Stereoselective synthesis of hydroxylated 3-aminoazepanes using a multi-bond forming, three-step tandem process

A multi-bond forming, three-step tandem process involving a palladium(II)-catalysed Overman rearrangement and a ring closing metathesis reaction has been utilised for the efficient synthesis of a 2,3,6,7-tetrahydro-3-amidoazepine. Substrate directed epoxidation or dihydroxylation of this synthetic intermediate has allowed the diastereoselective synthesis of hydroxylated 3-aminoazepanes including the syn-diastereomer of the balanol core. Asymmetric synthesis of the 2,3,6,7-tetrahydro-3-amidoazepine motif was also achieved using a chiral palladium(II)-catalyst during the Overman rearrangement

Dichloropalladium complexes ligated by 4,5-bis(arylimino)pyrenylidenes: Synthesis, characterization, and catalytic behavior towards Heck-reaction

A series of 4,5-bis(arylimino)pyrenylidenylpalladium(II) chloride complexes (C1–C4) were synthesized and characterized by FT-IR and NMR spectroscopy, elemental analysis as well as by single crystal X-ray diffraction for the representative complexes C1 and C3, which revealed a square planar geometry at the palladium center. All palladium complexes exhibited high activity for the Heck cross-coupling reaction, which were effective when conducted in various solvents. Furthermore, the in-situ mixture of palladium dichloride and the ligand (L1) provided an effective catalytic system for the Heck-reaction

Glycerol as a cheap, safe and sustainable solvent for the catalytic and regioselective β,β-diarylation of acrylates over palladium nanoparticles

Herein we show that glycerol can be considered as a promising cheap and green solvent for the regioselective β,β-diarylation of alkenes. Whereas this reaction is generally catalyzed under an inert atmosphere by expensive phosphine or carbene-palladium complexes, we show here that the diarylation of alkenes can be conveniently achieved in glycerol in the presence of air-stable palladium nanoparticles. These palladium nanoparticles were stabilized over a sugar-based surfactant derived from biomass. By an adjustment of the reaction temperature, we were able to control the mono- and diarylation step of alkenes, thus offering a convenient route to unsymmetrical diarylated alkenes. At the end of the reaction, the diarylated alkenes were cleanly and selectively extracted from the glycerol-palladium catalytic phase using supercritical carbon dioxide, thus affording a convenient purification work-up. Within the framework of green chemistry, this work combines (i) catalysis in a cheap, safe and sustainable medium, (ii) easily made and air-stable palladium nanoparticles as the catalyst, and (iii) a clean and selective extraction of the reaction products with supercritical carbon dioxide

The complexes of palladium (II) and nickel (II) with cycloalkanecarboxylic acid

Although some organic hydroxy acid complexes of palladium(II) and nickel(II) have been described (1-9), crystalline palladium(II) and mickel(II) dicycloalkanecarboxylates have not been reported. The interaction of a palladium salt such as NA2PdCl4 or a nickel salt such as NiCl2·6H2 with cycloalkane carboxylic acids which contain 3, 4, 5, 6, and 7 carbons produces deep green carboxylates with palladium(II) and yellowish green carboxylates with nickel(II)

Structure/activity relationships applied to the hydrogenation of α,β-unsaturated carbonyls: The hydrogenation of 3-butyne-2-one over alumina-supported palladium catalysts

The gas phase hydrogenation of 3-butyne-2-one, an alkynic ketone, over two alumina-supported palladium catalysts is investigated using infrared spectroscopy in a batch reactor at 373 K. The mean particle size of the palladium crystallites of the two catalysts are comparable (2.4 ± 0.1 nm). One catalyst (Pd(NO3)2/Al2O3) is prepared from a palladium(II) nitrate precursor, whereas the other catalyst (PdCl2/Al2O3) is prepared using palladium(II) chloride as the Pd precursor compound. A three-stage sequential process is observed with the Pd(NO3)2/Al2O3 catalyst facilitating complete reduction all the way through to 2-butanol. However, hydrogenation stops at 2-butanone with the PdCl2/Al2O3 catalyst. The inability of the PdCl2/Al2O3 catalyst to reduce 2-butanone is attributed to the inaccessibility of edge sites on this catalyst, which are blocked by chlorine retention originating from the catalyst’s preparative process. The reaction profiles observed for the hydrogenation of this alkynic ketone are consistent with the site-selective chemistry recently reported for the hydrogenation of crotonaldehyde, an alkenic aldehyde, over the same two catalysts. Thus, it is suggested that a previously postulated structure/activity relationship may be generic for the hydrogenation of α,β-unsaturated carbonyl compounds over supported Pd catalysts

Producing Dihydrofurans Using Palladium (II) Catalyst and Optimized Base

Dihydrofurans serve as building blocks for other compounds in organic synthesis. The main goal of this project was to discover an efficient and relatively inexpensive pathway for producing monosubstituted dihydrofurans in high yield from cyclic boronic half acids. Aldehydes were converted to homoallylic alcohols by the addition of allylmagnesium bromide. The alcohols were then transformed into cyclic boronic half acids using ringclosing metathesis with Grubbs 1st Generation Catalyst and alkenyl boronic esters. Finally, monosubstituted dihydrofurans were produced using a palladium (II) catalyst with a base. Palladium (II) catalysts that were tested include [1,1\u27- bis(diphenylphosphino)ferrocene]palladium (II) dichloride, palladium (II) acetate with and without triphenylphosphine, palladium (II) chloride with and without triphenylphosphine, and bis(triphenylphosphine)palladium(II) dichloride. The effect of an alkyl halide on dihydrofuran yield due to Suzuki-Miyaura coupling side product formation was also observed using 1-bromo-3-phenylpropane. Due to time constraints potassium carbonate was the only base that was tested. The results indicate that dihydrofuran production is possible with various palladium (II) catalysts using potassium carbonate as a base. Palladium (II) acetate with the addition of triphenylphosphine appears to form dihydrofuran in the highest yield

Simultaneous Determination of Palladium(II) and Gold(III) in Mixtures by Third Derivative Spectrophotometry Using 3-Hydroxy-2-methyl-1-phenyl-4-pyridone Ligand

A spectrophotometric method has been developed for the determination of microgram amounts of palladium(II). The method is based on the extraction of palladium(II) by a chloroform solution containing 3-hydroxy-2-methyl-1-phenyl-4-pyridone (HX). Palladium(II) was highly extracted with HX from aqueous sulphuric acid media. The extraction took place in the pH range 1.5–3.0. The chloroform layer was applicable for the spectrophotometric determination of palladium( II). Molar absorptivity was 1.89 × 104 mol–1 dm3 cm–1 at 345 nm. Use of the third-derivative spectrophotometry enables determination of palladium(II) and gold(III) in their mixture without previous separation. Palladium(II) was thus determined in the concentration range 0.28–8.0 µg cm–3 (in the presence of 1.0–8.0 µg cm–3 gold), and gold(III) was determined in the range 1–13.0 µg cm–3 (in the presence of 1–5 µg cm–3 of palladium). The method was successfully applied for the determination of palladium in synthetic mixtures and in Pd-charcoal

Simultaneous Determination of Palladium(II) and Gold(III) in Mixtures by Third Derivative Spectrophotometry Using 3-Hydroxy-2-methyl-1-phenyl-4-pyridone Ligand

A spectrophotometric method has been developed for the determination of microgram amounts of palladium(II). The method is based on the extraction of palladium(II) by a chloroform solution containing 3-hydroxy-2-methyl-1-phenyl-4-pyridone (HX). Palladium(II) was highly extracted with HX from aqueous sulphuric acid media. The extraction took place in the pH range 1.5–3.0. The chloroform layer was applicable for the spectrophotometric determination of palladium( II). Molar absorptivity was 1.89 × 104 mol–1 dm3 cm–1 at 345 nm. Use of the third-derivative spectrophotometry enables determination of palladium(II) and gold(III) in their mixture without previous separation. Palladium(II) was thus determined in the concentration range 0.28–8.0 µg cm–3 (in the presence of 1.0–8.0 µg cm–3 gold), and gold(III) was determined in the range 1–13.0 µg cm–3 (in the presence of 1–5 µg cm–3 of palladium). The method was successfully applied for the determination of palladium in synthetic mixtures and in Pd-charcoal

Synthesis of a [2]rotaxane through first- and second-sphere coordination

In an effort to expand the application of a new template from interpenetrated to interlocked molecular species, we report the synthesis of a new [2]rotaxane by means of both first- and second-sphere coordination of a palladium(II) dichloride subunit