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Issue 38, 2018
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Organocatalysis and catalyst aggregation: a study using the asymmetric synthesis of benzofuranones as a test reaction

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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.

Graphical abstract: Organocatalysis and catalyst aggregation: a study using the asymmetric synthesis of benzofuranones as a test reaction

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Publication details

The article was received on 23 Jul 2018, accepted on 11 Sep 2018 and first published on 12 Sep 2018


Article type: Paper
DOI: 10.1039/C8OB01772G
Citation: Org. Biomol. Chem., 2018,16, 7041-7049
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    Organocatalysis and catalyst aggregation: a study using the asymmetric synthesis of benzofuranones as a test reaction

    R. Salvio, L. Massaro, A. Puglisi, L. Angelini, A. Antenucci, S. Placidi, F. Sciubba, L. Galantini and M. Bella, Org. Biomol. Chem., 2018, 16, 7041
    DOI: 10.1039/C8OB01772G

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