While the synthesis of biaryls has advanced rapidly in the past decades, cross-Ullman couplings of aryl chlorides, the most abundant aryl electrophiles, have remained elusive. Reported here is the first general cross-Ullman coupling of aryl chlorides with aryl triflates. The selectivity challenge associated with coupling an inert electrophile with a reactive one is overcome using a multimetallic strategy with the appropriate choice of additive. Studies demonstrate that LiCl is essential for effective cross-coupling by accelerating the reduction of Ni(II) to Ni(0) and counteracting autoinhibition of reduction at Zn(0) by Zn(II) salts. The modified conditions tolerate a variety of functional groups on either coupling partner (42 examples), and examples include a three-step synthesis of flurbiprofen.

While phenols are frequent and convenient aryl sources in cross-coupling, typically as sulfonate esters, the direct cross-Ullmann coupling of two different sulfonate esters is unknown. We report here a general solution to this challenge catalyzed by a combination of Ni and Pd with Zn reductant and LiBr as an additive. The reaction has broad scope, as demonstrated in 33 examples (65% ± 11% average yield). Mechanistic studies show that Pd strongly prefers the aryl triflate, the Ni catalyst has a small preference for the aryl tosylate, aryl transfer between catalysts is mediated by Zn, and Pd improves yields by consuming arylzinc intermediates.

The first AgI‐mediated C–H ethoxycarbonyl difluoromethylation with TMSCF2COOEt (TMS = trimethylsilyl) has been developed. The radical difluoromethylation proceeds smoothly to give the difluoromethylated arenes in moderate to high yields with Friedel–Crafts‐type regioselectivity. Mechanistic studies indicate that the innate C–H difluoromethylation proceeds through an electrophilic radical‐type pathway.

The covalent immobilization of trypsin onto poly[(methyl methacrylate)-co-(ethyl acrylate)-co-(acrylic acid)] latex particles, produced by a soap-free emulsion polymerization technique, was carried out using the carbodiimide method. The catalytic properties and kinetic parameters, as well as the stability of the immobilized enzyme were compared to those of the free enzyme. Results showed that the optimum temperature and pH for the immobilized trypsin in the hydrolysis of casein were 55 degrees C and 8.5, both of which were higher than that of the free form. It was found that K(m) (Michaelis constant) was 45.7 mg . ml(-1) and V(max) (maximal reaction rate) was 793.0 microg . min(-1) for immobilized trypsin, compared to a K(m) of 30.0 mg . ml(-1) and a V(max) of 5 467.5 microg . min(-1) for free trypsin. The immobilized trypsin exhibited much better thermal and chemical stabilities than its free counterpart and maintained over 63% of its initial activity after reusing ten times.

A series of well-defined phosphine-ligated diarylgold­(III) complexes cis-[Au­(L)­(ArF)­(Ar′)­(Cl)] were prepared, and detailed kinetics of the C­(sp2)–C­(sp2) reductive elimination from these complexes were studied. The mechanism of the reductive elimination from the complexes cis-[Au­(L)­(ArF)­(Ar′)­(Cl)] was further studied by theoretical calculations. The combination of experimental and theoretical results suggests that the biaryl reductive elimination from organogold­(III) complexes cis-[Au­(L)­(ArF)­(Ar′)­(Cl)] proceeds through a concerted biaryl-forming pathway from the four-coordinated Au­(III) metal center. These studies also disclose that the steric hindrance of the phosphine ligands plays a major role in promoting the biaryl-forming reductive elimination from diarylgold­(III) complexes cis-[Au­(L)­(ArF)­(Ar′)­(Cl)], while electronic properties of these ligands have a much smaller effect. Futhermore, it was found that the complexes with more weakly electron withdrawing aryl ligands undergo reductive elimination more quickly and the elimination rate is not sensitive to the polarity of the solvents.