Transition metal catalysis benefitting from supramolecular interactions in the secondary coordination sphere in order to pre-organize substrates around the active site and reach a specific selectivity typically occurs under long reaction times and mild reaction temperatures with the aim to maximize such subtle effects. Herein, we demonstrate that the kinetically labile Zn⋯N interaction between a pyridine substrate and a zinc–porphyrin site serving for substrate binding is a unique type of weak interaction that enables identification of supramolecular effects in transition metal catalysis after one hour at a high reaction temperature of 130 °C. Under carefully selected reaction conditions, supramolecularly-regulated palladium-catalyzed Mizoroki–Heck reactions between 3-bromopyridine and terminal olefins (acrylates or styrenes) proceeded in a more efficient manner compared to the non-supramolecular version. The supramolecular catalysis developed here also displayed interesting substrate-selectivity patterns.
{"title":"Boosting the activity of Mizoroki–Heck cross-coupling reactions with a supramolecular palladium catalyst favouring remote Zn⋯pyridine interactions†","authors":"Naba Abuhafez and Rafael Gramage-Doria","doi":"10.1039/D2FD00165A","DOIUrl":"https://doi.org/10.1039/D2FD00165A","url":null,"abstract":"<p >Transition metal catalysis benefitting from supramolecular interactions in the secondary coordination sphere in order to pre-organize substrates around the active site and reach a specific selectivity typically occurs under long reaction times and mild reaction temperatures with the aim to maximize such subtle effects. Herein, we demonstrate that the kinetically labile Zn⋯N interaction between a pyridine substrate and a zinc–porphyrin site serving for substrate binding is a unique type of weak interaction that enables identification of supramolecular effects in transition metal catalysis after one hour at a high reaction temperature of 130 °C. Under carefully selected reaction conditions, supramolecularly-regulated palladium-catalyzed Mizoroki–Heck reactions between 3-bromopyridine and terminal olefins (acrylates or styrenes) proceeded in a more efficient manner compared to the non-supramolecular version. The supramolecular catalysis developed here also displayed interesting substrate-selectivity patterns.</p>","PeriodicalId":76,"journal":{"name":"Faraday Discussions","volume":"244 ","pages":" 186-198"},"PeriodicalIF":3.4,"publicationDate":"2023-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://pubs.rsc.org/en/content/articlepdf/2023/fd/d2fd00165a?page=search","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"3693584","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Arnau Vicens, Laia Vicens, Giorgio Olivo, Osvaldo Lanzalunga, Stefano Di Stefano and Miquel Costas
Site-selective oxidation of aliphatic C–H bonds is a powerful synthetic tool because it enables rapid build-up of product complexity and diversity from simple precursors. Besides the poor reactivity of alkyl C–H bonds, the main challenge in this reaction consists in differentiating between the multiple similar sites present in most organic molecules. Herein, a manganese oxidation catalyst equipped with two 18-benzo-6-crown ether receptors has been employed in the oxidation of the long chain tetradecane-1,14-diamine. 1H-NMR studies evidence simultaneous binding of the two protonated amine moieties to the crown ether receptors. This recognition has been used to pursue site-selective oxidation of a methylenic site, using hydrogen peroxide as oxidant in the presence of carboxylic acids as co-ligands. Excellent site-selectivity towards the central methylenic sites (C6 and C7) is observed, overcoming selectivity parameters derived from polar deactivation by simple amine protonation and selectivity observed in the oxidation of related monoprotonated amines.
{"title":"Site-selective methylene C–H oxidation of an alkyl diamine enabled by supramolecular recognition using a bioinspired manganese catalyst†","authors":"Arnau Vicens, Laia Vicens, Giorgio Olivo, Osvaldo Lanzalunga, Stefano Di Stefano and Miquel Costas","doi":"10.1039/D2FD00177B","DOIUrl":"https://doi.org/10.1039/D2FD00177B","url":null,"abstract":"<p >Site-selective oxidation of aliphatic C–H bonds is a powerful synthetic tool because it enables rapid build-up of product complexity and diversity from simple precursors. Besides the poor reactivity of alkyl C–H bonds, the main challenge in this reaction consists in differentiating between the multiple similar sites present in most organic molecules. Herein, a manganese oxidation catalyst equipped with two 18-benzo-6-crown ether receptors has been employed in the oxidation of the long chain tetradecane-1,14-diamine. <small><sup>1</sup></small>H-NMR studies evidence simultaneous binding of the two protonated amine moieties to the crown ether receptors. This recognition has been used to pursue site-selective oxidation of a methylenic site, using hydrogen peroxide as oxidant in the presence of carboxylic acids as co-ligands. Excellent site-selectivity towards the central methylenic sites (C6 and C7) is observed, overcoming selectivity parameters derived from polar deactivation by simple amine protonation and selectivity observed in the oxidation of related monoprotonated amines.</p>","PeriodicalId":76,"journal":{"name":"Faraday Discussions","volume":"244 ","pages":" 51-61"},"PeriodicalIF":3.4,"publicationDate":"2023-01-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://pubs.rsc.org/en/content/articlepdf/2023/fd/d2fd00177b?page=search","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"3936058","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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