Stepwise, Protecting Group Free Synthesis of [4]Rotaxanes.

Despite significant advances in the last three decades towards high yielding syntheses of rotaxanes, the preparation of systems constructed from more than two components remains a challenge. Herein we build upon our previous report of an active template copper-catalyzed azide-alkyne cycloaddition (CuAAC) rotaxane synthesis with a diyne in which, following the formation of the first mechanical bond, the steric bulk of the macrocycle tempers the reactivity of the second alkyne unit. We have now extended this approach to the use of 1,3,5-triethynylbenzene in order to successively prepare [2]-, [3]- and [4]rotaxanes without the need for protecting group chemistry.

Iterative Synthesis of Oligo[n]rotaxanes in Excellent Yield.

We present an operationally simple iterative coupling strategy for the synthesis of oligomeric homo- and hetero[n]rotaxanes with precise control over the position of each macrocycle. The exceptional yield of the AT-CuAAC reaction, combined with optimized conditions that allow the rapid synthesis of the target oligomers, opens the door to the study of precision-engineered oligomeric interlocked molecules.

Synthesis of a rotaxane Cu(I) triazolide under aqueous conditions.

We describe the serendipitous isolation of a stable, neutral, monomeric mechanically interlocked Cu(I) triazolide under aqueous conditions. This "trapped" intermediate of the CuAAC catalytic cycle is sterically protected from reprotonation by the rotaxane architecture, which renders the Cu(I)-C bond stable toward moisture and air--even carboxylic acids protonate the Cu(I)-C bond only slowly. The isolation of this remarkably stable Cu(I) organometallic points toward potential applications of mechanical bonding in the study of reactive intermediates.

Studies on transannulation reactions across a nine-membered ring: the synthesis of natural product-like structures.

A series of diverse natural product-like structures have been synthesised by the use of a number of novel transannulation reactions across a cyclononene ring. Transannular cyclisations through oxygen functionality have generated a number of bicyclo[5.3.