Photo-induced catalytic halopyridylation of alkenes

The Mizoroki-Heck reaction and its reductive analogue are staples of organic synthesis, but the ensuing products often lack a chemical handle for further transformation. Here we report an atom-economical cross-coupling of halopyridines and unactivated alkenes under photoredox catalysis to afford a series of alkene halopyridylation products. This protocol with mild and redox neutral conditions contributes broad substrate scope. As a complement to conventional Heck-type reaction, this radical process avoids the involvement of β-H elimination and thus useful pyridyl and halide groups could be simultaneously and regioselectively incorporated onto alkenes. The success depends on TFA-promoted domino photocatalytic oxidative quenching activation and radical-polar crossover pathway. Plausible mechanism is proposed based on mechanistic investigations. Moreover, the reserved C − X bonds of these products are beneficial for performing further synthetic elaborations.

Synergy between Indoloquinolines and Ciprofloxacin: An Antibiofilm Strategy against Pseudomonas aeruginosa

Antibiotic treatments can participate in the formation of bacterial biofilm in case of under dosage. The interest of indoloquinoline scaffold for drug discovery incited us to study the preparation of new indolo [2,3-b]quinoline derivatives by a domino radical process. We tested the effect of two different “indoloquinoline” molecules (Indol-1 and Indol-2) without antimicrobial activity, in addition to ciprofloxacin, on biofilm formation thanks to crystal violet staining and enumeration of adhered bacteria. This association of ciprofloxacin and Indol-1 or Indol-2 attenuated the formation of biofilm up to almost 80% compared to ciprofloxacin alone, or even prevented the presence of adhered bacteria. In conclusion, these data prove that the association of non-antimicrobial molecules with an antibiotic can be a solution to fight against biofilm and antibiotic resistance emergence.

Worsening Shades

Beckett’s late prose texts Company, Ill Seen Ill Said, and Worstward Ho perform a radical process of literary reimagination late in a long writing career: they reconfigure how biography relates to narrative, and they rethink the dimensionality and mobility of character. In their negotiations with literary history and etymology these texts replenish the stocks of language across the deep time of its evolution and its accrual of semantic and associative richness. In their rich geological and archaeological dispositions, the three texts of Nohow On demonstrate how deep time intersects with the narrative present in images of the earth, providing a locus for life and afterlife: both in the sense of the posthumous condition and in offering belated aesthetic possibilities.

Vapor Phase Hydroxyl- or Chlorine-radical Treatment for Inactivating Listeria monocytogenes on Mushrooms (Agaricus bisporus) Without Negatively Affecting Quality or Shelf-life

Processes based on generating vapor phase hydroxyl-radicals or chlorine-radicals were developed for inactivating Listeria monocytogenes on mushrooms without negatively affecting quality. Antimicrobial radicals were generated from the UV-C degradation of hydrogen peroxide or hypochlorite and ozone gas. Response Surface Modelling (RMS) was used to identify the interaction between the operating parameters for the hydroxyl-radical process; UV-C 254nm intensity, hydrogen peroxide concentration and ozone delivered. There was an inverse relationship between hydrogen peroxide concentration and UV-C intensity in terms of the log reduction of L. monocytogenes . The independent parameters for the chlorine-radical process were hypochlorite concentration, pH, and UV-C intensity. From predictive models, the optimal hydroxyl-radical treatment was found to be 5% v/v H 2 O 2 , 2.86 mW/cm 2 UV-C intensity (total UV-C dose 144 mJ/cm 2 ) and 16.5 mg ozone. The chlorine-radical optimal process parameters were 10 ppm hypochlorite (pH 3.0), ozone 11.0 mg and 4.60 mW/cm 2 UV-C intensity. When inoculated mushrooms were treated with the optimal hydroxyl-radical and chlorine-radical process the log CFU reduction of L. monocytogenes was found to be 2.42±0.42 and 2.61±0.30 log CFU respectively without any negative effects on mushroom quality (weight loss and Browning Index during 14 days storage at 4°C). The levels of L. monocytogenes inactivation were significantly greater compared to when the individual elements of the radical processes were applied and control using a 90 s dip in 1% v/v hydrogen peroxide. The study has demonstrated that both hydroxyl-radical and chlorine-radical vapor-phase treatments are both equally effective at inactivating L. monocytogenes on mushrooms and can be considered as a preventative control step.

The Over-Riding Role of Autocatalysis in Allylic Oxidation

In this paper we aim to highlight the need to consider the possible role of autocatalysis in oxidation reactions when using molecular oxygen as the terminal oxidant. Oxygen in its ground state is a diradical, and depending on the reaction conditions, it can initiate oxidation through radical pathways through mechanisms which do not require the presence of a catalyst. Consequently, we contrast the oxidation of benzyl alcohol with oxidation of α-pinene. For benzyl alcohol oxidation the initial reaction is the oxidative dehydrogenation to form benzaldehyde, a non-radical process; but the subsequent over-oxidation to benzoic acid is a radical process. In this case the role of the autocatalysed reaction can be minimised. With α-pinene, the oxidation reaction is via radical pathways and now the autocatalysed reaction can be dominant and, indeed, can be the preferred pathway for the formation of high yields of the desired verbenone product. Graphic Abstract