Rational Synthesis of Multicyclic Bis[2]catenanes

Abstract

Bis‐loop tetraurea calix[4]arene 6 has been prepared by acylation of the wide‐rim calix[4]arene tetraamine 1 with the activated bis(urethane) 8 under dilution conditions. Similarly the bis(Boc‐protected) tetraamine 2 is converted into the mono‐loop derivative 3 which after deprotection and acylation gives the bisalkenyl derivative 5. In apolar solvents this tetraurea calix[4]arene 5 forms regioselectively a single hydrogen‐bonded homodimer, from which the bis[2]catenane 10 a is formed in 49 % by a metathesis reaction followed by hydrogenation. Bis‐loop derivative 6 forms no homodimers for steric reasons, but a stoichiometric mixture with the open‐chain tetraalkenyl derivative 7 a contains exclusively the heterodimer. Metathesis and subsequent hydrogenation now yields 65 % of the pure bis[2]catenane 10 a which could not be isolated from the complex reaction mixture obtained from the homodimer 7 a⋅7 a. The chirality of 10 a (D₂ symmetry) has been verified by optical resolution using HPLC on a chiral stationary phase.