Catalytic Intermolecular Functionalization of Benzimidazoles

This chapter describes contemporary strategies for selective catalytic intermolecular functionalization of the benzimidazole scaffold. Functionalization at nitrogen and position C-2 is well developed employing copper, palladium, rhodium, nickel, and cobalt catalysis. Direct CH activation is the predominant approach to C-2 functionalization. Nickel-based catalysts can activate C—O bonds in conjunction with C—H activation at benzimidazole which grants access to a very broad range of phenols and enols as convenient functionalization precursors in this chemistry. The remaining carbon positions of benzimidazoles are typically functionalized via a sequential halogenation/coupling strategy to ensure selectivity. A key success factor in enabling these chemistries has been the fine-tuning of catalyst-ligand combinations

A Green, Scalable, and Catalyst-Free One-Minute Synthesis of Quinoxalines

A highly efficient and catalyst-free protocol is reported for the synthesis of quinoxalines via the classical cyclocondensation reaction between aryldiamines and dicarbonyl compounds. Remarkably simple and green reaction conditions employing methanol as solvent afforded medium to excellent yield of quinoxalines after only one-minute reaction time at ambient temperature. The conditions allow at least 10 gram scale synthesis of quinoxalines and should be a preferred starting point for optimization and method of choice for applications in the synthetic community

Heterocyclic cellular lipid peroxidation inhibitors inspired by the marine antioxidant barettin

Accepted manuscript version. Published version available at https://doi.org/10.1016/j.bioorg.2018.11.024. Licensed CC BY-NC-ND 4.0.The marine environment remains a rich source for the discovery and development of novel bioactive compounds. The present paper describes the design, synthesis and biological evaluation of a library of small molecule heterocyclic mimetics of the marine 2,5-diketopiperazine barettin which is a powerful natural antioxidant. By mainly focusing on the influence from the brominated indole and heterocyclic core of barettin, a library of 19 compounds was prepared. The compounds comprised a heterocyclic core, either a 2,5 diketopiperazine, an imidazolidinedione or a thioxothiazolidinone, which were mainly monosubstituted with ranging bulky substituents. The prepared compounds were screened for activity in a cellular lipid peroxidation assay using HepG2 cells. Several of the synthetic compounds showed antioxidant properties superior to the positive control barettin. Two of the prepared compounds displayed inhibitory activity similar to commercial antioxidants with significant inhibition at low µg/mL concentrations. The toxicity of the compounds was also investigated against MRC-5 lung fibroblasts and none of the included compounds displayed any toxicity at 50 µg/mL

Having children with multiple partners is associated with reduced risk of malignant melanoma: an observation seeking a plausible explanation

Anne V Olesen1,2,3, Erik T Parner4, Preben B Mortensen5, Cecilia H Ramlau-Hansen6, Jørn Olsen71Institute of Public Health, Department of Epidemiology, University of Aarhus; 2Unit for Psychiatric Research, Aalborg Psychiatric Hospital; 3Department of Clinical Epidemiology, Aarhus University Hospital; 4Institute of Public Health, Department of Biostatistics; 5National Centre for Register-based Research; 6Department of Occupational Medicine, Aarhus University Hospital, Denmark; 7Department of Epidemiology, School of Public Health, University of California, Los Angeles, USAObjective: We examined the association between the number of partners that mothers and fathers have children with and occurrence of cutaneous malignant melanoma (CMM).Methods: We conducted a complete registry-based follow-up of all Danish mothers born after 1935 from the birth of their second child until CMM, death, emigration, or end of study in 2002. We conducted a similar follow-up of the corresponding fathers. Incidence rate ratios (IRR) and confidence intervals (CI) were estimated by Poisson regression.Results: This study corroborates that women having children with three or more men are half as likely to have CMM as women who have children with one man: incidence rate ratio (IRR) = 0.51, 95% CI: 0.29, 0.91; having children by two fathers reduces risk among women by 20%: IRR = 0.80, 95% CI: 0.70, 0.91. Fathers with multiple partners tend to face a similar risk reduction.Conclusion: The similar patterns of mothers and fathers challenge us to consider and propose likely mechanisms common to both sexes. The patterns of reduced risk have now been reported in two large independent complete population-based studies in Sweden and Denmark.Keywords: malignant melanoma, epidemiology, children with multiple partner

Size-Dependence of the Wavefunction of Self-Assembled Quantum Dots

The radiative and non-radiative decay rates of InAs quantum dots are measured by controlling the local density of optical states near an interface. From time-resolved measurements we extract the oscillator strength and the quantum efficiency and their dependence on emission energy. From our results and a theoretical model we determine the striking dependence of the overlap of the electron and hole wavefunctions on the quantum dot size. We conclude that the optical quality is best for large quantum dots, which is important in order to optimally tailor quantum dot emitters for, e.g., quantum electrodynamics experiments.Comment: 5 pages, 3 figure

Quasi-one-dimensional intermittent flux behavior in superconducting films

Intermittent filamentary dynamics of the vortex matter in superconductors is found in films of YBa2Cu3O7-δ deposited on tilted substrates. Deposition of this material on such substrates creates parallel channels of easy flux penetration when a magnetic field is applied perpendicular to the film. As the applied field is gradually increased, magneto-optical imaging reveals that flux penetrates via numerous quasi-one-dimensional jumps. The distribution of flux avalanche sizes follows a power law, and data collapse is obtained by finite-size scaling, with the depth of the flux front used as crossover length. The intermittent behavior shows no threshold value in the applied field, in contrast to conventional flux jumping. The results strongly suggest that the quasi-one-dimensional flux jumps are of a different nature than the thermomagnetic dendritic (branching) avalanches that are commonly found in superconducting films