Synthesis of Functional meso-Aryl Porphomonomethenes and Porphodimethenes:  Application to the Preparation of a Chiral Calix[4]phyrin Dimer

Reaction of 5,5-dimethyldipyrromethane (1) with electron-deficient aryl aldehydes in the presence of BF₃−Et₂O and NH₄Cl in propionitrile constitutes efficient, easy access to unprecedented, functional porphomonomethenes together with the expected porphodimethenes (calix[4]phyrins). Alternatively, when the reaction was carried out in CH₂Cl₂ in the presence of an acid and Florisil, the expected bis-arylcalix[4]phyrin was isolated in 41% yield, while no scrambled macrocycle was detected. After reduction of the nitro function, porphomonomethene 9 was efficiently condensed with the binaphthyl diacyl chloride (10) leading to the first chiral calix[4]phyrin dimer (11) that exhibits a moderate enantiorecognition toward the enantiomers of malic acid.