Morpholines are prevalent in medicinal chemistry due to their favorable pharmacokinetic properties and widespread presence in FDA-approved drugs. Existing methods for morpholine synthesis often require prefunctionalized or protected reagents, limiting their versatility and efficiency. Here, we present a photocatalytic, diastereoselective annulation strategy for the synthesis of morpholines directly from readily available starting materials. This method employs a visible-light-activated photocatalyst, Lewis acid, and Brønsted acid to achieve high yields and stereoselectivity. It also provides access to diverse substitution patterns, including challenging tri- and tetra-substituted morpholines. Mechanistic studies reveal that the reaction proceeds through the formation of a radical cation intermediate, with triflic acid playing critical roles in protonating the substrate, preserving the photocatalyst, and preventing product oxidation. Beyond morpholines, this strategy is extended to piperidines, pyrrolidines, and other privileged nitrogen heterocycles. Our findings provide a modular approach for constructing complex, medicinally valuable scaffolds, advancing both synthetic and medicinal chemistry.

Open metal sites (OMSs) represent a distinctive feature of metal-organic frameworks (MOFs), intertwined with guest accommodation and energy transfer within nanosized pores. Fine-tuning OMSs provide an effective approach to regulating MOF’s responsiveness and binding affinity towards guests, allowing for the construction of luminescent sensors for specific analytes. Such a strategy remains unexplored due to the inherent complexity of the systems and sensing mechanisms. Herein, we delicately regulated the OMSs in PCN-700 through multiple synthetic methodologies, including direct synthesis, linker installation, and linker exchange. The resultant MOFs consist of Zr6-clusters featuring various coordination numbers. Notably, PCN-700-8u with unsaturated 8-coordinated Zr-clusters exhibited the highest sensitivity in detecting a toxic pesticide pentachloronitrobenzene (PCNB) due to the presence of strong coordination interaction, as validated through single crystal X-ray diffraction directly. PCN-700-10u/12u bearing unsaturated 10/12-coordinated clusters perform lower quenching efficiencies than PCN-700-8u, but higher than PCN-700-12s with saturated clusters. In contrast, all these MOFs exhibit similar quenching efficiencies towards hexachlorobenzene for the absence of coordination interaction. This study not only develops a cost-effective and easily attainable material for PCNB detection, but also illuminates the pivotal importance of OMSs in customizing MOF-based sensors for practical applications.

Particle exchange heat engines are a novel class of cyclic heat engines that are all-electrical, contain no moving parts and can therefore be scaled down to nanometer size. At the center of their operation is the manipulation of a particle flow between a hot and a cold reservoir through energy filtering mechanisms, where their efficiency depends primarily on the sharpness of the energy filter. In this study, we investigate the efficiency enhancement of such engines by utilizing ultra-sharp transmission resonances formed by magnetic impurities interacting with superconductors, known as Yu-Shiba-Rusinov bound states. To this end, we couple a neutral and stable diradical molecule to superconducting break-junction electrodes, and study its thermoelectric properties at ultra-low temperatures. By driving the molecular heat engine through a phase transition from a Kondo state into the Yu-Shiba-Rusinov regime, we observe a five fold increase in the thermoelectric power factor. This observation could pave the way for practical applications such as cryogenic waste heat recovery and efficient spot-cooling for future quantum computing architectures.

Trifluoromethylation is a key transformation in drug and agrochemical synthesis, yet current reagents often suffer from high cost, low atom economy, and low scalability. [Discover more...]