72746-41-9Relevant academic research and scientific papers
Counterion Enhanced Organocatalysis: A Novel Approach for the Asymmetric Transfer Hydrogenation of Enones
Scharinger, Fabian,Márk Pálv?lgyi, ádám,Zeindlhofer, Veronika,Schnürch, Michael,Schr?der, Christian,Bica-Schr?der, Katharina
, p. 3776 - 3782 (2020/06/22)
We present a novel strategy for organocatalytic transfer hydrogenations relying on an ion-paired catalyst of natural l-amino acids as main source of chirality in combination with racemic, atropisomeric phosphoric acids as counteranion. The combination of a chiral cation with a structurally flexible anion resulted in a novel chiral framework for asymmetric transfer hydrogenations with enhanced selectivity through synergistic effects. The optimized catalytic system, in combination with a Hantzsch ester as hydrogen source for biomimetic transfer hydrogenation, enabled high enantioselectivity and excellent yields for a series of α,β-unsaturated cyclohexenones under mild conditions. Moreover, owing to the use of readily available and chiral pool-derived building blocks, it could be prepared in a straightforward and significantly cheaper way compared to the current state of the art.
CuI-Catalysed Enantioselective Alkyl 1,4-Additions to (E)-Nitroalkenes and Cyclic Enones with Phosphino-Oxazoline Ligands
Shin, Minkyeong,Gu, Minji,Lim, Sung Soo,Kim, Min-Jae,Lee, JuHyung,Jin, HyeongGyu,Jang, Yun Hee,Jung, Byunghyuck
, p. 3122 - 3130 (2018/07/06)
Catalytic enantioselective conjugate additions of simple alkyl groups to nitroalkenes or cyclic enones that result in the formation of tertiary C–C bonds are described. For these stereoselective addition reactions, new chiral phosphino-oxazoline ligands w
A convenient catalytic asymmetric conjugate addition reaction to enones using alkylzirconium reagents
Maksymowicz, Rebecca M.,Sidera, Mireia,Roth, Philippe M. C.,Fletcher, Stephen P.
supporting information, p. 2662 - 2668 (2013/10/21)
Alkylzirconium reagents undergo highly enantioselective copper-catalysed 1,4-addition reaction to cyclic enones. These reactions use alkylmetal species generated in situ from alkenes and the Schwartz reagent, and do not require premade organometallic reag
Chiral hetero- and carbocyclic compounds from the asymmetric hydrogenation of cyclic alkenes
Verendel, J. Johan,Li, Jia-Qi,Quan, Xu,Peters, Byron,Zhou, Taigang,Gautun, Odd R.,Govender, Thavendran,Andersson, Pher G.
supporting information; experimental part, p. 6507 - 6513 (2012/06/29)
Several types of chiral hetero- and carbocyclic compounds have been synthesized by using the asymmetric hydrogenation of cyclic alkenes. N,P-Ligated iridium catalysts reduced six-membered cyclic alkenes with various substituents and heterofunctionality in good to excellent enantioselectivity, whereas the reduction of five-membered cyclic alkenes was generally less selective, giving modest enantiomeric excesses. The stereoselectivity of the hydrogenation depended more strongly on the substrate structure for the five- rather than the six-membered cyclic alkenes. The major enantiomer formed in the reduction of six-membered alkenes could be predicted from a selectivity model and isomeric alkenes had complementary enantioselectivity, giving opposite optical isomers upon hydrogenation. The utility of the reaction was demonstrated by using it as a key step in the preparation of chiral 1,3-cis-cyclohexane carboxylates. Copyright
Hydroxy-amide functionalized azolium salts for Cu-catalyzed asymmetric conjugate addition: Stereocontrol based on ligand structure and copper precatalyst
Shibata, Naoatsu,Yoshimura, Misato,Yamada, Haruka,Arakawa, Ryuichi,Sakaguchi, Satoshi
experimental part, p. 4079 - 4086 (2012/06/04)
A series of hydroxy-amide functionalized azolium salts have been designed and synthesized for Cu-catalyzed asymmetric conjugate addition reaction. The (CH2)2-bridged hydroxy-amide functionalized azolium ligand precursors 2, in addition to the previously reported CH2-bridged azolium salts 1, have been prepared from readily available enantiopure β-amino alcohols. The combination of a Cu species with 1 or 2 efficiently promoted the 1,4-addition reaction of cyclic enones with dialkylzincs. For example, the reaction of 2-cyclohepten-1-one (17) with Bu2Zn in the presence of catalytic amounts of Cu(OTf)2 and 1 gave (S)-3-butylcycloheptanone (20) in 99% yield and 96% ee. On the other hand, when the reaction was carried out under the influence of Cu(OTf)2 combined with 2, (R)-20 in preference to (S)-20 was obtained in 98% yield and 80% ee. In this manner, the enantioselecvity was switched by controlling the structure of chiral ligand. Additionally, the reversal of enantioselectivity was also achieved by changing the Cu precatalyst from Cu(OTf)2 to Cu(acac)2 with the same ligand. The combination of Cu(acac) 2 with CH2-bridged azolium salt 1 in the reaction of 17 with Bu2Zn led to formation of (R)-20 as a major product in 55% yield and 80% ee. This result was in contrast to the Cu(OTf)2/1 catalytic system, where the 1,4-adduct with opposite configuration was obtained. Moreover, use of the Cu(acac)2/2 catalytic system produced (S)-20, while (R)-20 was formed by the Cu(OTf)2/2 catalytic system. Thus, it was found that either varying the linker of the chiral ligands or changing the counterion of Cu species between a OTf and acac ligand initially on the metal led to dual enantioselective control in the 1,4-addition reaction.
Ligand design for dual enantioselective control in Cu-catalyzed asymmetric conjugate addition of R2Zn to cyclic enone
Yoshimura, Misato,Shibata, Naoatsu,Kawakami, Miaki,Sakaguchi, Satoshi
experimental part, p. 3512 - 3518 (2012/06/04)
A new chiral N-heterocyclic carbene (NHC) ligand derived from a natural α-aminoester has been designed and synthesized. The coupling of N-methylbenzimidazole with an α-chloroacetamide derivative, which was prepared from chloroacetyl chloride and (S)-serin
Catalytic enantioselective conjugate addition of Grignard reagents to cyclic enones using C1-1,1′-bisisoquinoline-based chiral ligands
Qi, Gao,Judeh, Zaher M.A.
experimental part, p. 1585 - 1592 (2012/05/04)
New highly constrained chiral C1-1,1′-bisisoquinoline ligands were examined in the enantioselective conjugate addition of Grignard reagents to cyclohexenone and cyclopentenone. The desired 1,4-adducts were obtained in excellent yield and moderate enantiomeric excess (up to 35%). Copyright Taylor & Francis Group, LLC.
Preparation and characterization of new C2- and C 1-symmetric nitrogen, oxygen, phosphorous, and sulfur derivatives and analogs of TADDOL. part i
Pichota, Arkadius,Gramlich, Volker,Beck, Albert K.,Seebach, Dieter
experimental part, p. 1239 - 1272 (2012/09/21)
The chloro alcohols 4-6 derived from TADDOLs (=α,α, α′,α′-tetraaryl-1,3-dioxolan-4,5-dimethanols) are used to prepare corresponding sulfanyl alcohols, ethers, and amines (Scheme 1 and Table 1). The dithiol analog of TADDOL and derivatives thereof, 45-49,
A new C2-symmetric azolium compound for Cu-catalyzed asymmetric conjugate addition of R2Zn to cyclic enone
Harano, Ayako,Sakaguchi, Satoshi
experimental part, p. 61 - 67 (2011/02/16)
A new chiral N-heterocyclic carbene (NHC) ligand was designed. Thus, an efficient synthetic route to C2-symmetric bis(hydroxyamide)- functionalized benzimidazolium salts from chiral β-amino alcohols was developed. The combination of Cu(OTf)sub
Enantioselective copper-catalyzed 1,4-addition of dialkylzincs to enones followed by trapping with allyl iodide derivatives
Kawamura, Kenjiro,Fukuzawa, Hitomi,Hayashi, Masahiko
experimental part, p. 640 - 647 (2011/08/06)
Enantioselective copper-catalyzed 1,4-addition of dialkylzincs to enones proceeded in the presence of 0.1 mol% of Cu(OTf)2 and 0.25 mol% of an N,N,P-ligand containing a quinoline moiety to afford the corresponding conjugated adducts in 99%ee. The intermediate zinc enolates were trapped with substituted allyl iodides to give disubstituted ketones with high diastereoselectivity and enantioselectivity.
