850494-79-0Relevant articles and documents
Alternatives to Phosphinooxazoline (t-BuPHOX) Ligands in the Metal-Catalyzed Hydrogenation of Minimally Functionalized Olefins and Cyclic β-Enamides
Biosca, Maria,Magre, Marc,Coll, Mercè,Pàmies, Oscar,Diéguez, Montserrat
, p. 2801 - 2814 (2017)
This study presents a new series of readily accessible iridium- and rhodium-phosphite/oxazoline catalytic systems that can efficiently hydrogenate, for the first time, both minimally functionalized olefins and functionalized olefins (62 examples in total) in high enantioselectivities (ees up to >99%) and conversions. The phosphite-oxazoline ligands, which are readily available in only two synthetic steps, are derived from previous privileged 4-alkyl-2-[2-(diphenylphosphino)phenyl]-2-oxazoline (PHOX) ligands by replacing the phosphine moiety by a biaryl phosphite group and/or the introduction of a methylene spacer between the oxazoline and the phenyl ring. The modular design of the ligands has given us the opportunity not only to overcome the limitations of the iridium-PHOX catalytic systems in the hydrogenation of minimally functionalized Z-olefins and 1,1-disubstituted olefins, but also to expand their use to unfunctionalized olefins containing other challenging scaffolds (e.g., exocyclic benzofused and triaryl-substituted olefins) and also to olefins with poorly coordinative groups (e.g., α,β-unsaturated lactams, lactones, alkenylboronic esters, etc.) with enantioselectivities typically >95% ee. Moreover, both enantiomers of the hydrogenation product could be obtained by simply changing the configuration of the biaryl phosphite moiety. Remarkably, the new catalytic systems also provided excellent enantioselectivities (up to 99% ee) in the asymmetric hydrogenation of another challenging class of olefins – the functionalized cyclic β-enamides. Again, both enantiomers of the reduced amides could be obtained by changing the metal from Ir to Rh. We also demonstrated that environmentally friendly propylene carbonate can be used with no loss of enantioselectivity. Another advantage of the new ligands over the PHOX ligands is that the best ligands are derived from the affordable (S)-phenylglycinol rather than from the expensive (S)-tert-leucinol. (Figure presented.).
Chiral oxazoline ligands. Synthesis and characterization of palladium, nickel and manganese complexes containing bidentate N,O and N,P moieties
Gomez-Simon, Montserrat,Jansat, Susanna,Muller, Guillermo,Panyella, David,Font-Bardia, Merce,Solans, Xavier
, p. 3755 - 3764 (1997)
Complexes of palladium, nickel and manganese, with the chiral ligand (+)-(4′R)-2-(4′-ethyl-3′,4′-dihydrooxazol-2′-yl) phenol HLOH were synthesized and characterized by 1H, 31P NMR spectroscopy, magnetic susceptibility and including the crystal structure determinations of trans-[PdLOH2] and [PdClLOH(PPh3)]. The LOH moiety is co-ordinated in a bidentate fashion in neutral, cationic and anionic complexes, rigid on the NMR time-scale. Monodentate O-co-ordinated complexes were obtained only in the presence of phosphines. The manganese complex [MnClLOH2] showed little activity in the catalytic epoxidation of styrene. The first phosphinite oxazoline ligand LOP was synthesized from HLOH. Neutral and cationic alkyl and allyl complexes of palladium with it were obtained and characterized. The cationic complexes showed dynamic behaviour.
The Taiji and Eight Trigrams chemistry philosophy of chiral iridium(III) complexes with triplex stereogenic centers
Yan, Zhi-Ping,Luo, Xu-Feng,Liao, Kang,Lin, Zi-Xuan,Wu, Zheng-Guang,Zhou, Yong-Hui,Zheng, You-Xuan
supporting information, p. 4045 - 4048 (2018/03/26)
Four novel chiral iridium(iii) complexes with triplex stereogenic centers were synthesized by introducing chiral carbon atoms into cyclometalated and ancillary ligands, and separated into eight isomers, which coincide with the old Chinese philosophy Eight Trigrams. The electron circular dichroism and circularly polarized luminescence spectra of four pairs of isomers show perfect mirror images with a dissymmetry factor (glum factor) of around 0.003.
