910443-08-2Relevant academic research and scientific papers
Highly efficient enantioselective liquid-liquid extraction of 1,2-amino-alcohols using SPINOL based phosphoric acid hosts
Pinxterhuis, Erik B.,Gualtierotti, Jean-Baptiste,Heeres, Hero J.,De Vries, Johannes G.,Feringa, Ben L.
, p. 6409 - 6418 (2017/08/29)
Access to enantiopure compounds on large scale in an environmentally friendly and cost-efficient manner remains one of the greatest challenges in chemistry. Resolution of racemates using enantioselective liquid-liquid extraction has great potential to meet that challenge. However, a relatively feeble understanding of the chemical principles and physical properties behind this technique has hampered the development of hosts possessing sufficient resolving power for their application to large scale processes. Herein we present, employing the previously untested SPINOL based phosphoric acids host family, an in depths study of the parameters affecting the efficiency of the resolution of amino-alcohols in the optic of further understanding the core principles behind ELLE. We have systematically investigated the dependencies of the enantioselection by parameters such as the choice of solvent, the temperature, as well as the pH and bring to light many previously unsuspected and highly intriguing interactions. Furthermore, utilizing these new insights to our advantage, we developed novel, highly efficient, extraction and resolving protocols which provide remarkable levels of enantioselectivity. It was shown that the extraction is catalytic in host by demonstrating transport in a U-tube and finally it was demonstrated how the solvent dependency could be exploited in an unprecedented triphasic resolution system.
Challenge toward structural complexity using asymmetric catalysis: Target-oriented development of catalytic enantioselective Diels-Alder reaction
Usuda, Hiroyuki,Kuramochi, Akiyoshi,Kanai, Motomu,Shibasaki, Masakatsu
, p. 4387 - 4390 (2007/10/03)
(Chemical Equation Presented) A new method for the catalytic enantioselective Diels-Alder reaction using polysubstituted silyl enol ethers as dienes is described. High enantioselectivity (up to 92% ee) was produced using a catalyst generated from FeBr3 and AgSbF6 in a 1:2 ratio and aryl-pybox (aryl = Ph or p-ethoxyphenyl). This reaction should facilitate the enantioselective synthesis of polycyclic acylphloroglucinols such as hyperforin or garsubellin A, which are currently of interest from synthetic and medicinal points of view.
Palladium(II) complexes of chiral tridentate nitrogen pybox ligands
Nesper, Reinhard,Pregosin, Paul,Puentener, Kurt,Woerle, Michael,Albinati, Alberto
, p. 85 - 101 (2007/10/03)
A series of mono-and di-cationic palladium(II) complexes containing different chiral tridentate nitrogen ligands, pybox, have been prepared [pybox = 2,6-bis[4′-(S)-iPr (or Ph, or Bz or p-EtOC6H4)oxazoline-2′-y1]pyridine (1-4), respectively]. The molecular structures for two of these, [Pd(CH3CN)(2)](BF4)2 (6) and [Pd(PPh3)(3)](BF4)2 (21g), have been determined by X-ray diffraction and show no major steric hindrance in the fourth coordination position. In connection with the aldol reaction of CNCH2CO2Me with PhCHO, several new isonitrile PdII complexes have also been prepared. It is shown that, under catalytic conditions, the chiral tridentate pybox ligand is completely displaced, thus explaining its failure as a chiral auxiliary. Preparative details for a series of chiral Pd(L)(3)n+(BF4)n (21) complexes [L = 4-methylpyridine, 2,6-dimethylpyridine, 4-methyl aniline, H2NCH2CH(OMe)2, H2NCH2CH2OH, H2N(CH2)5CH3, N-3, HCO-2, Cl-] are given, as are preparative details for some model PdII acetonitrile complexes with chiral phosphorus and nitrogen chelating ligands. For 6, i.e. PdC25H22N4O2B2F8, the crystals are monoclinic with space group P21 (No. 4), a = 13.582(6) A, b = 13.826(6) A, c = 14.667(6) A, β = 97.28(3)°°, V = 2732(2) A3, Z = 4. For 21g, i.e. C43H38B2F8N3O2P2Pd, the crystals are orthorhombic with space group, P212121, a = 10.616(4) A, b = 16.774(2) A, c = 23.086(4) A, V = 4111(3) A3, Z = 4.
