110611-21-7Relevant articles and documents
New C2-symmetric 2,4-bis(1-hydroxycyclopentyl)azetidines derived from (S)-1-phenylethylamine and their application in the enantioselective catalysis
Wilken, Joerg,Erny, Silke,Wassmann, Suzanne,Martens, Juergen
, p. 2143 - 2148 (2000)
The synthesis of new tridental 2,4-bis(1-hydroxycyclopentyl)azetidines using (S)-1-phenylethylamine as starting material is described. These new structures have been successfully applied in the enantiocontrolled catalytic addition of diethylzinc to aromatic aldehydes reaching enantiomeric excesses of up to 85% for the resulting 1-arylpropan-1-ols. Attempts in the field of the enantioselective oxazaborolidine-catalyzed reduction of ketones employing azetidine alcohols as precatalysts are also included. Copyright (C) 2000 Elsevier Science Ltd.
Reactions of aldehydes with diethylzinc catalysed by polymer-supported ephedrine and camphor derivatives: Comparisons of enantiomeric excesses achieved with various supports: Optimisation of support parameters to enable high enantiomeric excesses to be obtained
Sung, David W. L.,Hodge, Philip,Stratford, Peter W.
, p. 1463 - 1472 (1999)
The reactions of benzaldehyde with diethylzinc catalysed by PS ephedrine or camphor derivatives have been investigated in some depth in order to identify the crucial factors necessary to successfully prepare PS chiral catalysts for such reactions. The most important factor is found to be a favourable interaction of the polymer matrix with the reaction solvent so that the polymer will dissolve or swell to allow the other reactants easy access to the catalytic sites. Accordingly toluene is a better reaction solvent than hexane. The ephedrine-derived catalytic groups reduce the solubility of the linear polymers in toluene and, almost certainly, the swelling properties of the crosslinked polymers. Thus, of the polymers investigated the better linear ones had ca. 1.5 mmol per g of catalyst sites and the better insoluble ones were 1% crosslinked gels with ca. 1.0 mmol per g of catalyst sites. Site-site interactions and microenvironmental effects do not appear to play a major role in these PS reaction systems. For the reaction of benzaldehyde with diethylzinc, using the best linear PS ephedrine derivatives 10f, 10g or 11e affords 1-phenylpropanol (1) with 83-88% enantiomeric excesses (ee)s of the (R)-enantiomer; using the best linear PS camphor derivative 21 affords the alcohol 1 with a 98% ee of the (S)-enantiomer; using the best crosslinked PS ephedrine derivative 12a affords the alcohol 1 with a 78-81% ee and using the best crosslinked PS camphor derivative 22 affords alcohol 1 with a 97% ee of the (S)-enantiomer. These values are close to those obtained using analogues of non-polymeric catalysts under similar reaction conditions.
Enantioselective addition of Et2Zn to aldehydes promoted by a chiral schiff base metal complex
Cozzi, Pier Giorgio,Papa, Angelo,Umani-Ronchi, Achille
, p. 4613 - 4616 (1996)
An optically active zinc complex prepared with ligand 1 has been used to promote the enantioselective addition of Et2Zn to aldehydes. This study represents a new application for these metallo-salen complexes.
Heterogeneous asymmetric addition of diethylzinc to aromatic aldehydes catalyzed by Ti(IV)/imine bridged poly(R)-binaphthol
Dong, Chune,Zhang, Junlong,Zheng, Weizhong,Zhang, Liangfu,Yu, Zuolong,Choi, Michael C.K.,Chan, Albert S.C.
, p. 2449 - 2454 (2000)
Heterogeneous asymmetric addition of diethylzinc to aldehydes catalyzed by chiral polymer catalysts has been achieved. The conjugated polymers based on a BINOL skeleton were synthesized in five steps and applied to this reaction with yield and e.e. up to
Planar-Chiral Heterocycles as Ligands in Metal-Catalyzed Processes: Enantioselective Addition of Organozinc Reagents to Aldehydes
Dosa, Peter I.,Ruble, J. Craig,Fu, Gregory C.
, p. 444 - 445 (1997)
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A convergent, homochiral bis(amino alcohol) for obtaining high enantioselectivity in the addition of diethylzinc to aldehydes
Ooi, Takashi,Saito, Akira,Maruoka, Keiji
, p. 1108 - 1109 (2001)
A new bimetallic approach using dibenzofuran derivative as a requisite spacer has been introduced to achieve high asymmetric induction in the addition of diethylzinc to aldehydes with otherwise ineffective amino alcohol residue.
Enantioselective alkylation of aldehydes with diethylzinc catalyzed by C2-symmetric ligands
Williams, David R.,Fromhold, Mark G.
, p. 523 - 524 (1997)
The C2-symmetric pyridine 1, incorporating two units of (-)-ephedrine, is an effective catalyst for the enantioselective reactions of diethylzinc with a series of aromatic aldehydes. The propanol products possess the S-configuration. This resul
New applications of bis(oxazoline) ligands in catalysis: Asymmetric 1,2-and 1,4-addition of ZnR2 to carbonyl compounds
Schinnerl, Marina,Seitz, Michael,Kaiser, Anja,Reiser, Oliver
, p. 4259 - 4262 (2001)
(Matrix Presented) The enantioselective addition of ZnR2 to aldehydes (1,2) and cyclic enones (1,4) was accomplished using bis(oxazolines) as chiral ligands. The requirement for hydroxymethylene side chains in the ligands strongly suggests that bimetallic catalysts are decisive for high enantiocontrol in these additions.
Polymer-Bound Ephedrine as an Efficient Chiral Catalyst for the Enantioselective Addition of Dialkylzincs to Aldehydes
Soai, Kenso,Niwa, Seiji,Watanabe, Masami
, p. 927 - 928 (1988)
Polymer-bound ephedrine catalyzed the enantioselective addition of dialkylzincs to aldehydes.Optically active secondary alcohols in up to89percent ee were obtained.
2,2′-Bipyridine-α,α′-trifluoromethyl-diol ligand: Synthesis and application in the asymmetric Et2Zn alkylation of aldehydes
Lauzon, Samuel,Ollevier, Thierry
supporting information, p. 11025 - 11028 (2021/11/03)
A chiral 2,2′-bipyridine ligand (1) bearing α,α′-trifluoromethyl-alcohols at 6,6′-positions was designed in five steps affording either the R,R or S,S enantiomer with excellent stereoselectivities, i.e. 97% de, >99% ee and >99.5% de, >99.5% ee, respectively. The key step for reaching high levels of stereoselectivity was demonstrated to be the resolution of the α-CF3-alcohol using (S)-ibuprofen as the resolving agent. An initial application for the 2,2′-bipyridine-α,α′-CF3-diol ligand was highlighted in the ZnII-catalyzed asymmetric ethylation reaction of aromatic, heteroaromatic, and aliphatic aldehydes. Synergistic electron deficiency and steric hindrance properties of the newly developed ligand afforded the corresponding alcohols in good to excellent yields (up to 99%) and enantioselectivities (up to 95% ee). As observed from single crystal diffraction analysis, the complexation of the 2,2′-bipyridine-α,α′-CF3-diol ligand generates an unusual hexacoordinated ZnII.
Enantioselective Addition of Diethylzinc to Aromatic Aldehydes Using Novel Thiophene-Based Chiral Ligands
Aydin, A. E.
, p. 901 - 909 (2020/07/03)
Abstract: Chiral norephedrine-derived β-amino alcohols with a thiophene moiety were synthesized from thiophene carbaldehydes (methyl- or ethyl-substituted) and chiral amino alcohols, such as both enantiomers of norephedrine and 2-aminopropanol. The synthesized ligands were applied to the catalytic asymmetric addition of diethylzinc to aldehydes to obtain optically active alcohols with a high conversion (92%) and excellent enantioselectivities (ee up to 99%). The highest enantioselectivity (ee 99%) was obtained with p-trifluorobenzaldehyde as the substrate containing the strongly electron-acceptor CF3 group.
Towards practical earth abundant reduction catalysis: Design of improved catalysts for manganese catalysed hydrogenation
Widegren, Magnus B.,Clarke, Matthew L.
, p. 6047 - 6058 (2019/11/14)
Manganese catalysts derived from tridentate P,N,N ligands can be activated easily using weak bases for both ketone and ester hydrogenations. Kinetic studies indicate the ketone hydrogenations are 0th order in acetophenone, positive order in hydrogen and 1st order in the catalyst. This implies that the rate determining step of the reaction was the activation of hydrogen. New ligand systems with varying donor strength were studied and it was possible to make the hydrogen activation significantly more efficient; a catalyst displaying around a 3-fold increase in initial turn-over frequencies for the hydrogenation of acetophenone relative to the parent system was discovered as a result of these kinetic investigations. Ester hydrogenations and ketone transfer hydrogenation (isopropanol as reductant) are first order for both the substrate and catalysts. Kinetic studies also gained insight into catalyst stability and identified a working range in which the catalyst is stable throughout the catalytic reaction (and a larger working range where high yields can still be achieved). The new more active catalyst, combining an electron-rich phosphine with an electron-rich pyridine is capable of hydrogenating acetophenone using as little as 0.01 mol% catalyst at 65 °C. In all, protocols for reduction of 21 ketones and 15 esters are described.
