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  1. Abstract

    A simple experimental procedure for scaling carbene Brønsted basicity is described. The results highlight the strong basicity of pyrazol‐4‐ylidenes, a type of mesoionic carbene, also named cyclic‐bentallenes (CBA). They are more basic (pKaH>42.7 in acetonitrile) than the popular proazaphosphatrane Verkade bases, and even the Schwesinger phosphazene superbase P4(tBu). The basicity of these compounds can readily be tuned, and they are accessible in multigram quantities. These results open new avenues for carbon centered superbases.

     
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  2. Abstract

    Cyclic (Alkyl)(Amino)Carbenes (CAACs) have become forceful ligands for gold due to their ability to form very strong ligand‐metal bonds. Inspired by the success of Auranofin and other gold complexes as antitumor agents, we have studied the cytotoxicity of bis‐ and mono‐CAAC‐gold complexes on different cancer cell lines: HeLa (cervical cancer), A549 (lung cancer), HT1080 (fibrosarcoma) and Caov‐3 (ovarian cancer). Further investigations aimed at elucidating their mechanism of action are described. This includes quantification of affinities for TrxR, evaluation of their bioavailability and determination of associated cell death process. Moreover, Transmission Electron Microscopy (TEM) was used to study morphological changes upon exposure. Noticeably, a significant reduction in non‐specific binding to serum proteins was observed with CAAC complexes when compared to Auranofin. These results confirm the potential of CAAC‐gold complexes in biological environments, which may result in more specific drug‐target interactions and decreased side effects.

     
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  3. An air-stable (amino)(amido)radical was synthesized by reacting a cyclic (alkyl)(amino)carbene with carbazoyl chloride, followed by one-electron reduction. We show that an adjacent radical center weakens the amide bond. It enables the amino group to act as a strong acceptor under steric contraint, thus enhancing the stabilizing capto-dative effect. 
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  4. A novel family of cyclic (alkyl)(amino)carbenes, which we name cyclic (amino)(barrelene)carbenes (CABCs) is reported. The key synthetic step involves an intramolecular [4+2] cyclization of an anthracene derivative with an alkyne. This synthetic approach allows for the attachment of both aryl and alkyl groups on the nitrogen atom. When used as ligand, two of the barrelene hydrogens are in close contact with the metal, which could stabilize low valent catalytic intermediates. 
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