Resorcin[4]arene‐Based Molecular Baskets and Water‐Soluble Container Molecules: Synthesis and 1 H NMR Host–Guest Complexation Studies

• Published in: European journal of organic chemistry Vol. 2014; no. 17; pp. 3575 - 3583
• Main Authors: Fankhauser, Daniel, Kolarski, Dušan, Grüning, Wolfram R., Diederich, François
• Format: Journal Article
• Language: English
• Published: 01.06.2014
• ISSN: 1434-193X; 1099-0690
• DOI: 10.1002/ejoc.201402140

Resorcin[4]arene‐based molecular baskets, with four free or methylene‐bridged HO groups, and water‐soluble container molecules bearing poly(ethylene glycol) chains of different lengths on the lower rim and cap have been synthesized. These cavitands, topped with p ‐xylylene bridges, feature well‐defined cavities capable of encapsulating heteroalicyclic guests. Association constants ( K a ) were determined by 1 H NMR spectroscopy for the organic‐soluble molecular baskets in CDCl 3 and for the water‐soluble container molecules in D 2 O/CD 3 CN (2:1). Opposite guest selectivities were observed in the two environments. Upon complexation, the water‐soluble hosts show changes in their 1 H NMR spectra. In the absence of guests, the p ‐xylylene bridge rotates rapidly on the 1 H NMR timescale, revealing a time‐averaged achiral C 2 v structure, whereas this rotation is hindered by guest inclusion, resulting in spectra showing a racemic C 2 ‐symmetric host, indicative of planar chirality.