Search results for "enantioselective synthesis"
showing 10 items of 418 documents
Natural eutectogels: sustainable catalytic systems for C–C bond formation reactions
2021
Natural eutecto gels were prepared combining properties of amino acids with the ones of deep eutectic solvents. Soft materials obtained were fully characterised determining the gel-sol transition temperatures and analysing mechanical and morphological features through rheological measurements and polarised optical microscopy. All eutecto gels were tested as catalytic reaction media for the enantioselective aldol reaction and, the best performing one was also used to carry out the Michael addition. In both cases, eutecto gels proved to have a great potential as sustainable reaction media, allowing to perform processes under mild conditions, obtaining excellent yields and, in some cases, also…
A Decade of Advance in the Asymmetric Vinylogous Mannich Reaction
2016
When the principle of vinylogy is applied to imines as electrophiles, the so-called vinylogous Mannich reaction (VMR), γ-aminocarbonyl (such as butenolides) and β-aminocarbonyl compounds are generated in a very efficient manner. The asymmetric version of this vinylogous Mannich reaction gives access to highly functionalized chiral synthons, which are suitable for further transformations. The versatility of this methodology is exemplified with the synthesis of several alkaloids and natural products. 1 Introduction 2 Asymmetric Vinylogous Mannich Reactions (VMR) with 2-Silyloxyfurans and 2-Silyloxypyrroles 3 Asymmetric VMR with Acyclic Silyl Dienolates and Silyl Dienol Ketene Acetals 4 Asymm…
Highly enantioselective aza-Henry reaction with isatin N-Boc ketimines.
2014
A highly enantioselective aza-Henry reaction with isatin N-Boc ketimines using a Cu(II)–BOX complex as a catalyst is described. The reaction, which does not require protection of the N1 atom, provides the corresponding nitroamines bearing a quaternary stereocentre with high yields and enantiomeric excesses (up to 99.9%).
Concise asymmetric synthesis of Linezolid through catalyzed Henry reaction
2013
A new asymmetric synthesis of the antibiotic Linezolid was performed through a copper-catalyzed Henry reaction as the key step. The use of camphor-derived aminopyridine ligands helped to improve the yields of the chiral precursor and to obtain Linezolid in good overall yield and enantiomeric excess.
A catalytic highly enantioselective direct synthesis of 2-bromo-2-nitroalkan-1-ols through a Henry reaction.
2008
Highly enantiomerically enriched 2-bromo-2-nitroalkan-1-ols are prepared by direct condensation of aliphatic and aromatic aldehydes with bromonitromethane in the presence of a catalytic amount of copper(II) acetate and a C1-symmetric camphorderived amino pyridine ligand. Blay Llinares, Gonzalo, Gonzalo.Blay@uv.es ; Hernandez Olmos, Victor, Victor.Hernandez@uv.es ; Pedro Llinares, Jose Ramon, Jose.R.Pedro@uv.es
Modular iminopyridine ligands. Application to the enantioselective copper(II)-catalyzed Henry reaction
2006
Abstract Chiral iminopyridines prepared in a modular fashion from monoterpenic (camphor-derived) ketones and pyridinylalkylamines catalyze the enantioselective Henry (nitro aldol) reaction between nitromethane and o -anisol in the presence of copper(II) acetate, with high yields and good ee (up to 86%) under straightforward experimental conditions without the need for air or moisture exclusion.
Enantioselective Henry reaction catalyzed with copper(II)–iminopyridine complexes
2007
Abstract Copper complexes of chiral iminopyridines prepared from camphane-derived ketones and picolylamine catalyzed the enantioselective Henry (nitroaldol) reaction between nitromethane and a number of aromatic and aliphatic aldehydes with high yields and good enantioselectivities. Iminopyridines derived from (1 R )-(+)-camphor and (1 S )-(+)-ketopinic acid gave the best results to afford the opposite enantiomers in each case, despite the fact they have the same stereochemical pattern at the camphane skeleton. The reactions were carried out without air or moisture exclusion.
New highly asymmetric Henry reaction catalyzed by Cu(II) and a C(1)-symmetric aminopyridine ligand, and its application to the synthesis of miconazol…
2008
A new catalytic asymmetric Henry reaction has been developed that uses a C(1)-symmetric chiral aminopyridine ligand derived from camphor and picolylamine. A variety of aromatic, heteroaromatic, aliphatic, and unsaturated aldehydes react with nitromethane and other nitroalkanes in the presence of DIPEA (1.0 equiv), Cu(OAc)(2)*H(2)O (5 mol %), and an aminopyridine ligand (5 mol %) to give the expected products in high yields (up to 99 %), moderate-to-good diastereoselectivites (up to 82:18), and excellent enantioselectivities (up to 98 %). The reaction is air-tolerant and has been used in the synthesis of the antifungal agent miconazole.
Enantioselective Addition of Nitromethane to 2-Acylpyridine N-Oxides. Expanding the Generation of Quaternary Stereocenters with the Henry Reaction
2014
[EN] The direct asymmetric Henry reaction with prochiral ketones, leading to tertiary nitroaldols, is an elusive reaction so far limited to a reduced number of reactive substrates such as trifluoromethyl ketones or alpha-keto carbonyl compounds. Expanding the scope of this important reaction, the direct asymmetric addition of nitromethane to 2-acylpyridine N-oxides catalyzed by a BOX-Cu(II) complex to give the corresponding pyridine-derived tertiary nitroaldols having a quaternary stereogenic center with variable yields and good enantioselectivity, is described.
ChemInform Abstract: Asymmetric Tandem Reactions: New Synthetic Strategies
2010
The use of domino and multicomponent reactions in asymmetric synthesis is con- stantly increasing nowadays. This allows for the synthesis of complex molecules in a single synthetic sequence, usually with high atom economy. Herein, we report three examples of new asymmetric tandem reactions recently developed in our laboratories, giving rise to new families of enantiomerically enriched fluorinated and nonfluorinated heterocycles. Thus, 1,4-dihydropyridines (1,4-DHPs) bearing fluorinated substituents at C6 were assembled by means of a Hantzsch-type reaction; cyclic β-amino carbonyl derivatives were prepared using a cross-metathesis (CM)-intramolecular aza-Michael sequence; while fluorinated i…