Non-cross-linked polystyrene-supported 2-imidazolidinone chiral auxiliary: synthesis and application in asymmetric alkylation reactions

Abstract

SummaryAsymmetric alkylation reactions using non-cross-linked polystyrene (NCPS)-supported 2-imidazolidinone chiral auxiliaries were successfully investigated with excellent diastereocontrol (>99% de). The recovery and the recycling of this soluble polymer-supported chiral auxiliary were achieved in order to produce highly optical pure carboxylic acids.

Continuous Flow Synthesis of 2-Imidazolidinone from Ethylenediamine Carbamate in Ethylenediamine Solvent over the CeO2 Catalyst: Insights into Catalysis and Deactivation

“…2-Imidazolidinone, also called ethylene urea (EU), is the simplest cyclic urea derivative and is used as a precursor to polymers, medicines, and agrochemicals. , EU is currently produced from ethylenediamine (EDA) and a toxic carbonyl source, phosgene . Meanwhile, the direct synthesis of EU from EDA and CO 2 has also been reported.…”

Improvement of Stability of CeO2–Based Catalysts by Mn Doping for the Synthesis of 2-Imidazolidinone from Ethylenediamine Carbamate

“…This liquid was then diluted with 100 g of EDA and stirred well at room temperature. The composition of this mixture was determined as approximately 32 wt % EDA and 68 wt % EDA-CA by 1 H nuclear magnetic resonance spectroscopy ( 1 H NMR; AV-400, Bruker, superconducting magnet 9.4 T, 1 H 400 MHz, deuterated solvent methanol-d 4 , internal standard naphthalene), whose data were managed using the JEOL Delta version 5.3.3 software. This mother solution was diluted further with EDA before each catalytic reaction.…”

“…Although it was better to compare the Mn-1.0-CeO 2 -873(Co-precip) catalyst with another control material, MnO 2 , which has recently been reported as a catalyst for the synthesis of urea derivatives from CO 2 and amines, 6,7 the dissolution and reprecipitation of Mn species in the flow reactor prevented the reaction operation due to the tube clogging. Even when the reaction with MnO 2 was operated by using a batch reactor, the resulting reaction mixture could not be measured by 1 H NMR due to the dissolution of paramagnetic Mn species.…”

“…The internal standard used for GC analyses was tert-butyl alcohol. The reaction mixture was also analyzed by 1 H NMR spectroscopy with tert-butyl alcohol and methanol-d 4 as the internal standard and deuterated solvent, respectively. Consistent with our previous works, 11−13 the unreacted EDA-CA was quantified via 1 H NMR spectroscopy due to its thermal decomposition into EDA and CO 2 in the vaporization chamber of the GC.…”

“…Although the modification with Mn was effective for the improvement of the catalyst stability of CeO 2 (HS), the reaction mixture given by Mn-1.0/ CeO 2 (HS,Imp) provided broad signals in its 1 H NMR spectrum. Because of such signal broadening, the estimation of EDA-CA conversion was impossible in the case of Mn-1.0/ CeO 2 (HS,Imp) because the quantity of unreacted EDA-CA needs to be determined by 1 H NMR spectroscopy instead of GC-FID (see the Experimental Section). This phenomenon found in the 1 H NMR spectrum was caused possibly by contamination of paramagnetic Mn species from Mn-1.0/ CeO 2 (HS,Imp) into the reaction mixture.…”