Techniques regarding the synthesis of polyesters and/or polycarbonates through one or more ring-opening polymerizations conducted within a flow reactor and facilitated by a urea anion catalyst and/or a thiourea catalyst are provided. For example, one or more embodiments can comprise a method, which can comprise polymerizing, via a ring-opening polymerization within a flow reactor, a cyclic monomer in the presence an organocatalyst comprising a urea anion.
Techniques regarding the synthesis of polyesters and/or polycarbonates through one or more ring-opening polymerizations conducted within a flow reactor and facilitated by a urea anion catalyst and/or a thiourea catalyst are provided. For example, one or more embodiments can comprise a method, which can comprise polymerizing, via a ring-opening polymerization within a flow reactor, a cyclic monomer in the presence an organocatalyst comprising a urea anion.
Quantification of Electrophilic Activation by Hydrogen-Bonding Organocatalysts
作者:Ryan R. Walvoord、Phuong N. H. Huynh、Marisa C. Kozlowski
DOI:10.1021/ja5086244
日期:2014.11.12
A spectrophotometric sensor is described that provides a useful assessment of the LUMO-lowering provided by catalysts in DielsAlder and FriedelCrafts reactions. A broad range of 33 hydrogen-bonding catalysts was assessed with the sensor, and the relative rates in the above reactions spanned 5 orders of magnitude as determined via H-1- and H-2 NMR spectroscopic measurements, respectively. The differences between the maximum wavelength shift of the sensor with and without catalyst (Delta lambda max(1)) were found to correlate linearly with ln(k(rel)) values for both reactions, even though the substrate feature that interacts with the catalyst differs significantly (ketone vs nitro). The sensor provides an assessment of both the inherent reactivity of a catalyst architecture as well as the sensitivity of the reaction to changes within an architecture. In contrast, catalyst pK(a) values are a poor measure of reactivity, although correlations have been identified within catalyst classes.
<sup>31</sup>P NMR Spectroscopically Quantified Hydrogen-Bonding Strength of Thioureas and Their Catalytic Activity in Diels-Alder Reactions
作者:Alexander R. Nödling、Gergely Jakab、Peter R. Schreiner、Gerhard Hilt
DOI:10.1002/ejoc.201402871
日期:2014.10
the 31PNMR chemical shifts. A linear correlation between both variables was observed throughout the functionalized thioureas. The 31PNMR probe correlation fared better in comparison to a pKa correlation. Accordingly, the quantification presented herein by using a 31PNMR probe offers an elegant way to estimate the catalyticactivity of thiourea catalysts in hydrogen-bond-activated reactions such