Insights into the synthesis of pillararene and its conversion into pillararene
M. Da Pian, C. A. Schalley, F. Fabris, A. Scarso – 2019
The synthesis of pillararenes from p -dialkoxybenzene and formaldehyde in the presence of iron(III) chloride and tetramethylammonium chloride under mild reaction conditions was investigated in detail. For the ﬁ rst time, the presence of linear intermediate oligomers and their conversion into pillararenes was demonstrated. Incorporation experiments were carried out using methoxy- and ethoxy-functionalized pillararenes that were reacted respectively with 1,4-diethoxy- and 1,4-dimethoxybenzene, observing the formation of the corresponding co-pillararene derivatives, PMeEt and PEtMe. An experiment in which methoxy- and ethoxy-functionalized pillararenes were reacted together led to the major formation of scrambled P derivatives characterized by a bell shape distribution of ethoxy and methoxy aromatic units. Co-Pillararenes P were also detected by ESI-MS in minor amounts with a similar symmetrical distribution of substituents that allowed the proposal of multiple cleavage events occurring on the same macrocyclic ring forming in solution a series of smaller fragments, whose recombination leads to the observed product distribution of P and P derivatives.