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N- functionalized aziridines, which are both useful intermediates and important synthetic targets, can be envisioned as arising from the addition of nitrenes ( i.e ., NR fragments) to olefinic substrates. The exceptional reactivity of most nitrenes, in particular with respect to unimolecular decomposition, prevents general application of nitrene-transfer to the synthesis of N -functionalized aziridines. Here we demonstrate N -aryl aziridine synthesis via 1) olefin aziridination with N -aminopyridinium reagents to afford N -pyridinium aziridines followed by 2) Ni-catalyzed C–N cross-coupling of the N -pyridinium aziridines with aryl boronic acids. The N -pyridinium aziridine intermediates also participate in ring-opening chemistry with a variety of nucleophiles to afford 1,2-aminofunctionalization products. Mechanistic investigations indicate aziridine cross-coupling proceeds via a noncanonical mechanism involving initial aziridine opening promoted by the bromide counterion of the Ni catalyst, C–N cross-coupling, and finally aziridine reclosure. Together, these results provide new opportunities to achieve selective incorporation of generic aryl nitrene equivalents in organic molecules. Aziridines are useful intermediates, present in important synthetic targets. Here, the authors show a strategy for the synthesis of N-aryl aziridines based on N-aminopyridinium reagents followed by Ni-catalyzed C–N cross-coupling of N-pyridinium aziridines with aryl boronic acids.

Arylamines are common structural motifs in pharmaceuticals, natural products, and materials precursors. While olefin aminofunctionalization chemistry can provide entry to arylamines, classical polar reactions typically afford Markovnikov products. Nitrogen-centered radical intermediates provide the opportunity to access anti-Markovnikov selectivity, however, anti-Markovnikov arylamination is unknown in large part due to lack of arylamine radical precursors. Here, we introduce bidirectional electron transfer processes to generate arylamine radical intermediates from N-pyridinium arylamines: Single-electron oxidation provides arylamine radicals that engage in anti-Markovnikov olefin aminopyridylation; single-electron reduction unveils arylamine radicals that engage in anti-Markovnikov olefin aminofunctionalization. Demonstration of both oxidative and reductive mechanisms to generate arylamine radicals from a common N-aminopyridinium precursor provides new methods to rapidly construct and diversify arylamine scaffolds from readily available radical precursors.

Kans grass ( Saccharum spontaneum ) is a weed species that is frequently found in many heavy metal-enriched waste dumps including fly ash pond sites. In this study, among a collection of phosphate-solubilizing bacterial strains isolated from the rhizosphere of Saccharum spontaneum present in the abandoned ash pond site of Mejia Thermal Power Station (MTPS-DVC), three strains were characterized for their plant growth-promoting abilities. The isolates identified as Bacillus anthracis strain MHR2, Staphylococcus sp. strain MHR3 and Bacillus sp. strain MHR4 had phosphate solubilization indices of 2.86, 2.31 and 2.40 and they produced soluble phosphates of 700, 600 and 640 mg l −1 , respectively, in 4 days. In all the PSBs, pH significantly decreased, indicating the production of various organic acids. They showed other plant growth-promoting features like production of ammonia, siderophore, hydrocyanide and IAA. All of them were resistant to multiple heavy metals and antibiotics. Dry and fresh weight and shoot and root lengths of Brassica juncea L. increased in the presence of these isolates in pot cultures. The strains also increased phytoextraction ability of plants by enhancing the metal accumulation in plant tissues. Thus, the isolated indigenous and stress-adapted rhizobacteria may serve as potential biotechnological tool for the successful ecorestoration of various metal-contaminated sites.

Fly ash (FA), the major by-product of coal-fired thermal power plants, causes significant environmental degradation owing to its injurious heavy metal contents. Leaching of arsenic (As) from ash ponds is especially significant as As released from FA can increase As concentration of drinking water above maximum contaminant level of 10 ppb. The aim of this paper was demonstration of As bioremediation potential of indigenous As resistant bacteria present in the weathered pond ash sample. Ten isolates belonging to Bacillus, Micrococcus, Kytococcus and Staphylococcus genera were characterized. Biochemical tests showed reduction of relatively non toxic arsenate to more toxic arsenite by two strains while four strains showed oxidation of arsenite to arsenate. Two exoplolysaccharide producing strains were shown to absorb As within their biomass. Total heterotrophs versus As resistant heterotrophs counting performed showed that FA was enriched with As resistant heterotrophs. Column leaching based microcosm study revealed overall As detoxification potential of the isolated microbes.

Eight chromium resistant bacteria were isolated from a dry fly ash sample of DVC-MTPS thermal power plant located in Bankura, West Bengal, India. These isolates displayed different degrees of chromate reduction under aerobic conditions. According to 16S rDNA gene analysis, five of them were Staphylococcus, two were Bacillus and one was Micrococcus. The minimum inhibitory concentration towards chromium and the ability to reduce hexavalent chromium to trivalent chromium was highest in Staphylococcus haemolyticus strain HMR17. All the strains were resistant to multiple heavy metals (As, Cu, Cd, Co, Zn, Mn, Pb and Fe) and reduced toxic hexavalent chromium to relatively non toxic trivalent chromium even in the presence of these multiple heavy metals. All of them showed resistance to different antibiotics. In a soil microcosm study, S. haemolyticus strain HMR17 completely reduced 4 mM hexavalent chromium within 7 days of incubation.