Regio- and diastereoselective condensation of resorcarenes with primary amines and formaldehyde

Abstract Mannich reactions of resorcarenes 1 with chiral amines yield single diastereomeric tetrakis-(benzodihydro-1,3-oxazine) derivatives 2 in high yields (80–90%). Epimerisation of these products occurs in the presence of acid.

Regioselective synthesis of calixcrowns derived from p-tert-butylcalix[5]arene

Abstract Alkylation of p-tert-butylcalix[5]arene with oligoethylene glycol-ditosylates in the presence of CsF affords the 1,3-bridged calix[5]crowns 1a–c in 51 to 72% yield. In the case of hexaethylene glycol the isomeric 1,2-bridged calix[5]crown-7 2c was obtained additionally. The calixcrowns were further modified by alkylation of the remaining hydroxyl groups.

Cation-π interactions between neutral calix[5]arene hosts and cationic organic guests

Abstract The binding properties of the 1,3-bridged calix[5]crowns 1–3 towards a number of quaternary ammonium, phosphonium, and iminium ions have been investigated by 1H NMR in CDCl3 solution, where the sole driving force for association is provided by cation-π interactions. We have found that the cavity of a calix[5]arene fixed in a cone-like conformation provides a fairly efficient, but rather unselective, receptor site for quaternary salts. The conformationally mobile p-tert-butylcalix[5]arene (4) is in general a much less efficient binder than the more preorganized calixcrowns, but displays a remarkable selectivity towards N-methylquinuclidinium ion that is believed to arise from a good…

ChemInform Abstract: Regioselective Synthesis of Calixcrowns Derived from p-tert-Butylcalix( 5)arene.