Synthesis of enantiopure amino alcohols by ring-opening of epoxyalcohols and epoxyethers with ammonia
摘要:
Arylglycidols and their corresponding ethers undergo regioselective ring-opening with aqueous ammonia in the presence of organic co-solvents (isopropanol or 1,4-dioxane) to afford 1,2-amino alcohols in high yield. (C) 2003 Elsevier Ltd. All rights reserved.
Phosphinooxazolines Derived from 3-Amino-1,2-diols: Highly Efficient ModularP-N Ligands
作者:Dana Popa、Cristina Puigjaner、Montserrat Gómez、Jordi Benet-Buchholz、Anton Vidal-Ferran、Miquel A. Pericàs
DOI:10.1002/adsc.200600599
日期:2007.10.8
palladium complexes have been used as chiral mediators in the asymmetric allylic alkylation reaction. The oxazoline moiety in 12 contains a C-4 aryl and a C-5 alkoxymethyl substituent that can be independently optimized for high catalytic activity and enantioselectivity. A methoxymethyl substituent at C-5 has been found to provide the best results in terms of enantioselectivity and activity in the alkylation
stereodefined, modular aminoalcohols (3-alkoxy-1-amino-1-phenyl-2-propanols), in which the steric bulk of the alkoxy and amino substituents varies smoothly, has been synthesized from enantiomerically pure phenylglycidol, prepared by Sharpless epoxidation. These aminoalcohols have been evaluated as ligands in the catalyzed [(aminoalcohol)(arene)RuII] transfer hydrogenation of alkyl aryl ketones,
5-cis (6 c) stereochemistry at the individual rings have been prepared in high yield. Their eta(3)-allyl palladium complexes (8 a-g, 9 c and 10) have been used as catalytic precursors in allylic alkylation reactions with excellent enantioselectivities (up to 96 %) for the trans oxazoline derivatives, while Pd/6 c system was inactive. NMR studies on palladium eta(3)-1,3-diphenylallyl intermediates (11
Highly enantioselective dynamic kinetic resolution and desymmetrization processes by cyclocondensation of chiral aminoalcohols with racemic or prochiral δ-oxoacid derivatives
作者:Mercedes Amat、Oriol Bassas、Miquel A. Pericàs、Mireia Pastó、Joan Bosch
DOI:10.1039/b413937b
日期:——
Cyclocondensation reactions of aminoalcohols and with racemic or prochiral delta-oxoacid derivatives provide polysubstituted lactams with high enantioselectivity in a process that involves dynamic kinetic resolution and/or desymmetrization of enantiotopic or diastereotopic ester groups.
A New Family of Modular Chiral Ligands for the Catalytic Enantioselective Reduction of Prochiral Ketones
作者:Cristina Puigjaner、Anton Vidal-Ferran、Albert Moyano、Miquel A. Pericàs、Antoni Riera
DOI:10.1021/jo990942q
日期:1999.10.1
A family of enantiomerically pure (4R,5R)-2-alkyl-4-phenyl-5-(R-oxymethyl) 1,3,2-oxazaborolidines (5) [boron substituent: H, CH3, n-C4H9; R-oxy group: CH3O, CH3OCH2CH2O, CH3(OCH2CH2)(2)O, PhCH2O, Ph2CHO, Ph3CO] has been prepared from (2S,3S)-2,3-epoxy-3-phenylpropanol (2) through a four-step sequence involving protection of the alcohol, regioselective ring-opening of the epoxide with sodium azide in acetonitrile in the presence of LiClO4, reduction of the azido group (H-2/PdC/MeOH or NaBH4/THF-MeOH), and formation of the oxazaborolidine ring with the appropriate boron reagent. Both the boron substituent and the R-oxy group have been optimized for maximal enantioselectivity in the reduction of prochiral ketones with borane. The optimal oxazaborolidine (5a-Me) [boron substituent: CH3; R-oxy group: CH3O] has been employed (10% molar amount, THF, 0 degrees C to room temperature) in the reduction of a representative family of 10 substrates comprising alkyl aryl ketones and dialkyl ketones. In these reductions, Ba-Rie induces the formation of secondary alcohols of S configuration with high enantioselectivity (93% mean enantiomeric excess). The origin of the enantioselectivity in the reduction has been rationalized by means of semiempirical AM1 calculations.