Generating alkyl carbanions for organic synthesis
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C(sp3)–heteroatom bond formation by iron-catalyzed soft couplings
Carbon–heteroatom bonds are of great importance due to their prevalence in pharmaceuticals, agrochemicals, materials, and natural products. Despite the effective use of metal-catalyzed cross-coupling reactions between sp2-hybridized organohalides and soft heteroatomic nucleophiles for carbon–heteroatom bond formation, the use of sp3-hybridized organohalides remain limited and the coupling with thiols remains elusive. Here, we report the coupling of sp3-hybridized benzyl or tertiary halides with soft thiol nucleophiles catalyzed by iron and extend the utility to alcohol and amine nucleophiles. The reaction is broad in substrate scope for both coupling partners and applicable in the construction of congested tri- and tetrasubstituted carbon centers as well as β-quaternary heteroatomic products. The synthetic utility is further emphasized by gram-scale synthesis and rapid herbicide library synthesis. Overall, we provide an efficient method to prepare pharmaceutically and materially relevant carbon–heteroatom bonds by expanding iron-catalyzed cross-coupling reactions to the coupling of sp3-hybridized organohalides with soft nucleophiles.
A robust organic hydrogen sensor for distributed monitoring applications
Hydrogen is an abundant and clean energy source that could help to decarbonize difficult-to-electrify economic sectors. However, its safe deployment relies on the availability of cost-effective hydrogen detection technologies. We describe a hydrogen sensor that uses an organic semiconductor as the active layer. It can operate over a wide temperature and humidity range. Ambient oxygen p-dopes the organic semiconductor, which improves hole transport, and the presence of hydrogen reverses this doping process, leading to a drop in current and enabling reliable and rapid hydrogen detection. The sensor exhibits a high responsivity (more than 10,000), fast response time (less than 1 s), low limit of detection (around 192 ppb) and low power consumption (less than 2 μW). It can operate continuously for more than 646 days in ambient air at room temperature. We show that the sensor outperforms a commercial hydrogen detector in realistic sensing scenarios, illustrating its suitability for application in distributed sensor networks for early warning of hydrogen leaks and preventing explosions or fires.
Chemical linkers switch triglycerol detergents from bacterial protein purification to mild antibiotic amplification
Non-ionic detergents enable the investigation of cell membranes, including biomolecule purification and drug delivery. The question of whether non-ionic detergents associated with satisfying protein yields following extraction and affinity purification of proteins from lysed E. coli membranes can amplify antibiotics on whole-cell E. coli remains to be addressed. We unlock the modular chemistry of linear triglycerol detergents to reveal that more polar, non-ionic detergents that form globular micelles work better in amplifying antimicrobial activities of antibiotics than in purifying the membrane proteins mechanosensitive channel and aquaporin Z. Less polar detergents that form worm-like micelles indicate poor performances in both applications. With chromatography we demonstrate how fine-tuning the polarity of chemical linkers between detergent headgroups and tails can switch the utility of detergents from protein purification to antibiotic amplification. We anticipate our findings to be a starting point for structure-property studies to better understand detergent designs in supramolecular chemistry and membrane research.
Flash Joule heating for synthesis, upcycling and remediation
Electric heating methods are being developed and used to electrify industrial applications and lower their carbon emissions. Direct Joule resistive heating is an energy-efficient electric heating technique that has been widely tested at the bench scale and could replace some energy-intensive and carbon-intensive processes. In this Review, we discuss the use of flash Joule heating (FJH) in processes that are traditionally energy-intensive or carbon-intensive. FJH uses pulse current discharge to rapidly heat materials directly to a desired temperature; it has high-temperature capabilities (>3,000 °C), fast heating and cooling rates (>102 °C s−1), short duration (milliseconds to seconds) and high energy efficiency (~100%). Carbon materials and metastable inorganic materials can be synthesized using FJH from virgin materials and waste feedstocks. FJH is also applied in resource recovery (such as from e-waste) and waste upcycling. An emerging application is in environmental remediation, where FJH can be used to rapidly degrade perfluoroalkyl and polyfluoroalkyl substances and to remove or immobilize heavy metals in soil and solid wastes. Life-cycle and technoeconomic analyses suggest that FJH can reduce energy consumption and carbon emissions and be cost-efficient compared with existing methods. Bringing FJH to industrially relevant scales requires further equipment and engineering development.
Pilot-scale partial nitrification and anaerobic ammonium oxidation system for nitrogen removal from municipal wastewater
Partial nitrification has the advantages of saving energy and reducing the need for carbon sources in municipal wastewater treatment. However, for municipal wastewater with low ammonia, start-up and maintenance of partial nitrification is a worldwide challenge. Here we developed a pilot-scale double sludge system consisting of two sequencing batch reactors for partial nitrification (12 m2) and denitrification/anaerobic ammonium oxidation (denitrification/anammox, 8.4 m2) to treat municipal wastewater. Partial nitrification was maintained at no ammonium remaining with a nitrite accumulation rate of 87.7%. This study found that partial nitrification system effluent chemical oxygen demand increased from 24.8 mg L−1 to 64.9 mg L−1 accompanied by transformation from complete nitrification to partial nitrification. In the denitrification/anammox system, the reduction of nitrite to nitrogen required about 40% less carbon consumption than nitrate. High nitrogen removal was achieved with effluent total inorganic nitrogen of 2.7 mg L−1 without carbon addition. This work provided a pilot-scale demonstration of low-carbon high-nitrogen removal.
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