A common problem encountered in enantioselective organocatalysis is the aggregation of the catalyst, which can result in a relevant decrease of the efficiency and selectivity of the process. In the asymmetric synthesis of chiral benzofuranones, recently reported by us, we noted a remarkable increase of the reaction yield upon the addition of one of the reagents in a portionwise manner rather than in a single addition. We investigated this phenomenon by several experimental techniques such as 1D and 2D NMR experiments, UV-Vis spectroscopy, circular dichroism and dynamic light scattering. In addition, we studied the kinetic profile of this reaction using a simple numerical model and carried out in silico investigations. All these different approaches point to the conclusion that in the reaction medium a supramolecular polymerization/aggregation phenomenon, based on weak interactions, occurs and such a process is promoted by a quinone, which is one of the reagents of the benzofuranone synthesis. The portionwise mode of addition is a known strategy which can improve the performance of many synthetic procedures and this strategy is commonly adopted on account of empirical experience. However, our results provide an explanation, based on a chemical kinetic model, of the reason why the portionwise addition affects in such a dramatic way the yield of the benzofuranone synthesis catalyzed by Cinchona alkaloids.
Organocatalysis and catalyst aggregation: a study using the asymmetric synthesis of benzofuranones as a test reaction / Salvio, Riccardo; Massaro, Luca; Puglisi, Antonio; Angelini, Lucrezia; Antenucci, Achille; Placidi, Simone; Sciubba, Fabio; Galantini, Luciano; Bella, Marco. - In: ORGANIC & BIOMOLECULAR CHEMISTRY. - ISSN 1477-0520. - STAMPA. - 16:38(2018), pp. 7041-7049. [10.1039/c8ob01772g]
Organocatalysis and catalyst aggregation: a study using the asymmetric synthesis of benzofuranones as a test reaction
Riccardo Salvio
Primo
Supervision
;Antonio PuglisiMembro del Collaboration Group
;Achille AntenucciMembro del Collaboration Group
;Simone PlacidiMembro del Collaboration Group
;Fabio SciubbaMembro del Collaboration Group
;Luciano GalantiniMembro del Collaboration Group
;Marco Bella
Ultimo
Supervision
2018
Abstract
A common problem encountered in enantioselective organocatalysis is the aggregation of the catalyst, which can result in a relevant decrease of the efficiency and selectivity of the process. In the asymmetric synthesis of chiral benzofuranones, recently reported by us, we noted a remarkable increase of the reaction yield upon the addition of one of the reagents in a portionwise manner rather than in a single addition. We investigated this phenomenon by several experimental techniques such as 1D and 2D NMR experiments, UV-Vis spectroscopy, circular dichroism and dynamic light scattering. In addition, we studied the kinetic profile of this reaction using a simple numerical model and carried out in silico investigations. All these different approaches point to the conclusion that in the reaction medium a supramolecular polymerization/aggregation phenomenon, based on weak interactions, occurs and such a process is promoted by a quinone, which is one of the reagents of the benzofuranone synthesis. The portionwise mode of addition is a known strategy which can improve the performance of many synthetic procedures and this strategy is commonly adopted on account of empirical experience. However, our results provide an explanation, based on a chemical kinetic model, of the reason why the portionwise addition affects in such a dramatic way the yield of the benzofuranone synthesis catalyzed by Cinchona alkaloids.File | Dimensione | Formato | |
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