Synthesis of Thermoresponsive Polyurethane from 2‐Methylaziridine and Supercritical Carbon Dioxide

Abstract

Under pressure: Temperature‐dependent optical transmission in aqueous solution is exhibited by polyurethanes that are obtained by copolymerization of 2‐methylaziridine and supercritical CO2 (scCO2; see scheme). The transmittance drops sharply at the lower critical solution temperature (LCST). The molecular weight, content of urethane linkages, and LCST value of the polyurethanes are controllable simply by changing the CO2 pressure.

Proline-Catalyzed Synthesis of 5-Aryl-2-oxazolidinones from Carbon Dioxide and Aziridines Under Solvent-Free Conditions

“…While higher pressure may suppress the interaction between the substrate and the catalyst, and it may also cause a low concentration of aziridine around the catalyst, thereby leading to lower activity (entry 9). [37] Furthermore, a series of catalytic cycles were performed to survey the reusability of the catalyst (entries [10][11][12][13][14]. The particular polarity of proline could provide a convenient protocol for the catalyst recovery.…”

“…It is also interesting that the chemoselectivity of 2a also rose from 56% to 91% as reaction time was prolonged from 1 to 8 h, which could be explained by backbiting from the oligomers or copolymerization between aziridines and CO 2 , as depicted in the literature. [36][37][38]51,52] The effect of reaction temperature on the reaction was studied at the pressure of 6 MPa for 8 h (entries 4, 6, and 7). The reaction temperature had a remarkable effect on the reactivity.…”

“…; [15][16][17][18][19][20][21] (ii) reaction of propargylamines or propargylic alcohols with CO 2 ; [22][23][24][25][26] (iii) carboxylation of aziridines with CO 2 . [27][28][29][30][31][32][33][34][35][36][37][38][39] Recently, Li et al demonstrated that the oxazolidinones can be synthesized through the copper-catalyzed coupling of aldehydes, amines, terminal alkynes, and CO 2 . [40] Method (iii) is a high-atom-efficiency reaction, utilizing renewable, abundant, and nontoxic CO 2 as a building block, and it has attracted much attention from the viewpoint of green chemistry.…”

“…[40] Method (iii) is a high-atom-efficiency reaction, utilizing renewable, abundant, and nontoxic CO 2 as a building block, and it has attracted much attention from the viewpoint of green chemistry. In past decades, numerous homogeneous catalytic systems including salen Cr(III)=dimethylamino-pyridine (DMAP), [27] phenol=DMAP, [28] alkali metal halide [29,30] or tetraalkylammonium halide system, [31] iodine, [32 , 33] PEG 6000 NBu 4 Br, [37] zirconyl chloride, [38] and a-amino acid [39] have been reported to be effective for the coupling of aziridines and CO 2 . Besides, an electrochemical procedure is an alternative for this transformation.…”

Poly(hydroxy urethane)s based on renewable diglycerol dicarbonate

“…However, the production of polyurethanes has remained a major concern as it involves the synthesis and use of toxic diisocyanates [1]. Several chemical routes have been developed throughout the years to avoid these issues, yet none of these pathways is currently used for the large scale production of non-isocyanate polyurethanes (NIPU) [2][3][4][5][6][7][8]. Still, the addition reaction between cyclic carbonates and amines to form poly(hydroxy urethane)s (PHU) has recently been highlighted in an increasing number of publications [9][10][11][12][13][14].…”