299168-49-3Relevant articles and documents
Palladium(II) complexes of chiral tridentate nitrogen pybox ligands
Nesper, Reinhard,Pregosin, Paul,Puentener, Kurt,Woerle, Michael,Albinati, Alberto
, p. 85 - 101 (1996)
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.
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.