Bis- and Tris-Urea H‑Bond Donors for Ring-Opening Polymerization: Unprecedented Activity and Control from an Organocatalyst

• Published in: ACS macro letters Vol. 5; no. 8; pp. 982 - 986
• Main Authors: Fastnacht, Kurt V, Spink, Samuel S, Dharmaratne, Nayanthara U, Pothupitiya, Jinal U, Datta, Partha P, Kiesewetter, Elizabeth T, Kiesewetter, Matthew K
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 16-08-2016
• ISSN: 2161-1653; 2161-1653
• DOI: 10.1021/acsmacrolett.6b00527

A new class of H-bond donating ureas was developed for the ring-opening polymerization (ROP) of lactone monomers, and they exhibit dramatic rate acceleration versus previous H-bond mediated polymerization catalysts. The most active of these new catalysts, a tris-urea H-bond donor, is among the most active organocatalysts known for ROP, yet it retains the high selectivity of H-bond mediated organocatalysts. The urea cocatalyst, along with an H-bond accepting base, exhibits the characteristics of a “living” ROP, is highly active, in one case, accelerating a reaction from days to minutes, and remains active at low catalyst loadings. The rate acceleration exhibited by this H-bond donor occurs for all base cocatalysts examined. A mechanism of action is proposed, and the new catalysts are shown to accelerate small molecule transesterifications versus currently known monothiourea catalysts. It is no longer necessary to choose between a highly active or highly selective organocatalyst for ROP.