Synthesis of novel interlocked systems utilizing a palladium complex with 2,6-pyridinedicarboxamide-based tridentate macrocyclic ligand

A new protocol for the high yield synthesis of interlocked molecules is described. Palladium(II) complex including a 2,6-pyridinedicarboxamide-based tridentate macrocycle 2 was allowed to react with a 2,6-disubstituted pyridine derivative bearing two hydroxyl groups at both termini 3b to yield the corresponding Pd(II) complex 4b quantitatively. An acid catalyzed end-capping of 4b with a bulky isocyanate gave Pd(II) complex 5b in 96% yield, which was treated with carbon monoxide to afford [2]rotaxane 6b quantitatively.