The formation of catenanes. The Mobius strip approach revisited

The ''Mobius strip approach'' for the synthesis of catenanes requires that a ladder shaped molecule (doubly functionalized at both ends) twists twice prior to bimacrocyclization. A successful application of this strategy was claimed in the 1960's. However, the catenanes were believed to be formed via a Mobius strip mechanism since, at that time, a metal coordinated all carbon cyclobutane was assumed to be an intermediate in the olefin metathesis. Although the incompatibility of the Mobius strip mechanism and the (later proposed) actual metathesis mechanism has been pointed out, the original claim keeps being cited as a successful one even in the recent literature. In this paper, the background of this mechanistic misconception is discussed, and it is demonstrated that the formation of catenanes in olefin metathesis is resulting from a statistical threading process.