O/W Pickering emulsions stabilized by cocoa powder: Role of the emulsification process and of composition parameters.

We fabricated oil-in-water emulsions stabilized by delipidated commercial cocoa powder. The emulsions were characterized in terms of droplets and particles size distribution and interfacial coverage by cocoa powder by developing methods to separate droplets from adsorbed and unadsorbed cocoa particles. Three different processes were compared for their ability to produce fine and stable emulsions: rotor/stator turbulent mixing, sonication and microfluidization. Among those techniques, microfluidization was the most performing one. In this case, micron-sized emulsions with narrow size distributions could be obtained with >90 wt% of the powder insoluble material anchored to the interfaces, and they were still stable after 90 days. It was demonstrated that the mixing process did not generate finer cocoa particles but provoked disentanglement of the large primary particles, providing them an open, expanded structure that facilitated emulsification. It was also shown that the finer insoluble fraction of the powder and the soluble fraction had no significant impact on emulsification and on kinetic stability. In the poor particles regime, the oil-water interfacial area varied linearly with the amount of adsorbed powder, suggesting that the final droplet size was controlled by the so-called limited coalescence process, as already observed in conventional Pickering emulsions stabilized by spherical solid particles.

Oxidative C-H homodimerization of phenylacetamides.

A range of secondary and tertiary phenylacetamides undergo oxidative homodimerization to afford biaryls. The reaction proceeds under palladium catalysis in the presence of a copper cocatalyst and oxygen and is most effective for electron-rich substrates.

The benzyne Fischer-indole reaction.

A new approach to the Fischer-indole synthesis is reported that uses the reactive intermediate benzyne. The addition of N-tosyl hydrazones to arynes, generated through fluoride activation of 2-(trimethylsilyl)phenyl triflate precursors, leads to efficient N-arylation. Addition of a Lewis acid to the same reaction pot then affords N-tosylindole products via Fischer cyclization.

Intramolecular oxidative C-H coupling for medium-ring synthesis.

An oxidative C-H coupling is described for medium-ring synthesis.

Insertion of benzene rings into the amide bond: one-step synthesis of acridines and acridones from aryl amides.

Insertion of benzene rings into the amide bond using the reactive intermediate benzyne is described. Aromatic amides undergo smooth insertion when treated with O-triflatophenyl silane benzyne precursors, producing versatile aminobenzophenone products in good to excellent yield. The process is entirely metal-free and has been exemplified on the synthesis of biologically active acridones and acridines.