Search results for "enantioselective synthesis"

ChemInform Abstract: Asymmetric Synthesis Using Polymer-Immobilized Proline Derivatives

2012

ChemInform Abstract: Highly Enantioselective Protonation of the 3,4-Dihydro-2-methylnaphthalen-1(2H)-one Li-Enolate by TADDOLs.

2001

A series of nine TADDOLs (=α,α,α′,α′-tetraaryl-1,3-dioxolane-4,5-dimethanols) 1a – 1i, have been tested as proton sources for the enantioselective protonation of the Li-enolate of 2-methyl-1-tetralone (=3,4-dihydro-2-methylnaphthalen-1(2H)-one). The enolate was generated directly from the ketone (with LiN(i-Pr)2 (LDA)/MeLi) or from the enol acetate (with 2 MeLi) or from the silyl enol ether (with MeLi) in CH2Cl2 or Et2O as the solvent (Scheme). The Li-enolate (associated with LiBr/LDA, or LiBr alone) was combined with 1.5 – 3.0 equiv. of the TADDOL at −78° by addition of the latter or by inverse addition. 2-Methyl-1-tetralone of (S)-configuration is formed (≤80% yield) with up to 99.5% sele…

Asymmetric Synthesis of Spiro Tetrahydrothiophene-indan-1,3-diones via a Squaramide-Catalyzed Sulfa-Michael/Aldol Domino Reaction

2016

Synthesis 48(08), 1131-1138(2016). doi:10.1055/s-0035-1560412

Vergleichende dimerisierung der enantiomere von Oct-1-in-3-ol mit chiralen rhodium-phosphan-komplexen

1996

Abstract Three optically active phosphanes ([(S)-2-methylbutyl]3−nP[phenyl]n(n = 0, 1, 2), were tested as ligands in rhodium(I) complexes to form catalysts for the enantioselective dimerisation of (R)- and (S)-oct-1-yn-3-ol. The catalytic reaction provides enantioselectivity for this type of CC bond formation. For reactions at 45–75°C and depending on the P-ligand used the rates vary for both enantiomers from 6:1 to 50:1 in favour of the (S)-octynol.

Asymmetric synthesis of fluorinated cyclic beta-amino acid derivatives through cross metathesis.

2006

The asymmetric synthesis of several fluorinated cis-2-aminocycloalkane carboxylic acids (cis-2-ACACs) with a cross metathesis (CM) reaction as the key step has been carried out, constituting the first time a metathesis protocol has been undertaken with fluorinated imidoyl chlorides. Subsequent chemoselective hydrogenation of the olefin moiety, Dieckmann condensation, and stereoselective reduction of the iminic double bond afforded the corresponding beta-amino esters with several ring sizes. The asymmetric version of the process was achieved by using (-)-8-phenylmenthol as a chiral auxiliary.

Stereoselective synthesis of perillaldehyde-based chiral β-amino acid derivatives through conjugate addition of lithium amides.

2014

The Michael addition of dibenzylamine to (+)-tert-butyl perillate (3) and to (+)-tert-butyl phellandrate (6), derived from (S)-(−)-perillaldehyde (1), resulted in diastereomeric β-amino esters 7A–D in a moderately stereospecific reaction in a ratio of 76:17:6:1. After separation of the diastereoisomers, the major product, cis isomer 7A, was quantitatively isomerized to the minor component, trans-amino ester 7D. All four isomers were transformed to the corresponding β-amino acids 10A–D, which are promising building blocks for the synthesis of β-peptides and 1,3-heterocycles in three steps. The steric effects of the isopropyl group at position 4 and of the α-methyl substituent of (R)-N-benzyl…

ChemInform Abstract: Total Synthesis of (+)-Greek Tobacco Lactone.

2015

An enantioselective, protecting-group-free, total synthesis of (+)-Greek tobacco lactone has been achieved by using an organocatalytic Mukaiyama–Michael reaction and a stereospecific oxa-Michael reaction as key steps.

Total Synthesis of (+)-Greek Tobacco Lactone

2014

An enantioselective, protecting-group-free, total synthesis of (+)-Greek tobacco lactone has been achieved by using an organocatalytic Mukaiyama–Michael reaction and a stereospecific oxa-Michael reaction as key steps.

ChemInform Abstract: Stereoselective Synthesis of α-Arylalkylamines by Glycosylation-Induced Asymmetric Addition of Organometallic Compounds to Imine…

2009

Arylalkylamines are of interest as building blocks for the synthesis of biologically active compounds and as chiral ligands or chiral auxiliaries in stereoselective syntheses [1]. Their stereoselective synthesis has been achieved by enantioselective reduction of ketimines using chiral reagents [2], as for example Corey’s oxaborolidines [3], or proline-derived triacyloxyborohydrides [4]. Particularly efficient asymmetric syntheses of chiral arylalkylamines have been accomplished by Noyori et al. [5] through enantioselective catalysis of hydrogen transfer reactions using a chiral 1,2-diphenyl-ethylenediamine ruthenium catalyst. Enantioselective transferhydrogenationshave also been achieved us…

Stereoselective Synthesis of α-Arylalkylamines by Glycosylation-induced Asymmetric Addition of Organometallic Compounds to Imines

2009

Arylalkylamines are of interest as building blocks for the synthesis of biologically active compounds and as chiral ligands or chiral auxiliaries in stereoselective syntheses [1]. Their stereoselective synthesis has been achieved by enantioselective reduction of ketimines using chiral reagents [2], as for example Corey’s oxaborolidines [3], or proline-derived triacyloxyborohydrides [4]. Particularly efficient asymmetric syntheses of chiral arylalkylamines have been accomplished by Noyori et al. [5] through enantioselective catalysis of hydrogen transfer reactions using a chiral 1,2-diphenyl-ethylenediamine ruthenium catalyst. Enantioselective transferhydrogenationshave also been achieved us…