Attempted [2]Catenane Synthesis via a Quasi[1]catenane by a Templated Backfolding Strategy

A templated backfolding concept to construct a [2]catenane was attempted via a quasi[1]catenane showing an inverted spiro geometry. The template is covalently connected to the ketal‐connected semi‐perpendicular‐arranged linear precursors and spatially directs the sterically congested backfolding macrocyclizations that are required to give a quasi[1]catenane. So far, we are unable to hydrolyze the cyclic ketal to liberate the [2]catenane. A tartaric acid derived ketal‐centered quasi[1]catenane is prepared by a template‐directed covalent strategy forcing backfolding macrocyclizations. All key steps towards the quasi[1]catenane, i.e., macrolactonization, CuAAC macrocyclizations and RCM towards a cycloolefin, worked well. Unfortunately, all attempts to hydrolyze the ketal liberating the [2]catenane architecture failed.