22461-89-8Relevant articles and documents
In search of new approaches to asymmetric conjugate addition: Screening studies on the use of [Zn(bpy*)X(R)] reagents and α,β- unsaturated amide Michael acceptors
Blake, Alexander J.,Giunta, Daniela,Jonathanss-SHANNON,Solinas, Maurizio,Walzer, Francesca,Woodward, Simon
, p. 1107 - 1121 (2007)
Conjugate additions of [Zn(bpy*)Cl(Et)] (bpy* = 4,4′-di-tert-butyl-2,2′-bipyridine) to cyclohex-2-en-1-one are promoted by ZnMe2 in 88% ee but in moderate yield under Cu I phosphoramidite catalysis. In the absence of ZnMe2 the [Zn(bpy*)Cl(Et)] is inactive indicating a Schlenk-type equilibrium. Other derivatives of [Zn(bpy*)Cl(R)] (R = Bu, 4-methylbenzyl), prepared in situ from [ZnCl(R)] and the bipyridine give low yields due to competing chloride abstraction. 13C NMR studies indicate facile organo-ligand exchange between [Zn(bpy*)(Et)2] and [Zn(bpy*)Cl2] complexes. In the presence of the bipyridine, [ZnBr(allyl)] disproportionates into [Zn(bpy*)Br2] and [Zn(bpy*)(allyl)2] species. In separate studies, simple (E)-MeCH=CHCONMeR (R = Me, OMe) α,β-unsaturated amides undergo asymmetric 1,4-addition of EtMgBr in 75-99% yield and 48-79% ee in the presence of the diphosphines JosiPhos or MeDuPhos and copper(I) sources.
Evaluation of a chiral cubane-based Schiff base ligand in asymmetric catalysis reactions
Biegasiewicz, Kyle F.,Ingalsbe, Michelle L.,Priefer, Ronny,St. Denis, Jeffrey D.,Gleason, James L.,Ho, Junming,Coote, Michelle L.,Savage, G. Paul
, p. 1814 - 1818,5 (2012)
Recently, a novel chiral cubane-based Schiff base ligand was reported to yield modest enantioselectivity in the Henry reaction. To further explore the utility of this ligand in other asymmetric organic transformations, we evaluated its stereoselectivity i
1,4-Addition of diethylzinc to cyclohexenone catalyzed by CuOTf-sulfonamide combined system. Evidence supporting a concerted mechanism
Nakano, Keiji,Bessho, Yuhki,Kitamura, Masato
, p. 224 - 225 (2003)
Measurement of 12C/13C isotope effect in the Cu(I)/sulfonamide-catalyzed 1,4-addition of diethylzinc to 2-cyclohexenone implies that the reaction proceeds by a concerted mechanism, different to those so far reported for the conventio
Observation of Ethyl-Substituted Cyclohexanone and Cyclopentanone Rotamers Using Resonance-Enhanced Multiphoton Ionization Spectroscopy
Nesselrodt, Dale R.,Potts, Alan R.,Baer, Tomas
, p. 4458 - 4465 (1995)
The various rotamer conformations associated with the hindered ethyl group rotor in ethyl-substituted cyclohexanones and cyclopentanones have been trapped in a supersonic expansion and spectroscopically analyzed by 2 + 1 resonance-enhanced multiphoton ionization via the 3s - n Rydberg transition.The rapid cooling in the supersonic expansion effectively freezes many of the conformations at their room temperature equilibrium concentrations.The various rotamers, including some in the axial orientation, were identified by comparing peak intensities with those calculated by both molecular mechanics and ab initio MO methods.Excellent agreement between the calculations and the experimental results is noted.
Preparation of silane-grafted pellets: Silica bound reagents in a very convenient form
Timofte, Roxana S.,Woodward, Simon
, p. 39 - 42 (2004)
High surface area silica pellets are excellent supports for the preparation of silica supported reagents and solid-phase basal linkers through reaction with (RO)3Si(CH2)3FG (FG=NH 2, NHMe, Cl, NHC(=O)NH2/s
A modular approach to a new class of monodentate chiral phosphorus ligands and their application in enantioselective copper-catalysed conjugate additions of diethylzinc to cyclohexenone
Monti, Chiara,Gennari, Cesare,Steele, Rebecca M.,Piarulli, Umberto
, p. 3557 - 3565 (2004)
A new family of chiral phosphorus ligands (5) for use in enantioselective catalysis have been synthesised. The ligands contain the electron-poor bis(sulfonyl)diazaphospholidine moiety and possess a highly modular structure which is well suited to the synthesis of a library. A small library (23 members) of ligands 5 was prepared and tested in the enantioselective copper-catalysed conjugate addition of diethylzinc to cyclohexenone. Complete conversions were obtained with enantiomeric excesses (ee) of up to 75%. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.
Diethylzinc: A chain-transfer agent in intermolecular radical additions. A parallel with triethylborane
Bertrand, Michele P.,Feray, Laurence,Nouguier, Robert,Perfetti
, p. 9189 - 9193 (1999)
In the presence of oxygen, diethylzinc can be used to promote radical additions to C=N bond containing radical acceptors and to enones. In these reactions, it plays at the same time the role of the initiator and the role of the chain-transfer reagent. A p
Thioether-phosphinite and diphosphinite ligands derived from D-xylose for the copper-catalyzed asymmetric 1,4-addition to 2-cyclohexenone
Guimet, Eugeni,Dieguez, Montserrat,Ruiz, Aurora,Claver, Carmen
, p. 2161 - 2165 (2005)
A series of thioether-phosphinite 1-3 and diphosphinite 4 and 5 ligands, derived from inexpensive D-(+)-xylose, were tested for the first time in the Cu-catalyzed asymmetric 1,4-addition to 2-cyclohexenone 6. Good enantioselectivities (up to 72%) and acti
New phosphoramidite and phosphito-N chiral ligands based on 8-substituted quinolines and (S)-binaphthol; applications in the Cu-catalyzed enantioselective conjugate addition of diethylzinc to 2-cyclohexen-1-one
Arena, Carmela G.,Calabro, Gianpiero,Francio, Giancarlo,Faraone, Felice
, p. 2387 - 2392 (2000)
The copper(II)-catalyzed enantioselective conjugate addition of diethylzinc to 2-cyclohexen-1-one, in the presence of phosphoramidite and of phosphito-N chiral ligands, derived from 8-chloroquinoline or 8-hydroxyquinoline and (S)-4-chloro-3,5-dioxa-4-phos
Copper-catalysed asymmetric 1,4-addition of organometallic reagents to 2-cyclohexenone using novel phosphine-phosphite ligands
Dieguez, Montserrat,Deerenberg, Sirik,Pamies, Oscar,Claver, Carmen,Van Leeuwen,Kamer, Paul
, p. 3161 - 3166 (2000)
A series of novel non-symmetrical phosphine-phosphite ligands 1-10 have been tested in the copper-catalysed asymmetric addition of diethylzinc and triethylaluminium to 2-cyclohexenone. In all cases, excellent conversion and regioselectivities for the 1,4-product were found. Good enantiomeric excesses (up to 62%) were obtained when triethylaluminium was used as the alkylating reagent. Copyright (C) 2000 Elsevier Science Ltd.
