Synthesis of a chiral, water soluble porphyrin containing a pyrrolidine unit and initial study of its catalytic activity

Asymmetric organocatalysis have taken hold in the last decades due to affordability and lack of toxicity of their catalysts. Unfortunately, organocatalytic enantioselective reactions in an environmentally friendly and safe solvent as water are still scarce. During the training internship our aim has been to find an effective water soluble organocatalyst able to drive in an enantioselective fashion a reaction, to maximize the diasteromeric and the enantiomeric excess. Pursuing this objective we synthesized a meso 3-sulfonatophenyl porphyrin with a chiral aminoaldehyde substituent, with the sulfonate-groups allowing its solubilization in water and the chiral group which should improve the enantioselectivity. The chiral aldehyde has been prepared starting from L-proline, a widely used organocatalyst, and finally tried in an aldol reaction, giving excellent yield, moderate diastereoselectivity and very low enantiomeric excess. The reaction products can be easily removed washing in organic solvent and the catalyst can be recovered by aggregation in acidic medium.