Copper(i)-induced amplification of a [2]catenane in a virtual dynamic library of macrocyclic alkenes

Abstract

Olefin cross-metathesis of diluted dichloromethane solutions (≤0.15 M) of the 28-membered macrocyclic alkene C₁, featuring a 1,10-phenanthroline moiety in the backbone, as well as of catenand 1, composed of two identical interlocked C₁ units, generates families of noninterlocked oligomers C_i. The composition of the libraries is strongly dependent on the monomer concentration, but independent of whether C₁ or 1 is used as feedstock, as expected for truly equilibrated systems. Accordingly, the limiting value 0.022 M approached by the equilibrium concentration of C₁ when the total monomer concentration approaches the critical value, as predicted by the Jacobson–Stockmayer theory, provides a reliable estimate of the thermodynamically effective molarity. Catenand 1 behaves as a virtual component of the dynamic libraries, in that there is no detectable trace of its presence in the equilibrated mixtures, but becomes the major component – in the form of its copper(I) complex – when olefin cross-metathesis is carried out in the presence of a copper(I) salt.