Synthesis, Characterization, and Copper(II) Chelates of 1,11-Dithia-4,8-diazacyclotetradecane.

Synthesis of 1,11-dithia-4,8-diazacyclotetradecane (L1), a constitutional isomer of the macrocyclic [14]aneN2S2 series, is accompanied with reaction and method optimization. Chelation of L1 with copper(II) provided assessment of lattice packing, ring contortion, and evidence of conformational fluxionality in solution through two unique crystal structures: L1Cu(ClO4)2 and [(L1Cu)2μ-Cl](ClO4)3. Multiple synthetic approaches are presented, supplemented with reaction methodology and reagent screening to access [14]aneN2S2 L1. Reductive alkylation of bis-tosyl-cystamine was integrated into the synthetic route, eliminating the use and isolation of volatile thiols and streamlining the synthetic scale-up. Late-stage cleavage of protecting sulfonamides was addressed using reductive N-S cleavage to furnish macrocyclic freebase L1.