title: Synthesis of spirofused carbohydrate-oxazoline based palladium(II) complexes.
abstract: Four carbohydrate-derived 2-pyridyl and 2-quinolinyl substituted spiro-oxazoline ligands were prepared from 3,4,5-tri-O-benzyl-1,2-di-O-isopropylidene-β-D-fructose in four steps. Conversion of the latter compound with trimethylsilylazide followed by hydrogenation gave an anomeric mixture of 2-amino-3,4,5-tri-O-benzyl-2-deoxy-1-O-trimethylsilyl-D-fructopyranose. Amide coupling of the fructosylamines with picolinic acid and quinaldic acid, respectively afforded the corresponding anomeric amidofructosides, which were both separated and characterized by NMR spectroscopy and X-ray crystallography. Cyclization of alpha-amides was achieved by treatment of the corresponding mesylates with NaH while beta-amides were directly cyclisized with NCS and Ph3P to give the corresponding 2-pyridyl (PyOx) and 2-quinolyl (QuinOx) substituted spiro-oxazoline ligands, respectively. The 2-pyridyl substituted spiro-oxazoline ligands PyOx formed stable complexes with Pd(II), which were fully characterized and their structure determined by X-ray crystallography, whereas the corresponding QuinOx ligands failed to form similar Pd complexes.
authors.affiliation: Institute of Organic Chemistry, University of Tuebingen, Auf der Morgenstelle 18, 72076 Tuebingen, Germany.
authors.forename: Jochen
authors.initials: J
authors.lastname: Kraft
authors.affiliation: Institute of Organic Chemistry, University of Tuebingen, Auf der Morgenstelle 18, 72076 Tuebingen, Germany. Electronic address: thomas.ziegler@uni-tuebingen.de.
authors.forename: Thomas
authors.initials: T
authors.lastname: Ziegler
mesh_terms: D002236:Carbohydrate Conformation; D002384:Catalysis; D056831:Coordination Complexes / Q000138:chemical synthesis*; D018360:Crystallography, X-Ray; D003500:Cyclization; D008024:Ligands; D008958:Models, Molecular; D010080:Oxazoles / Q000138:chemical synthesis*; D010165:Palladium / Q000737:chemistry*; D013141:Spiro Compounds / Q000138:chemical synthesis*
chemical_list: D056831:Coordination Complexes; D008024:Ligands; D010080:Oxazoles; D013141:Spiro Compounds; D010165:Palladium
keywords: Asymmetric catalysis; Carbohydrates; Cyclization; Palladium; Pyridines; Spiro compounds