Synthesis and ring-expanding oligomerization of an extremely strained macrocyclic aromatic ether-sulfone

[GRAPHICS] An extremely strained, 5-ring, macrocyclic aromatic ether-sulfone, [-1,4-C6 H4SO2-1,4-C6H4O-1,3-C6H4O-1,4-C6H4SO2-1,4-C6H4-], synthesized by nickel-cat alyzed intramolecular coupling of a bis-chlorophenylene-terminated precurso r, undergoes fluoride-promoted ring expansion in dilute solution, giving a series of higher macrocyclic oligomers including cyclic dimer, trimer, and tetramer. The latter contains 20 aromatic residues in a 92-atom ring and is one of the largest synthetic organic macrocycles to bei crystallographical ly characterized. The synthesis, structure, and ring expansion of a related macrocyclic ether-ketone are also! reported.