Search results for "Asymmetric Synthesis"

“Nonsolvent” Applications of Ionic Liquids in Organocatalysis

2012

This chapter is organized in three sections (see Figure 10.1 ): 2. Immobilization of ionic liquids and organocatalysts 2.1 Covalently attached “ ionic liquid ” moieties as supports 2.2 Covalently attached “ ionic liquid ” moieties as linkers 2.3 Covalently attached “ ionic liquid ” moieties as organocatalysts

Organocatalytic asymmetric addition of naphthols and electron-rich phenols to isatin-derived ketimines: highly enantioselective construction of tetra…

2015

A quinine-derived thiourea organocatalyst promoted the highly enantioselective addition of naphthols and activated phenols to ketimines derived from isatins. The reaction afforded chiral 3-amino-2-oxindoles with a quaternary stereocenter in high yields (up to 99%) with excellent enantioselectivity (up to 99% ee). To the best of our knowledge, this transformation is the first highly enantioselective addition of naphthols to ketimines

Base-Dependent Stereodivergent Intramolecular Aza-Michael Reaction: Asymmetric Synthesis of 1,3-Disubstituted Isoindolines

2013

The nucleophilic addition (A(N)) / intramolecular aza-Michael reaction (IMAMR) process on Ellman's tert-butylsulfinyl imines, bearing a Michael acceptor in the ortho position, is studied. This reaction affords 1,3-disubstituted isoindolines with a wide range of substituents in good yields and diastereoselectivities. Interestingly, careful choice of the base for the aza-Michael step allows either the cis or the trans diastereoisomers to be exclusively obtained. This stereodivergent cyclization has enabled the synthesis of C2-symmetric bisacetate-substituted isoindolines. In addition, bisacetate isoindolines bearing two well-differentiated ester moieties are also noteworthy because they may a…

Highly Enantioselective Kinetic Resolution of Michael Adducts through N-Heterocyclic Carbene Catalysis: An Efficient Asymmetric Route to Cyclohexenes

2018

Ahighly efficient strategy for the kinetic resolu-tion of Michael adductswas realized using achiral N-het-erocyclic carbene catalyst.The kinetic resolution providesanew convenientroute to single diastereomers of cyclo-hexenes and Michael adducts in good yields with highenantiomeric excesses (up to 99 % ee with aselectivityfactor of up to 458). This “two flies with one swat” con-cept allows the synthesis of these two synthetically valua-ble compound classes at the same time by asingle trans-formation. peerReviewed

Asymmetric Synthesis of Functionalized Tricyclic Chromanes via an Organocatalytic Triple Domino Reaction

2017

A highly stereoselective triple domino reaction for the synthesis of functionalized tricyclic chromane scaffolds has been developed. A secondary amine-catalyzed domino Michael/Michael/aldol condensation reaction between aliphatic aldehydes, nitro-chromenes, and α,β-unsaturated aldehydes leads to the formation of synthetically important tricyclic chromanes bearing four contiguous stereogenic centers including a tetrasubstituted carbon in good yields (20–66%) and excellent stereoselectivities (>20:1 dr and >99% ee).

Asymmetric Synthesis of Spirocyclic β-Lactams through Copper-Catalyzed Kinugasa/Michael Domino Reactions

2018

The first copper-catalyzed highly chemo-, regio-, diastereo-, and enantioselective Kinugasa/Michael domino reaction for the desymmetrization of prochiral cyclohexadienones is described. In the presence of a chiral copper catalyst, alkyne-tethered cyclohexadienones couple with nitrones to generate the chiral spirocyclic lactams with excellent stereoselectivity (up to 97 % ee, >20:1 dr). The new method provides direct access to versatile highly functionalized spirocyclic β-lactams possessing four contiguous stereocenters, including one quaternary and one tetra-substituted stereocenter.

Organocatalytic Enantioselective Vinylogous Henry Reaction of 3,5-Dimethyl-4-nitroisoxazole with Trifluoromethyl Ketones

2017

The enantioselective vinylogous Henry reaction of 3,5-dimethyl-4-nitroisoxazole with trifluoromethyl ketones employing a bifunctional squaramide organocatalyst has been developed. A series of isoxazole bearing trifluoromethyl-substituted tertiary alcohols, 2-substituted (R)-1,1,1-trifluoro-3-(3-methyl-4-nitroisoxazol-5-yl)propan-2-ols, were obtained under these mild reaction conditions in good yields and moderate to good enantioselectivities

Asymmetric Synthesis of Spirocyclic β‐Lactams via Copper‐Catalyzed Kinugasa/Michael Domino Reactions

2018

The first copper‐catalyzed highly chemo‐, regio‐, diastereo‐, and enantioselective Kinugasa/Michael domino reaction for the desymmetrization of prochiral cyclohexadienones is described. In the presence of a chiral copper catalyst, alkyne‐tethered cyclohexadienones couple with nitrones to generate the chiral spirocyclic lactams with excellent stereoselectivity (up to 97 % ee, >20:1 dr). The new method provides direct access to versatile highly functionalized spirocyclic β‐lactams possessing four contiguous stereocenters, including one quaternary and one tetra‐substituted stereocenter. peerReviewed

N‐Heterocyclic Carbene Catalyzed Asymmetric Synthesis of Pentacyclic Spirooxindoles via [3+3] Annulations of Isatin‐Derived Enals and Cyclic N‐Sulfon…

2019

Enantiodivergent synthesis of P-chirogenic phosphines

2010

International audience; Several approaches for the enantiodivergent synthesis of P-chirogenic mono- and diphosphines are described, using ephedrine methodology and phosphine borane chemistry. Firstly, both enantiomers of a tertiary phosphine can be obtained starting from the same oxazaphospholidine borane complex, prepared from (+)-ephedrine, when changing the order of addition of the organolithium reagents during the synthetic pathway. The second approach is based on the chlorophosphine boranes, which react with an organolithium reagent, to afford the corresponding phosphines with inversion of configuration. In the case where the chlorophosphine borane reacts with the t-butyl lithium reage…