A Facile and Efficient Preparation of Pillararenes and a Pillarquinone

Abstract

Ring around the roses: The ipso substitution of benzene rings makes a simple and efficient synthesis of pillar[n]arenes (n=5, 6) possible. Pillar[6]arenes (see picture) and pillar[5]quinone, an oxidation product of pillar[5]arene, are novel, highly promising host systems for host–guest chemistry.

New Synthetic Host Pillararenes: Their Synthesis and Application to Supramolecular Materials

“…By using 3 equiv of paraformaldehyde to 1,4-dimethoxybenzene, 1 was successfully isolated in high yield (71%). 25 Lewis acid or organic acid-catalyzed synthesis of pillar [5]arenes using different monomers such 2,5-alkoxybenzyl bromides (path II), 26,27 2,5-alkoxybenzyl alcohols (path III), 27 and 2,5-bis(alkoxymethyl)-1,4-diethoxybenzene (path IV) 28,29 were reported by the Nierengarten, Huang, and Meier research groups. The mechanism for the cyclization is presumed to be a FriedelCrafts alkylation from their studies.…”

“…This is due to the easy synthesis of various dialkoxybenzene monomers. Cyclization of dialkoxybenzene derivatives afforded various pillar [5]arene derivatives such as a series of peralkyl-18 27,28,30 and branched alkyl-substituted pillar [5]arenes 911.…”

Water-Soluble Pillar[5]arenes: Synthesis and Characterization of the Inclusion Complexes with p-Toluenesulfonic Acid

“…Earlier it was shown catalytic amounts of p-toluenesulfonic acid led to oligomerization of monomers (2,5-bis(benzyloxymethyl)-1,4-diethoxybenzene) delivering the cyclic pentamer 1. [16] Therefore we can propose p-toluenesulfonic acid is the template in synthesis pillar [5]arenes.…”

Functionalization reactions of calixarenes

“…Calixarenes are receptors for neutral and charged species, [18][19][20] they form complexes with metal ions, [21][22][23] and are promising for environment protection due to their ability to extract Related to calixarenes also are the calixcrowns, 53,54 which are calixarenes bearing crown ether units; calixquinones, 55,56 containing one or two quinone units instead of phenol moieties of calixarenes; calixpyrroles, [57][58][59] built from pyrrole units, and calixphyrins, 60,61 formed by the reduction of porphyrins. Pillarenes, [62][63][64] in which benzene rings are linked by para, and not by meta positions as in calixarenes should also be included. A special group are the thia, oxa and azacalixarenes, in which the linking methylene groups of calixarenes are formally replaced by sulfur, [65][66][67] oxygen, [68][69][70] or nitrogen, [71][72][73] atoms, respectively.…”