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) twi sts twice prior to bimacrocyclization. A successful application of thi s strategy was claimed in the 1960's. However, the catenanes were beli eved to be formed via a Mobius strip mechanism since, at that time, a metal coordinated all carbon cyclobutane was assumed to be an intermed iate in the olefin metathesis. Although the incompatibility of the Mob ius strip mechanism and the (later proposed) actual metathesis mechani sm has been pointed out, the original claim keeps being cited as a suc cessful one even in the recent literature. In this paper, the backgrou nd of this mechanistic misconception is discussed, and it is demonstra ted that the formation of catenanes in olefin metathesis is resulting from a statistical threading process.