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The asymmetric Heck reaction is a powerful method for the synthesis of both tertiary and quaternary chiral carbon centers, with an enantiomeric excess often greater than 80%, and in some cases much higher (up to 99% ee). A variety of carbocyclic and heterocyclic systems can be constructed, including spirocyclic systems. The scope of the reaction with respect to the product alkene isomerization is somewhat limited by problems of regioselectivity, however, these problems are surmountable, and a new generation of ligands that dissociate more rapidly from the products, might improve both enantio- and regiocontrol. A variety of chiral compounds prepared by the asymmetric Heck reaction were successfully utilized in the enantioselective syntheses of complex natural products.

The catalytic enantioselective meso-epoxide ring opening reaction with phenolic oxygen nucleophile (4-methoxyphenol) is described for the first time herein. This reaction was first found to be promoted by (R)-GaLB (Ga = gallium, L = lithium, B = (R)-BINOL), giving a variety of epoxide opening products in good to high ee (67−93% ee). However, chemical yield was only modest (yield 31−75%), despite the use of more than 20 mol % GaLB. This was due to the undesired ligand exchange between BINOL and 4-methoxyphenol, which resulted in the decomplexation of GaLB. Application of various known chiral ligands such as 6,6‘-bis((triethylsilyl)ethynyl)-BINOL and H8-BINOL were examined, but satisfactory results were not obtained. To overcome this problem a novel linked-BINOL containing coordinative oxygen atom in the linker has been developed. By linking two BINOL units in GaLB, the stability of the Ga-complex was greatly improved. Using 3−10 mol % (R,R)-Ga-Li-linked-BINOL complex, a variety of epoxide opening reactions...

The enantioselective Heck reaction is a powerful method for the synthesis of both tertiary and quaternary chiral carbon centres, with enantiomeric excesses (ees) often around 80% and in some cases much higher. A variety of carbocyclic and heterocyclic systems can be constructed or modified including spirocyclic systems. Although problems of regioselectivity with respect to the product alkene continue to limit the scope of the reaction somewhat, there are indications that these may be surmountable and that a new generation of ligands and a refined methodology, may improve both enantio- and regiocontrol. All the relevant literature is discussed.

The synthesis of new C 2 -symmetric chiral ligands consisting of two binaphthol units linked by a short bridge is described. These ligands can be used for investigating catalytic asymmetric reactions which utilize BINOL or related ligands as was demonstrated for the ring opening reaction of cyclohexene oxide with 4-methoxyphenol.

4,6-Bis(diphenylphosphanyl)dibenzofuran (1), despite its large P…P distance of 5.74 A and its bite angle of ca. 131° was found to be Capable of tridentate coordination to ruthenium (II) chloride. Single crystal X-ray structure analyses of the new ruthenium (II) complexes 3,4 and 5 revealed that the ligand 1 coordinates to a single ruthenium atom with both phosphorus centers and the dibenzofuran oxygen atom. The remarkable ligand deformation resulting from the coordination is evident from the decrease of the P…P distance by 1 A to 4.75 A and the increase of the bite angle (P–Ru–P) by 25° to 155°−157. The unprecedented in-plane coordination of the dibenzofuran oxygen atom to ruthenium is interesting in view of the hybridisation of the oxygen.

Acid-treated carbon nanotubes have been decorated with nanoscale Au, Pt and Ag clusters by employing several procedures. The nature and extent of metal coverage can be varied by changing the concentration of the metal compound or by mild sonication (treatment with ultrasound). The metal clusters seem to get deposited on the acidic surface sites of the nanotubes.

Reaction of Co2(CO)8 with 4,6-bis(diphenylphosphino)dibenzofuran (1) in diethylether gives the dinuclear complex 4,6-bis(diphenylphosphino)dibenzofurandicobalthexacarbonyl (2). The solid state structures of 1 and 2 have been established by X-ray crystallography. Low temperature 13C-NMR spectroscopy was used to analyse 2 in solution.

The synthesis of new C 2 -symmetric chiral ligands consisting of two binaphthol units linked by a short bridge is described. These ligands can be used for investigating catalytic asymmetric reactions which utilize BINOL or related ligands as was demonstrated for the ring opening reaction of cyclohexene oxide with 4-methoxyphenol.

A general protocol for the Pd-catalyzed-arylation of nitroalkanes is described. Substituted aryl bromides as well as aryl chlorides can be coupled efficiently with a variety of nitroalkanes under mild conditions to selectively yield the monoarylated products. This method tolerates a number of functional groups including ketones, esters, and olefins. Notably, the arylation of nitroalkanes can be effected chemoselectively over ketone and ester arylation.

Hollow nanotubes of SiO2, Al2O3, V2O5, and MoO3 have been prepared using carbon nanotubes as templates. The procedure involves coating the carbon nanotubes with tetraethylorthosilicate, aluminum isopropoxide, or vanadium pentoxide gel, followed by calcination and heating at higher temperatures in air to oxidize the carbon. SiO2 nanotubes containing transition metal ions have been prepared by this procedure since such materials may be of use in catalysis.

Chiral [(salen)Li2·hmpa]2 has a Li4O4 cubane-type core in the solid but low-temperature NMR spectroscopy reveals a racemisation equilibrium in solution; deliberate addition of H2O to [(salen)Li2]n in the presence of tmen produces a species having two Li4O4 cubes sharing a common oxygen and containing tmen ligands acting in a hitherto unobserved monofunctional mode.

A general protocol for the Pd-catalyzed-arylation of nitroalkanes is described. Substituted aryl bromides as well as aryl chlorides can be coupled efficiently with a variety of nitroalkanes under mild conditions to selectively yield the monoarylated products. This method tolerates a number of functional groups including ketones, esters, and olefins. Notably, the arylation of nitroalkanes can be effected chemoselectively over ketone and ester arylation.

Make your catalyst more enantioselective! The enantiomeric excess of a catalytic reaction system can sometimes be enhanced from below 10 to over 90 % by the use of suitable achiral additives. Since completely different mechanisms can influence the catalyst and reaction outcome, there is a range of additives that can be applied to improve the catalyst efficiency for a variety of organic reactions.

Mukaiyamas classic catalytic asymmetric al- dol reaction with enolsilanes has been improved upon over the years; now new approaches to the reaction have been developed. Those reviewed here are the use of new transition metal based catalysts for the aldol reaction using silyl enolates, the use of other O-silylated nucleo- philes, tin-modified or even unmodified ketones as substrates, and the use of chiral nonmetallic Lewis acids or Lewis bases as catalysts.

Objectives To investigate the cytotoxic potential of S. aethiopicus extracts in combination with chitosan and Pharmacel®101, on two cell lines. Methods Extracts were chemically characterised utilising UPLC-Q-TOF/MS, followed by determination of cell viability and membrane integrity. Key findings Ethanol (EtOH) and diethyl ether (DiEt) extracts contained significant quantities of all chosen biomarker molecules; however, only two were scarcely quantifiable in aqueous extracts. Aqueous extracts did not induce any cytotoxic effects, whereas EtOH and DiEt extracts caused concentration-dependent decreases in cell viability and membrane integrity loss in both cell lines. Ensuing exposure to EtOH extracts at 50, 100 and 150 μg/ml, HepG2 cells were considered 15.5%, 12.5% and 32.8% apoptotic, whereas DiEt extracts caused 4.5%, 13.5% and 33.9% apoptotic cells. Exposure to EtOH and DiEt extracts at 50 μg/ml ensued in 20.2% and 21.3% apoptosis in Caco-2 cells; 100 μg/ml induced apoptosis in 19.9% and 10.3% of Caco-2 cells; whereas exposure to 150 μg/ml EtOH extracts caused 12.6% apoptosis compared to 11.7% induced by the DiEt extract. Conclusions None of the excipients caused any significantly altered cellular effects, indicating little chance for physicochemical interactions. Aqueous extracts did not possess any cytotoxic properties. However, it is clear that organic extracts caused apoptotic and necrotic cell death.