Lithium templated synthesis of catenanes: efficient synthesis of doubly interlocked [2]-catenanes

Li+ (3 equiv,) is used as an assembling centre to generate a double-stranded helical complex from two linear coordinating fragments, each containing three 1,10-phenanthroline units and bearing terminal olefins at their ends; ruthenium-catalyzed ring-closing metathesis on the helical precursor leads to a 4-crossing [2]-catenane in 30% yield, making the procedure reasonably preparative.