Thioacyl-Transfer Ring-Expansion Polymerization of Thiiranes Based on a Cyclic Dithiocarbamate Initiator

Abstract

We report the novel thioacyl-transfer ring-expansion polymerization (REP) of thiiranes, using 3H-benzothiazol-2-thione (BTT) as the cyclic dithiocarbamate initiator and tetrabutylammonium chloride (TBAC) as the catalyst. REP proceeded in a controlled manner to produce cyclic polysulfides with a narrow M w/M n of 1.1 and whose cyclic structures were confirmed by MALDI-TOF mass spectrometry. Time-course studies revealed unique sigmoidal profiles due to the stable five-membered cyclic structure of the BTT initiator. The GPC curves were analyzed by the Gaussian fitting method, which revealed that the cyclic polymers are accompanied by another fraction with nearly twice the molecular weight of the main product due to ring-crossover reactions between cyclic polysulfides during REP. The BTT-initiated cyclic polysulfides produced in this manner act as macroinitiators for the REP of thiiranes, highlighting the living characteristics of the BTT-initiated REP developed herein. Post-polymerization further enabled the preparation of cyclic block copolymers with different combinations of thiiranes.

Synthesis of cis-thiiranes as diastereoselective access to epoxide congeners via 4π-electrocyclization of thiocarbonyl ylides

“…The sulfur congeners, thiiranes are also useful synthetic precursors that can be transformed into an array of functional groups via ring-opening or desulfurization [14][15][16][17][18][19][20] . In addition, versatile sulfur-containing polymers can be produced via ring-expansion polymerizations or copolymerizations [21][22][23][24][25] . Moreover, thiiranes have been examined as analogs of biologically active oxiranes [26][27][28] , and several derivatives showed inhibitory activity against gelatinases 29,30 .…”