Search results for "Stereoselective synthesis"

Ligands P-stéréogéniques dérivés du calix[4]arène. Synthèses et applications en catalyse asymétrique

2010

We were interested in synthesis of P-stereogenic ligands derived from calix[4]arene and in their application in asymmetric catalysis. Mono et diphosphines were prepared on the upper rim of the macrocyle starting from the mono or dianion of the calix[4]arene and chlorophosphines borane or the oxazaphospholidine borane complex. The best selectivity was obtained by reaction of the dianion with the oxazaphospholidine borane complex leading to a bisaminophosphine borane. After acidolysis with HCl giving the corresponding bischlorophosphine and reaction with organolithium reagents, diphosphines diborane were obtained with good yields (40 à 60 %). X-ray structures of the prepared ligands confirmed…

Stereoselective synthesis and application of tridentate aminodiols derived from (+)-pulegone

2016

Abstract A library of tridentate aminodiols, derived from naturally occurring (R)-(+)-pulegone, was synthesized and applied as chiral catalysts in the addition of diethylzinc to benzaldehyde. The reduction of pulegone furnished pulegol, which was transformed into allylic trichloroacetamide via Overman rearrangement of the corresponding trichloroacetimidate. The protected enamine was subjected to dihydroxylation with OsO4/NMO system resulting in a 1:1 mixture of (1R,2R,4R)- and (1S,2S,4R)-aminodiol diastereomers. After the removal of the trichloroacetyl protecting groups, the obtained primary aminodiols were transformed into secondary ones. The regioselectivity of the ring closure of the N-b…

Stereoselective synthesis: from organoselenium to organocatalysis

Proline- and prolinamide-supported polystyrene: powerful and highly recyclable organocatalysts for the asymmetric aldol reaction

2009

Diastereoselective Synthesis of 2-Phenylselenenyl-1,3-anti-Diols and 2-Phenylselenenyl-1,3-anti-Azido-Alcohols via Hydroxy- and Azido-Selenenylation …

2005

A method to synthesize 2-phenylselenenyl-1,3-anti-diols and 2-phenyl- selenenyl-1,3-anti-azidoalcohols via hydroxy- or azido-selenenylation of trans-allylic alcohols is reported. Moreover, the first example of hydroxyl-selenenylation of an allylic azide is presented. Yields ranging from moderate to good and diastereomeric ratios up to 95:5 are achieved.

Experimental and theoretical investigations for the regio and stereoselective transformation of trans 1,2,3-trisubstituted aziridines into trans oxaz…

2003

The regio and stereoselective transformation of trans 1,2,3-trisubstituted aziridines into trans oxazolidin-2-ones takes place in good yield. However, the cis configuration at C2 and C3 in monocyclic aziridines is a limiting factor for this transformation. Ab initio calculations show that while the ring-opening process assisted by iodide is regioselective, the subsequent ring-closure is responsible for the retention of the configuration at the trans oxazolidin-2-ones. The larger energy found for the ring-closure process for the cis aziridines accounts for the non-formation of the cis oxazolidin-2-ones.

SINTESI STEREOSELETTIVA IN IONO-EUTECTOGEL SUPRAMOLECOLARI

2021

Phospholylmethano P-chirogenic-phosphine-borane as P-(η2-BH3)-chelating ligands of rhodium (I): Synthesis, characterization and asymmetric hydrogenat…

2021

International audience; The stereoselective synthesis of new phospholylmethano P-chirogenic-phosphine-borane was achieved by P-C bond formation of the bridge, using electrophilic or nucleophilic P*-building blocks. These P1CH2P2*.BH3 ligands behaved as chelating (κ1-P1)-(η2-BH3) entities towards the cationic rhodium(I) centre. The resulting chiral rhodium complexes were tested in asymmetric rhodium catalyzed hydrogenation of methyl 2-(acetamido)acrylate.

Novel supported substituted prolinamide as recyclable catalyst for asymmetric aldol reaction

2010

Stereoselective synthesis of carane-based chiral β- and γ-amino acid derivatives via conjugate addition

2015

Abstract Michael addition of dibenzylamine to (−)-tert-butyl isochaminate, prepared in three steps from (−)-perillaldehyde, furnished a carane-based β-amino acid derivative in a highly stereospecific reaction. The resulting amino ester was transformed to the bicyclic amino acid, a promising building block for the synthesis of 1,3-heterocycles and peptidomimetics. The conjugate addition of nitromethane to α,β-unsaturated methyl ester likewise resulted in nitro esters in stereospecific reactions. Catalytic reduction of the nitro group yielded a γ-amino ester. Under acidic conditions, the hydrolysis of the methyl ester resulted in an unexpected aminolactone-type product through rearrangement o…