Thiazolium as Single-Group Bifunctional Catalyst for Selectively Bulk Melt ROP of Cyclic Esters

Novel single-group bifunctional hydrogen-bonding catalysts based on thiazolium were developed. The integration of hydrogen-bonding donor and acceptor in a single thiazolium ring not only amplified synergetic effect, but also enhanced the stability and the controllability for catalysis, and hence prompt thiazolium an efficient metal-free catalyst for melt ROP of cyclic esters. More interestingly, thiazolium may form a compacted active center with monomer and initiator (or propagating chain end), thus enabling it to selectively activate lower sterically encumbered substrates in ROP.