effectively catalyzed by dirhodium(II) tetrakis[N-benzene-fused phthaloyl-(S)-piperidinonatel (la), providing silylated aldol adducts in up to 94% ee.

Highly Enantioselective Mukaiyama Aldol Reaction of α,α‐Dichloro Ketene Silyl Acetal: An Efficient Synthesis of a Key Intermediate for Diltiazem.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Highly enantioselective mukaiyama aldol reaction of alpha,alpha-dichloro ketene silyl acetal: an efficient synthesis of a key intermediate for diltiazem.

An efficient synthesis of methyl (2R,3S)-3-(4-methoxyphenyl)glycidate (-)-2, a key intermediate for diltiazem (1), has been developed on the basis of the highly enantioselective Mukaiyama aldol reaction of p-anisaldehyde (4a) with alpha,alpha-dichloro ketene silyl acetal 5. Thus, the reaction using a stoichiometric amount of chiral oxazaborolidinone catalyst 12a proceeded to excellent yield (83%) and high enantioselectivity (96% ee), together with the chiral ligand 13a in nearly quantitative recovery. The reaction using a substoichiometric amount of 12e (20 mol %) also proceeded to excellent yield (88%), with somewhat lower enantioselectivity (77% ee). The aldol product 3a thus obtained was easily converted to (-)-2 in excellent yield (80%) and high optical purity (>99% ee). The highly enantioselective Mukaiyama aldol reaction with 5 catalyzed by 12a proved to be applicable to various aldehydes. An efficient preparation of 5 from inexpensive starting materials was also described.

An Insoluble Polymer-Bound Bis-Oxazoline Copper(II) Complex: A Highly Efficient Heterogeneous Catalyst for the Enantioselective Mukaiyama Aldol Reaction.

The polystyrene-supported bis-oxazoline 1 forms a complex with copper(II)triflate that is a highly effective catalyst for the heterogeneously catalyzed enantioselective Mukaiyama aldol reaction of silylthioketene acetals with methyl pyruvate (ca. 90 % yield, ca. 90 % ee). The catalyst can be recovered by simple filtration and reused several times without a decline in enantioselectivity.