Chiral Amphiphilic Secondary Amine-Porphyrin Hybrids for Aqueous Organocatalysis.

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.

Spontaneous mirror-symmetry breaking coupled to top-bottom chirality transfer: from porphyrin self-assembly to scalemic Diels-Alder adducts.

This report shows how the net supramolecular chirality that emerged by spontaneous mirror-symmetry breaking (SMSB) at the mesoscale level can be transferred towards asymmetric solution chemistry. The J-aggregates obtained by self-assembly of an achiral porphyrin act as chiral counteranions in an iminium-promoted Diels-Alder reaction, leading to enantiomeric imbalances in the final adducts.

5-Phenyl-10,15,20-Tris(4-sulfonatophenyl)porphyrin: Synthesis, Catalysis, and Structural Studies.

A convenient protocol for the preparation of 5-phenyl-10,15,20-tris(4-sulfonatophenyl)porphyrin, a water-soluble porphyrin with unique aggregation properties, is described. The procedure relies on the one-pot reductive deamination of 5-(4-aminophenyl)-10,15,20-tris(4-sulfonatophenyl)porphyrin, that can be in turn easily obtained from 5,10,15,20-tetraphenylporphyrin by a known three-step sequence involving mononitration, nitro to amine reduction and sulfonation of the phenyl groups. This method provides the title porphyrin in gram scale, and compares very favorably with the up to now only described procedure based on the partial sulfonation of TPP, that involves a long and tedious chromatographic enrichment of the final compound.