Benzylic Oxidation of Pillar[5]Arene: From Homo‐ to Cross‐Conjugated Macrocyclic Systems
Jorge Juan Marco‐Guimbao, Eric Meichsner, Unai Calvo, Michel Holler, Béatrice Delavaux‐Nicot, Jon M. Matxain, Juan Luis Delgado, Jean‐François Nierengarten, Iwona NierengartenABSTRACT
Selective benzylic oxidations of pillar[5]arene have been carried out to generate all the possible oxidized derivatives containing from one up to five carbonyl subunits. By using a mild oxidizing agent, namely DDQ, the conditions have been optimized to preferentially generate the monoketone derivative. The corresponding polyketones have been obtained by oxidation of the pillar[5]arene with SeO 2 under microwave irradiation. Six out of the seven oxidation products have been characterized by x‐ray crystal structure analysis. Effects resulting from the homo‐ and the cross‐conjugation within this series of compounds have been investigated and analyzed with the help of DFT calculations. Finally, binding studies have been also carried out with the pillar[5]arene and the pentaketone derivative in order to evaluate the effect of the C═O subunits on the affinity of the macrocyclic system for guest molecules.