New ruthenium metathesis catalysts with chelating indenylidene ligands: synthesis, characterization and reactivity

Six new ruthenium complexes bearing a bidentate (κ(2)O,C)-isopropoxy-indenylidene and PPh(3) or PCy(3) ligands have been synthesized and characterized by (1)H, (13)C NMR spectroscopy and X-ray crystallography. Some of these complexes were synthesized in dimethyl carbonate, a green solvent that was recently shown to be suitable for several catalytic transformations including olefin metathesis. The thermal stability and catalytic efficiency of the PCy(3)-containing complexes have been evaluated in a series of test reactions.     

Efficient aqueous-phase Suzuki coupling of activated aryl chlorides with arylboronic acids using d-glucosamine-based dicyclohexylarylphosphine

The synthesis of a new d-glucosamine-based dicyclohexylarylphosphine has been developed. The catalytic performance of this neutral ligand is demonstrated in the Suzuki-Miyaura cross-coupling reaction between several arylboronic acids and aryl or heteroaryl chlorides.     

Dichloro(diisopropylamino)phosphonio[5(4H)oxopyrazol‐4‐ylide‐5‐one]: Synthesis and properties

Chlorination of the 4‐[chloro(diisopropylamino)phosphino]pyrazole 1 leads to the dichlorophosphonium chloride 2 , which immediately after its formation transforms into the dichloro(diisopropylamino)phosphonio[5(4)oxopyrazol‐4‐ylide‐5‐one] 3 , as a result of dealkylation through loss of ethyl chloride. Reactions of 3 with various nucleophilic reagents were studied. The partial hydrolysis of 3 in the presence of nitriles, resulting in new phosphorus‐containing cyclic systems, is of particular interest. It was demonstrated that chlorination of the P‐dichloropyrazolylphosphine A leads to the stable tetrachlorophosphorane 12 . The C P bond of 12 is broken upon heating. An X‐ray structure determination of compound 11b revealed a planar central heterocycle (mean deviation 0.029 Å). © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:452–458, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10177     

Dealkylation of 4-phosphorylated 5-alkoxypyrazoles: Easy synthetic access to P-chloro ylides

The chlorination of 5-alkoxypyrazoles containing bis-(dialkylamino)- or diphenylphosphino groups at the4-position afforded highly unstable chlorophosphoni-um chlorides that dealkylated giving chlorobis(di-alkylamino)- and chlorodiphenylphosphonium(3-methyl-5-oxo-1-phenyl-5H-pyrazol-4-yl)ides. The P-chloro ylides do not react with aromatic aldehydes, but chlorine atoms are easily substituted with OH, NH₂ ArNH, and Et₂N residues. They also exhibit basic properties and add hydrogen chloride with protonation at N-2. © 1998 John Wiley & Sons, Inc. Heteroatom Chem 9:41–49, 1998     

Ruthenium–Indenylidene Olefin Metathesis Catalyst with Enhanced Thermal Stability

Two new ruthenium complexes bearing a bidentate (κ²O,C)‐isopropoxy–indenylidene ligand and a PPh₃ ( 9 ) or PCy₃ ( 10 , Cy=cyclohexyl) ligand have been synthesized and fully characterized by ¹H and ¹³C NMR spectroscopy and X‐ray crystallography. Complex 10 displays a very high thermal stability with a half life of six days at 110 °C in [D₈]toluene. Complex 10 was evaluated in various ring‐closing metathesis reactions and ring‐opening metathesis polymerization of dicyclopentadiene, in which it showed a latent behavior with low activity at room temperature and high activity upon thermal activation.     

Biomass conversion to high value chemicals: from furfural to chiral hydrofuroins in two steps

Catalytic asymmetric transfer hydrogenation of rac-furoin and furil produces hydrofuroin with up to 99% ee and 9:1 dr. This reaction provides an exceptionally easy access to optically active hydrofuroins in two straightforward steps from biomass-derived furfural (global production 200?000-300?000 t annually) using benzoin condensation.