Bis- and Tris-Urea H-Bond Donors for Ring-Opening Polymerization: Unprecedented Activity and Control from an Organocatalyst
Document Type
Article
Date of Original Version
8-16-2016
Abstract
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.
Publication Title, e.g., Journal
ACS Macro Letters
Volume
5
Issue
8
Citation/Publisher Attribution
Fastnacht, Kurt V., Samuel S. Spink, Nayanthara U. Dharmaratne, Jinal U. Pothupitiya, Partha P. Datta, Elizabeth T. Kiesewetter, and Matthew K. Kiesewetter. "Bis- and Tris-Urea H-Bond Donors for Ring-Opening Polymerization: Unprecedented Activity and Control from an Organocatalyst." ACS Macro Letters 5, 8 (2016): 982-986. doi: 10.1021/acsmacrolett.6b00527.