A ridge walk between reaction modes: an unprecedented Pd-catalyzed domino sequence of diynyl-substituted bromoarenes

Diynyl-substituted bromoarenes underwent a novel Pd-catalyzed domino reaction to provide benzofurans, pyridinofurans, isochromenes, and indole derivatives. Slight changes of the substrate push the reaction in another direction resulting in benzene annulation.     

Multivariate statistics for the differentiation of erythropoietin preparations based on intact glycoforms determined by CE-MS

Owing to the increasing number of erythropoietin biosimilars being approved, the comparison of different erythropoietin preparations in the pharmaceutical area is gaining in importance. Erythropoietin has a distinct natural heterogeneity arising from its glycosylation, which shows strong composition variations. This heterogeneity increases the complexity of the analysis of erythropoietin considerably, but may also be used to distinguish different preparations. Here, a method is presented for the differentiation of various erythropoietin preparations by capillary electrophoresis–mass spectrometry and the subsequent application of multivariate statistics. Relative peak areas of selected intact erythropoietin isoforms were used as variables in principal component analysis and hierarchical agglomerative clustering. Both of these strategies were suited for the clear differentiation of all erythropoietin preparations, including marketed products and preproduction preparations, which differ in the manufacturer, the production cell line, and the batch number. By this means, even closely related preparations were distinguished on the basis of the combined information on the antennarity, the sialoform, and the acetylation of the observed isoforms.     

The irreversible formation of palladium carbide during hydrogenation of 1-pentyne over silica-supported palladium nanoparticles: in situ Pd K and L3 edge XAS

The catalytically active phase of silica-supported palladium catalysts in the selective and non-selective hydrogenation of 1-pentyne was determined using in situ X-ray absorption spectroscopy at the Pd K and L(3) edges. Upon exposure to alkyne, a palladium carbide-like phase rapidly forms, which prevents hydrogen to diffuse into the bulk of the nano-sized particles. Both selective and non-selective hydrogenation occur over carbided particles. The palladium carbide-like phase is stable under reaction conditions and only partially decomposes under high hydrogen partial pressure. Non-selective hydrogenation to pentane is not indicative of hydride formation. The palladium carbide phase was detected in the EXAFS analysis and the K edge XANES showed representative features.     

Aggregation of donor base stabilized 2-thienyllithium in a single crystal and in solution: distances from X-ray diffraction and the nuclear Overhauser effect

Various 2-thienyllithium derivatives were investigated in the solid state by X-ray diffraction and in solution by 2D NMR experiments. The determined structures of [(Et(2)O)Li(C(4)H(3)S)](4) (1), [(THF)(2)Li(C(4)H(3)S)](2) (2), [(DME)Li(C(4)H(3)S)](2) (3), [(TMEDA)Li(C(4)H(3)S)](2) (4), and [(PMDETA)Li(C(4)H(3)S)] (5) (DME = 1,2-dimethoxyethane, TMEDA = N,N,N',N'-tetramethylethylene-1,2-diamine, and PMDETA = N,N,N',N",N"-pentamethyldiethylenetriamine) were solved in nondonating toluene and provide firm ground for diffusion-ordered NMR spectroscopy as well as heteronuclear Overhauser enhancement NMR spectroscopy. The distance relation of nuclear Overhauser effects with a factor of r(-6) is employed to gain further insight into the aggregation degree of 1-5 in solution. Comparison of the slope provided by the linear region of the buildup curves and of the ∑r(-6) calculated distances from the crystal structures offers a handle to judge the structure retention versus conversion in solution. The structures of 3-5 are maintained in toluene solution. The data of 2, however, indicate a partial dissociation or a rapid exchange between the vertices of a tetrameric core and free THF molecules. Auxiliary exchange spectroscopy investigations showed that the signals of the nitrogen donor base containing compounds 4 and 5 exchange with the signals of nonlithiated thiophene. This is explained by exchange of the deuterium by a hydrogen atom via lithiation of toluene molecules.     

Poly(ionic liquid) complex with spontaneous micro-/mesoporosity: template-free synthesis and application as catalyst support

A facile, template-free synthetic route is reported toward poly(ionic liquid) complexes (PILCs) which for the first time exhibit stable micro-/mesoporous structure. This is accomplished via in situ ionic complexation between imidazolium-based PILs and poly(acrylic acid) in various alkaline organic solvents. The PILC can be highly loaded with copper salts and can be used as a catalytic support for effective aerobic oxidation of activated hydrocarbons under mild conditions.     

Application and Mechanistic Studies of a Water‐Oxidation Catalyst in Alcohol Oxidation by Employing Oxygen‐Transfer Reagents

By using a dimeric ruthenium complex in combination with tert‐butyl hydrogen peroxide (TBHP) as stoichiometric oxidant, a mild and efficient protocol for the oxidation of secondary benzylic alcohols was obtained, thereby giving the corresponding ketones in high yields within 4 h. However, in the oxidation of aliphatic alcohols, the TBHP protocol suffered from low conversions owing to a competing Ru‐catalyzed disproportionation of the oxidant. Gratifyingly, by switching to Oxone (2 KHSO₅ ? KHSO₄ ? K₂SO₄ triple salt) as stoichiometric oxidant, a more efficient and robust system was obtained that allowed for the oxidation of a wide range of aliphatic and benzylic secondary alcohols, giving the corresponding ketones in excellent yields. The mechanism for these reactions is believed to involve a high‐valent Ru^V–oxo species. We provide support for such an intermediate by means of mechanistic studies.     

Synthesis of (S)-(+)-cericlamine through lipase-catalyzed aminolysis of azo acetates

The kinetic enzymatic resolution of azo acetates via aminolysis with Candida antarctica lipase B has been investigated using benzylamine as amine component. The products obtained from this biotransformation in high enantiomeric purity can serve as valuable precursors for various amino alcohols, as exemplified by the synthesis of the serotonin reuptake inhibitor (S)-(+)-cericlamine.