A 40‐membered cyclic arylene ether sulfone from bisphenol‐A: improved synthesis and properties

By the use of pseudo‐high dilution techniques a 40‐membered cyclic arylene sulfone 4, n = 1 was produced in 67% yield by “1 + 1 cyclization” of 4,4′‐dichlorodiphenyl sulfone with 4,4′‐bis(p‐hydroxyphenylisopropylidene phenoxy)diphenyl sulfone, derived in turn from bisphenol‐A and the dihalosulfone. This is a significant improvement over our previously reported yield of 11%. However, the use of cesium carbonate did not result in a yield improvement, i.e., no “cesium effect” was observed. The purity of macrocycle 4, n = 1 was established by high‐performance liquid chromatography (HPLC), NMR spectroscopy and fast atom bombardment mass spectrosccopy (FAB MS). Macrocycle 4, n = 1 has poor solubility due to its crystallinity (Tm = ca. 500°C), but does have high thermal stability (5% weight loss at 507°C in air). HPLC and FAB MS demonstrated that other homologous macrocyclic products resulted from “2 + 2 cyclization” (4, n = 3), “3 + 3 cyclization” (4, n = 5) and backbiting ether exchange reactions (4, n = 2). The high melting point of 4, n = 1 precludes its use as a monomer for melt ring opening polymerization, but this study provides a methodology for the synthesis of other cyclic monomers designed to have lower melting points and be useful in melt ring opening polymerizations.