Synthesis of Cyclic Polymers: Ring-Expansion Reaction of Cyclic <i>S</i>-Dithioester with Thiiranes

Abstract

The ring-expansion reaction of equimolar cyclic dithioester 1 with 3-phenoxypropyrene sulfide (PPS) (cyclic dithioester 1/PPS = 1/2) was examined in the presence of TBAC as a catalyst in NMP for 24 h. It was found that intermolecular ester-exchange reaction occurred during the insertion reaction of PPS into cyclic dithioesters, and cyclic polymers with Mns = 3600−8900 were obtained in 80−96% yields. The structures of the obtained cyclic polymers were confirmed by the 1H NMR, 13C NMR IR, and MALDI TOF-MS spectroscopy. The continuous insertion reaction of excess PPS into cyclic dithioester (cyclic dithioester 1/PPS = 1 /50) was also examined, and it was found that the insertion reaction proceeded quantitatively to afford the corresponding cyclic polysulfide with Mn = 42 000 and Mw/Mn = 4.50 in a 96% yield.