Enantioenriched tertiary alkyl halides are prevalent in bioactive molecules and can serve as versatile synthetic intermediates to construct complex structures. While conventional access to these motifs often hinges on stereoselective carbon− halogen or carbon−carbon bond formation reactions, desymmetric approaches using halogenated and prochiral tetrasubstituted carbons are largely elusive in comparison. Here, we report that a suite of dinuclear zinc catalysts with a prolinol-or pipecolinolderived tetradentate ligand can reductively desymmetrize a large collection of easily available halomalonic esters to α-halo-βhydroxyesters. These polyfunctionalized tertiary alkyl fluorides, chlorides, and bromides proved to be useful intermediates toward fluorinated drug analogs and polyhalogenated monoterpenes. The facile intramolecular epoxidation of the chiral chloride and bromide products has also enabled expeditious access to natural products containing tertiary alcohol motifs.
s. Since the current substation robot inspection process exists in the high-voltage switchgear status recognition is highly susceptible to the influence of complex environments such as low image contrast, light clutter interference, and blurred reading status details, this paper proposes an image enhancement and deep learning based substation switchgear state recognition method. A multi-scale Retinex-based image enhancement is proposed to enhance the adaptability of outdoor switchgear images to light changes; improve the YOLOx target detection network to introduces a lightweight ECA attention mechanism without dimensionality reduction based on the original YOLOx model’s backbone network CSPDarknet, allowing the model to learn classification features while also focusing on learning spatial features. The experimental results show that the improved network can accurately identify the boundary information of anomalies, and the quality of its prediction results will not be reduced for noise-containing data, and the network shows strong generalization, robustness, accuracy and rapidity, providing certain conditions for realizing substation equipment condition monitoring.
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