Iridium complexes containing the first sugar dithioether ligands. Application as catalyst precursors in asymmetric hydrogenation

Abstract

The first family of sugar derivative dithioethers 1,2-O-isopropylidene-3,5-bis(methylsulfanyl)-, (ϩ)-RiSSMe 2 , 1,2-Oisopropylidene-3,5-bis(isopropylsulfanyl)-, (ϩ)-RiSSPr i 2 , and 1,2-O-isopropylidene-3,5-bis(phenylsulfanyl)-α--(ϩ)ribofuranose, (ϩ)-RiSSPh 2 , was prepared from 1,2-O-isopropylidene-3,5-di-O-trifluoromethanesulfonyl--xylofuranose. Reaction of these chiral C 1 symmetrical dithioether ligands with [Ir(cod) 2 ]BF 4 (cod = 1,5-cyclooctadiene) yielded the iridium complexes [Ir(cod){(ϩ)-RiSSR 2 }]BF 4 1-3. Their reaction with H 2 at 0 ЊC gave the cis-dihydridoiridium() complexes [IrH 2 (cod){(ϩ)-RiSSR 2 }]BF 4 4-6. Complexes 1-3 were tested in the asymmetric hydrogenation of acrylic acid derivatives at 1 bar of H 2 and room temperature, providing enantioselectivities of up to 62%.

Molybdenum(vi) cis-dioxo complexes bearing sugar derived chiral Schiff-base ligands: synthesis, characterization, and catalytic applications

“…6 Carbohydrates are naturally occurring enantiomeric pure compounds ("chiral pool") 7 that might be of interest in metalassisted or metal-catalyzed enantioselective synthesis. See http://www.rsc.org/suppdata/dt/ b3/b306039j/ iridium-dithioether complexes 13 and allylic alkylation with palladium complexes. 8 Furthermore, strategies for saccharide ligand modification have also been developed in order to make the isolation and characterization of the products more straightforward.…”

“…Among the few examples yet known are the hydroformylation of styrene with Rh()-diphosphine complexes, 11 catechol oxidation with Cu()-aminocarbohydrate β-ketoenaminic complexes, 12 hydrogenation with † Electronic supplementary information (ESI) available: Analytical and spectroscopic data for ligand 1 and ORTEPS with selected bond lengths and angles for compounds 2 and 3. See http://www.rsc.org/suppdata/dt/ b3/b306039j/ iridium-dithioether complexes 13 and allylic alkylation with palladium complexes. 14 However, despite some sugar derived ligands coordinated to cis-MoO 2 2ϩ moieties have been reported recently, 9 the potential of this class of compounds as catalysts for olefin epoxidation, has not been, to the best of our knowledge, so far explored.…”

Chiral Schiff base Ligated Dioxomolybdenum (VI) Complexes and their Asymmetric Catalytic Properties in the Epoxidation of Styrene

“…[7][8][9] As a cheap and naturally occurring chiral compound, Dglucosamine has been used to synthesise stable Schiff bases complexes with transition-metal ions such as Fe(III), Co(II), Ni(II), Cu(II) and Mo(VI). 10 Metal complexes derived from carbohydrates are of interest in metal-assisted or metalcatalysed enantioselective synthesis such as cyclopropanation, 11 hydroformylation, 12 hydrogenation 13 and allylic alkylation 14 but the potential of this class of complexes as catalysts for enantioselective epoxidation of olefins still remains sparse. 15,16 We now report four kinds of dioxomolybdenum(VI) complexes with Schiff base ligands derived from D-glucosamine and their catalytic activities for asymmetric epoxidation of styrene.…”

Ir(I) complexes with oxazoline-thioether ligands: nucleophilic attack of pyridine on coordinated 1,5-cyclooctadiene and application as catalysts in imine hydrogenation

“…Moreover, a new stereogenic center is created when the sulfur is coordinated to the metal center, which gives rise to diastereomeric mixtures. This behaviour has previously been described for Rh [23] and Pd [24] complexes with thioether ligands. Attempts to obtain crystals suitable for X-ray diffraction were unsuccessful.…”