A general method for copper-catalyzed arylation of sp 2 C-H bonds with pKa's below 35 has been developed. The method employs aryl halide as the coupling partner, lithium alkoxide or K 3 PO 4 base, and DMF, DMPU, or mixed DMF/xylenes solvent. A variety of electron-rich and electron-poor heterocycles such as azoles, caffeine, thiophenes, benzofuran, pyridine oxides, pyridazine, and pyrimidine can be arylated. Furthermore, electron-poor arenes possessing at least two electronwithdrawing groups on benzene ring can also be arylated. Two arylcopper-phenanthroline complex intermediates were independently synthesized.

Olefin metathesis catalysts provide access to molecules that are indispensable to physicians and researchers in the life sciences. A persisting problem, however, is the dearth of chemical transformations that directly generate acyclic Z allylic alcohols, including products that contain a hindered neighbouring substituent or reactive functional units such as a phenol, an aldehyde, or a carboxylic acid. Here we present an electronically modified ruthenium-disulfide catalyst that is effective in generating such high-value compounds by cross-metathesis. The ruthenium complex is prepared from a commercially available precursor and an easily generated air-stable zinc catechothiolate. Transformations typically proceed with 5.0 mole per cent of the complex and an inexpensive reaction partner in 4-8 hours under ambient conditions; products are obtained in up to 80 per cent yield and 98:2 Z:E diastereoselectivity. The use of this catalyst is demonstrated in the synthesis of the naturally occurring anti-tumour agent neopeltolide and in a single-step stereoselective gram-scale conversion of a renewable feedstock (oleic acid) to an anti-fungal agent. In this conversion, the new catalyst promotes cross-metathesis more efficiently than the commonly used dichloro-ruthenium complexes, indicating that its utility may extend beyond Z-selective processes.

Rationally designed Ru-based catalysts for efficient Z-selective olefin metathesis are featured. The new complexes contain a dithiolate ligand and can be accessed in a single step from commercially available precursors in 68-82% yield. High efficiency and exceptional Z selectivity (93:7 to >98:2 Z:E) were achieved in ring-opening metathesis polymerization (ROMP) and ring-opening/cross-metathesis (ROCM) processes; the transformations typically proceed at 22 °C and are operationally simple to perform. Complete conversion was observed with catalyst loadings as low as 0.002 mol %, and turnover numbers of up to 43,000 were achieved without rigorous substrate purification or deoxygenation protocols. X-ray data and density functional theory computations provide support for key design features and shed light on mechanistic attributes.

Investigations on optical and dielectric properties of hybrid ultrathin layer-by-layer (LbL) films of gold nanoparticles (AuNPs) and polyelectrolytes under different pH conditions resulted in surface plasmon resonance (SPR) signal enhancement under attenuated total reflection (ATR) spectroscopy conditions. Theoretical considerations on the basis of the Maxwell-Garnett theory were made to compare with experimental results. LbL films with different layer architectures were fabricated from AuNPs and two polyelectrolytes: poly-(allylamine hydrochloride) (PAH) and poly(styrene sulfonate) (PSS) on Au and Ag thin film substrates for ATR. UV-vis spectroscopy and SPR spectroscopy were applied to study LbL film growth and monitor SPR shift upon pH switching. The (PAH/AuNPs) x multilayers showed an interesting dual-responsive SPR change as a function of pH and distance between AuNP layers and metal film. The addition of (PAH/PSS) y layers was found to act as an effective cushion to enhance this SPR response due to the significant swelling/shrinking of the film. In the case of [(PAH/PSS) y + (PAH/AuNPs) x ], both theoretical calculations and experimental results showed that the SPR response can either (a) move toward lower incident angle with a sharp peak shape upon swelling in pH ) 2 or (b) shift to a higher angle with a broadened peak shape after contraction in pH ) 10. This effect was found to be opposite to what is expected from LbL films made up of the polyelectrolytes alone. Moreover, increasing the distance between AuNPs and the metal films also decouples this enhancement effect. A two-wavelength experiment (red and green lasers) was used to quantitatively demonstrate this SPR response to pH switching. Finally, SPR imaging was employed to monitor the SPR change with pH switching between 2 and 10 on the [(PAH/PSS) 4 + (PAH/AuNPs) 2 ] film. Thus, on the basis of the SPR spectroscopic and SPR imaging pH response, a reproducible and stable sensing system can be successfully fabricated with these films.