Chiral Amphiphilic Secondary Amine-Porphyrin Hybrids for Aqueous Organocatalysis

Molecules

Joaquim Crusats¹  Pol Torres¹  Albert Moyano¹  Aitor Arlegui¹  Victor Cuesta¹ 

[1] Section of Organic Chemistry, Department of Inorganic and Organic Chemistry, University of Barcelona, Faculty of Chemistry, C. de Martí i Franquès 1-11, 08028 Barcelona, Spain;

关键词: J-aggregates;    aqueous organocatalysis;    porphyrins;    switchable catalysis;    aldol reaction;    Michael reaction;   

DOI  :  10.3390/molecules25153420

来源: DOAJ

【 摘 要 】

Two chiral proline-derived amphiphilic 5-substituted-10,15,20-tris(4-sulfonatophenyl)porphyrins were prepared, and their pH-dependent supramolecular behavior was studied. In neutral aqueous solutions, the free-base form of the hybrids is highly soluble, allowing enamine-based organocatalysis to take place, whereas under acidic conditions, the porphyrinic protonated core of the hybrid leads to the formation of self-assembled structures, so that the hybrids flocculate and their catalytic activity is fully suppressed. The low degree of chirality transfer observed for aqueous Michael and aldol reactions strongly suggests that these reactions take place under true “in water” organocatalytic conditions. The highly insoluble catalyst aggregates can easily be separated from the reaction products by centrifugation of the acidic reaction mixtures, and after neutralization and desalting, the sodium salts of the sulfonated amine-porphyrin hybrids, retaining their full catalytic activity, can be recovered in high yield.

【 授权许可】

Unknown