Catalytic Borane Reduction Research Articles

Practical Enantioselective Reduction of Ketones Using Oxazaborolidine Catalysts Generated In Situ from Chiral Lactam Alcohols.

Oxazaborolidine catalyst (CBS catalyst) has been extensively used for catalytic borane reduction with a predictable absolute stereochemistry and high enantioselectivity. However, the use of isolated CBS catalyst sometimes has the drawback of low reproducibility due to the aging of the CBS catalyst during storage. Therefore, we investigated a more reliable and practical method for the reduction of a variety of ketones including challenging substrates, primary aliphatic ketones, α,β-enones, and trifluoromethyl ketones. This review surveys the developments in borane reduction using oxazaborolidine catalysts generated in situ from chiral lactam alcohols and borane.

ChemInform Abstract: Enantioselective Catalytic Borane Reductions of Achiral Ketones: Syntheses and Application of Two Chiral β-Amino Alcohols from (S)- 2-Indoline Carboxylic Acid.

ChemInform 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.

ChemInform Abstract: Enantioselective Catalytic Borane Reductions of Achiral Ketones: Synthesis and Application of New Chiral β-Amino Alcohols from L- Methionine.

Abstract The in situ formed chiral oxazaborolidine catalysts from optically active β-amino alcohols 1-3 from L-methionine ethyl carboxylate 4 have been used successfully in the enantioselective catalytic homogenous borane reductions of various aromatic ketones. The corresponding optically active alcohols are obtained in high optical purity (up to 100% ee ).

Asymmetric Borane Reduction of Prochiral Ketones Catalyzed by Phosphinamides Prepared from L‐Serine.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Asymmetric borane reduction of prochiral ketones catalyzed by phosphinamides prepared from L‐serine

AbstractSynthesis of several new chiral phosphinamide catalysts with a proximal hydroxyl group from L‐serine was described. These compounds have been successfully used in the asymmetric catalytic borane reduction of prochiral ketones. The optically active secondary alcohols were obtained with an enantiomeric excess (ee) up to 81% and excellent yields. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:288–291, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10145

Enantio- and diastereoselective synthesis of all four stereoisomers of formoterol

Enantioselective syntheses of all four stereoisomers of formoterol are accomplished using asymmetric catalytic borane reductions with chiral oxazaborolidines as reducing agents.

Molecular-level chiral discrimination and induction

The review describes the mechanism of chiral discrimination of racemic amines upon crystallization and the induction of chirality in organic reactions by using them as chiral auxiliaries. In order to form conglomerates, which can be resolved into the two enantiomers upon alternative seeding, both formation and packing of 21-columns are essentially very important. On the other hand, in order to achieve high efficiency in resolution through diastereomeric salt formation, which is the most practical method, one of a pair of diastereomeric salts derived from a racemic amine and an enantiomerically pure resolving agent should at least have two 21-columns and planar boundary surfaces in its crystal structure. On the basis of this knowledge, we developed several artificial chiral auxiliaries such as erythro-2-amino-1,2-diphenylethanol,cis-2-amino-1-acenaphthenol, andcis-2-amino-3,3-dimethyl-1-indanol. These were found to be very efficient chiral auxiliaries in asymmetric inductions: alkylation of chiral imines, catalytic borane-reduction, and alkylation of chiral N-acylated oxazolidinone.

Enantioselective Catalytic Borane Reduction of Prochiral Ketones: Synthesis and Application of New Rigid β-Amino Alcohols with a Cycloalkanol Subunit

Abstract Enantiocontrolled reduction of prochiral ketones with borane in the presence of new enantiomerically pure bi-and tricyclic β-sec-amino alcohols 2–5 as stereodifferentiating catalysts afforded the optically active corresponding secondary alcohols in moderate to excellent (up to 98 % op) optical yields.

ChemInform Abstract: Enantioselective Catalytic Borane Reductions of Achiral Ketones: Synthesis and Application of New Rigid Catalysts Prepared from (R)‐ Phenylglycine and (S)‐Phenylalanine.

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.

Enantioselective Catalytic Borane Reductions of Achiral Ketones: Synthesis and Application of New Rigid Catalysts Prepared from (R)-Phenylglycine and (S)-Phenylalanine

Abstract Exnantiocontrolled reduction of prochiral ketones with borane in the presence of homochiral amino alcohols 1 - 4 as enantioselective catalysts afforded the chiral corresponding secondary alcohols in moderate to high (55 to 88 %) optical yields.

ChemInform Abstract: Enantioselective Catalytic Borane Reductions of Achiral Ketones: Synthesis and Application of New Catalysts Prepared from (S)‐tert‐ Leucine and (S)‐Azetidinecarboxylic Acid.

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.

Enantioselective catalytic borane reductions of achiral ketones: Synthesis and application of new chiral β-amino alcohols from L-methionine

The in situ formed chiral oxazaborolidine catalysts from optically active β-amino alcohols 1-3 from L-methionine ethyl carboxylate 4 have been used successfully in the enantioselective catalytic homogenous borane reductions of various aromatic ketones. The corresponding optically active alcohols are obtained in high optical purity (up to 100% ee).

ChemInform Abstract: Enantioselective Catalytic Borane Reductions of Aromatic Ketones. Syntheses and Application of Two Chiral β‐Amino Alcohols from (S)‐ Porretine.

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.

Enantioselective catalytic borane reductions of achiral ketones: Syntheses and application of two chiral β-amino alcohols from ( S)-2-indoline carboxylic acid

The synthesis of ( S)-α,α-diphenyl-(indolin-2-yl)methanol 1 makes available the chiral oxazaborolidine 2 which is an excellent catalyst for borane reduction of prochiral ketones to chiral secondary alcohols, e.g. acetophenone, in high optical purity The new chiral auxiliary 1 is sythesized from ( S)-2-indoline carboxylic acid in a two step procedure. ( S)-(Indolin-2-yl)methanol 3 is converted to the oxazaborolidine 4 which served also as an enantioselective catalyst in the reduction of aromatic ketones with BH 3·THF.

Enantioselective catalytic borane reductions of aromatic ketones: Syntheses and application of two chiral β-amino alcohols from ( S)-porretine

The in situ formed chiral oxazaborolidine catalysts from two optically active β-amino alcohols ( S)- 1 and ( S)- 2 from benzyl ( S)-1,2,3,4-tetrahydroisoquinoline-3-carboxylate ( S)- 3 have been used sucessfully in the enantioselective catalytic homogenous borane reductions of various aromatic ketones.