Covalent capture of oriented calix[6] arene rotaxanes by a metal-free active template approach

We describe the active template effect of a calix[ 6] arene host towards the alkylation of a complexed pyridylpyridinium guest. The acceleration of the reaction within the cavity is significant and rim-selective, enabling the efficient preparation of rotaxanes with full control of the mutual orientation of their nonsymmetric components.