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Amino-alcohols enantioselective formation

Hydrogenation of a series of /Z-isomeric mixtures of a-arylenamides with a MOM-protected /3-hydroxyl group catalyzed by a BICP-Rh complex or an Me-DuPhos complex leads to the formation of chiral /3-amino alcohol derivatives with excellent enantioselectivities.70b A 1,4-diphosphane 26 with a rigid 1,4-dioxane backbone is also very effective for this transformation (Equation (28)).76 DIOP -Rh72a and Me-DuPhos-Rh219 catalysts are also effective for this transformation. [Pg.28]

Enantioselective reduction of ketones.1 The ability of diborane in combination with the vic-amino alcohol (S)-2-amino-3-methyl-l,l-diphenyl-l-butanol (12, 31) to effect enantioselective reduction of alkyl aryl ketones involves formation of an intermediate chiral oxazaborolidine, which can be isolated and used as a catalyst for enantioselective borane reductions (equation I). [Pg.239]

The first report in this regard described a method for direct formation of the desired optically active (S)-alcohol 32a, via enantioselective reduction with a chiral amine complex of lithium aluminum hydride (Scheme 14.9). Therefore, the necessary chiral hydride complex 38 was preformed in toluene at low temperature from chiral amino alcohol 37. The resulting hydride solution was then immediately combined with ketone 31 to afford the desired (S)-alcohol 32a in excellent yield and enantiomeric excess. In addition to providing a more efficient route to the desired drug molecule, this work also led to the establishment of the absolute configuration of duloxetine (3) as S). [Pg.208]

Use of hydroxyacetone as donor in the asymmetric Mannich reaction led to the formation of optically active syn /i-amino alcohols bearing two stereogenic centers [22, 23], In the presence of 35 mol% L-proline as organocatalyst several types of syn / -amino alcohol syn-35 were successfully synthesized with enantioselectivity up to 99% ee and high diastereomeric ratio. For example, a high yield of 92%, a diaster-eomeric ratio of 20 1, and enantioselectivity >99% ee were observed by List et al. for formation of the syn yfi-amino alcohol 35a (Scheme 5.17) [23]. In addition to hydroxyacetone the methylated derivative methoxyacetone was also applied successfully in this reaction (93% yield, d.r. > 39 1, >99% ee). [Pg.101]

R-(R, S )]-p-Methyl-a-phenyl-1-pyrrolidineethanol is an important chiral mediator for the enantioselective addition of an acetylide to a prochiral ketone.2 3 This reaction has been successfully applied to the synthesis of the reverse transcriptase inhibitor efavirenz (DMP-266) (Scheme 1).3.4 Preparation of the enantiomer, (1S,2R)-N-pyrrolidinylnorephedrine, has been reported.2 The method used potassium carbonate (K2CO3) as base, but the yield of the product was only 33%. The submitters have extensively studied the formation of the pyrrolidinyl ring under various conditions as summarized in Table I. Eventually they found that the reaction was extremely efficient when it was run in toluene using sodium bicarbonate (NaHCC>3) as base (entry 8, Table I),5 which gave [R-(R, S )]-p-methyl-a-phenyl-1-pyrrolidineethanol quantitatively. Enantioselective (up to 99% ee) addition of cyclopropylacetylene to the ketoaniline 1 is achieved when the solution of [R-(R, S )]-p-methyl-a-phenyl-1-pyrrolidineethanol is used as a chiral additive.3 In addition, this method is also applicable to the preparation of a variety of alkylated norephedrines and other amino alcohols in excellent yields as Illustrated in Table II. These amino alcohols are potentially useful in asymmetric syntheses. [Pg.195]

The formation of stereogenic C-N bonds by hydrogenation of the enamine structure is not only limited to amino acids. Likewise, chiral 1,2-aminoalcohols or 1,2-diamines can be produced by the enantioselective hydrogenation of dehydro-p-amino alcohols (or their esters) and of dehydro-a-amino aldoximes, respectively (eq 6 and eq 7, Thble 2). Esters and aldoximes thus obtained can be converted into the corresponding alcohols or diamines by standard methods. By this means, simple amines with one aryl group attached to the double bond can also be hydrogenated with high enantioselectivity. ... [Pg.121]

The asymmetric reduction of aryl ketone can be achieved with ruthenium catalysts (Scheme 24), prepared separately or in situ by formation of [RuCl2(arene)]2 and ligand, in z-PrOH [81]. The high enantioselectivities and rate are very dependent upon the functionality of the substrate, T -arene and A -substitution of the diamino or amino alcohol ligands on ruthenium [81]. The hydrogen transfer reaction in z-PrOH is reversible, necessitating low concentrations, while extensive... [Pg.168]

Since the formation of a chiral lithium alkoxide is likely to be involved in the asymmetric addition process, various ratios of the components (chiral ligand -BuLi 5a) were examined. The results of this study revealed a remarkable solvent effect on both efficiency and selectivity for -BuLi additions, and a dependence of the absolute configuration of the amine 6 on the solvent employed. The amino alcohols such as 7 and 8 gave only poor enantioselectivities in the butyl addition... [Pg.882]

The simple amino alcohols discussed have been used as catalysts for enantioselective addition of zinc alkyls to carbonyl compounds (Section D. 1.3.1.4.). In most cases, the reactive amino function is used for the formation of derivatives (including hcterocycles. such as dihydrooxa-zoles. which are formed with acids) which are useful as sources of chiral carbanions (see Sections C., D.l.1.1.2., D.l.3.1.4., D.l.6.1.2.1.. D.1.6.1.3., D.1.6.1.5., D.2.1. and D.2.3.I.). [Pg.29]

These 0,A-dialkylated amino alcohols are used as the lithium salts for enantioselective deprotonation and elimination reactions (Section C.), and for the formation of enamines used in Michael-type additions of azaenolates (Section D.1.5.2.4.). [Pg.34]


See other pages where Amino-alcohols enantioselective formation is mentioned: [Pg.459]    [Pg.168]    [Pg.175]    [Pg.271]    [Pg.30]    [Pg.49]    [Pg.145]    [Pg.97]    [Pg.9]    [Pg.123]    [Pg.99]    [Pg.17]    [Pg.630]    [Pg.1638]    [Pg.271]    [Pg.232]    [Pg.176]    [Pg.34]    [Pg.169]    [Pg.79]    [Pg.817]    [Pg.959]    [Pg.110]    [Pg.113]    [Pg.100]    [Pg.74]    [Pg.240]    [Pg.97]    [Pg.361]    [Pg.287]    [Pg.279]    [Pg.862]    [Pg.259]    [Pg.259]    [Pg.113]    [Pg.196]    [Pg.20]    [Pg.1174]    [Pg.45]    [Pg.384]   
See also in sourсe #XX -- [ Pg.563 ]




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Alcohols enantioselective

Alcohols formation

Amino alcohols

Amino alcohols, formation

Amino formation

Enantioselectivity alcohols

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