Search results for "selective synthesis"
showing 10 items of 430 documents
ChemInform Abstract: Highly Enantioselective Copper(I)-Catalyzed Conjugate Addition of 1,3-Diynes to α,β-Unsaturated Trifluoromethyl Ketones.
2015
The conjugate diynylation of α,β-saturated trifluoromethyl ketones is carried out at low catalytic loading (2.5 mol% for aryl substituents) of a copper(I)—MeO-BIPHEP complex, triethylamine and a terminal 1,3-diyne.
ChemInform Abstract: Enantioselective Allylic Substitution Using a Novel (Phosphino-α-D-glucopyrano-oxazoline)palladium Catalyst.
2010
A Highly Enantioselective Access to Tetrahydroisoquinoline and β-Carboline Alkaloids with Simple Noyori-Type Catalysts in Aqueous Media
2009
ChemInform Abstract: Organocatalytic Enantioselective Synthesis of Pyrazoles Bearing a Quaternary Stereocenter.
2016
An efficient one-pot asymmetric synthesis of pyrazoles bearing a chiral quaternary stereocenter has been developed. Quinine-derived thiourea catalyzed the enantioselective addition of pyrazolones to isatin-derived ketimines, providing the corresponding acetylated pyrazoles after in situ treatment with Ac2 O/Et3 N. The corresponding pyrazoles were afforded in high yields and excellent enantioselectivities.
ChemInform Abstract: Dual Hydrogen-Bond/Enamine Catalysis Enables a Direct Enantioselective Three-Component Domino Reaction.
2011
A dual system, composed of an enantioselective enamine catalyst and a multiple-hydrogen-bond catalyst achieves the three-component enantioselective aldehyde—nitroalkene—aldehyde domino reaction using either two similar or two different aldehydes.
A Simple Organocatalytic Enantioselective Synthesis of Pregabalin
2009
This paper describes a new procedure for the enantioselective synthesis of the important anticonvulsant drug Pregabalin, which shows biological properties as the (S) enantiomer only. The key step of the synthetic sequence is the Michael addition reaction of Meldrum's acid to a nitroalkene mediated by a quinidine derived thiourea. A variety of novel catalysts bearing different groups at the thiourea moiety were synthesized and tested. The most successful catalyst that incorporates a trityl substituent provided up to 75 % ee of (S)-4. The conjugate addition reaction was carried out on a multigram scale with low loadings of catalyst (10 mol-%). Moreover, the catalyst can be recycled showing th…
Frontispiece: Recent Advances in Enantioselective Desymmetrizations of Prochiral Oxetanes
2021
Cyclic Sulfonimidates by Dynamic Diastereomer-Differentiating Cyclisation: Large-Scale Synthesis and Mechanistic Studies
2001
A dynamic diastereomer differentiating cyclisation is the key step in a new large-scale synthesis of both enantiomers of the cyclic sulfonimidates 1 (Aldrich no. 54099-4) and ent-1 (Aldrich no. 54412-4). These are valuable starting materials in the asymmetric synthesis of chiral oxa- and azaheterocyclic compounds. NMR spectroscopic studies on the reacting system reveal N-chloro sulfinamides to be reactive intermediates in the oxidative chlorination of sulfinamides with tert-butyl hypochlorite and allow for the inspection of the configurational behaviour of the involved sulfonimidoyl chlorides and sulfonimidoyl bromides.
ChemInform Abstract: Organocatalytic Enantioselective Alkylation of Pyrazol-3-ones with Isatin-Derived Ketimines: Stereocontrolled Construction of Vi…
2016
Financial support from the MINECO (Gobierno de Espana and FEDER (EU)) (CTQ2013-47949-P) and from Generalitat Valenciana (ISIC2012/001) is gratefully acknowledged. C. V. thanks MINECO for JdC contract. Access to NMR, MS and X-ray facilities from the Servei central de support a la investigacio experimental (SCSIE)-UV is also acknowledged.
Enantioselective organocatalytic intramolecular aza-Michael reaction: a concise synthesis of (+)-sedamine., (+)-allosedamine, and (+)-coniine
2007
The intramolecular aza-Michael reaction of carbamates bearing remote alpha,beta-unsaturated aldehydes under organocatalytic conditions took place with good yields and excellent ee's when Jorgensen catalyst IV was used in the process, giving rise to the enantioselective formation of several five- and six-membered heterocycles. The developed methodology was applied to the synthesis of three piperidine alkaloids.