500716-28-9Relevant articles and documents
Unimolecular Anion-Binding Catalysts for Selective Ring-Opening Polymerization of O-carboxyanhydrides
Li, Maosheng,Zhang, Shuai,Zhang, Xiaoyong,Wang, Yanchao,Chen, Jinlong,Tao, Youhua,Wang, Xianhong
, p. 6003 - 6012 (2021/02/01)
Anion-binding can regulate anion transport in chloride channels through dynamic non-covalent interactions, which gives insights into the designing of new organocatalytic transformations but is surprisingly unexplored in polymerization catalysis. Herein, we describe an effective unimolecular anion-binding organocatalysis where 4-(dimethylamino)pyridine is anchored to a thiourea for ring-opening polymerization of O-carboxyanhydrides (OCAs) to furnish highly isotactic poly(phenyllactic acid) (Ph-PLA) with molecular weight (MW) up to 150.0 kDa, which well addresses the formidable challenge of synthesizing high MW stereoregular polyesters. Calculations and experimental studies indicate a dynamic cooperative anion-binding mechanism, where the dynamic anion-binding interaction of thiourea moiety to propagating species facilitates efficient chain propagation and the synergetic decarboxylation retains high selectivity for OCA ring-opening over side reactions (such as cyclization, epimerization, and transesterification).
DMAP-thiourea catalyst and preparation method thereof, and high-molecular-weight biodegradable polyester and preparation method thereof
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, (2021/07/11)
The invention relates to a DMAP-thiourea catalyst and a preparation method thereof as well as high-molecular-weight biodegradable polyester and a preparation method thereof. The DMAP-thiourea catalyst disclosed by the invention has the characteristic of living polymerization when being used for catalyzing ring opening polymerization of O-carboxyl anhydride monomers (OCAs). According to the DMAP-thiourea catalyst disclosed by the invention, a thiourea group is used as Lewis acid, a monomer is activated through a hydrogen bond, DMAP is used as Lewis alkali and a nucleophilic addition monomer, and ring opening polymerization of an OCAs monomer is commonly catalyzed by utilizing an adjacent synergistic effect. Especially, the increased active species are zwitterions, and no alcohol is needed as an initiator. The polymerization speed is high, the reaction temperature is low, and the obtained polyester is high in molecular weight and narrow in distribution. By adjusting the structure of the catalyst, changing the acidity and alkalinity of the catalyst and the steric hindrance of the catalyst and optimizing parameters such as polymerization temperature, concentration and the like, controllable polymerization of the OCAs monomer is realized, and finally, biodegradable polyester with molecular weight as high as 130,000 is obtained.
Synthesis and Characterization of the Most Active Copper ATRP Catalyst Based on Tris[(4-dimethylaminopyridyl)methyl]amine
Ribelli, Thomas G.,Fantin, Marco,Daran, Jean-Claude,Augustine, Kyle F.,Poli, Rinaldo,Matyjaszewski, Krzysztof
, p. 1525 - 1534 (2018/02/09)
The tris[(4-dimethylaminopyridyl)methyl]amine (TPMANMe2) as a ligand for copper-catalyzed atom transfer radical polymerization (ATRP) is reported. In solution, the [CuI(TPMANMe2)Br] complex shows fluxionality by variable-temperature NMR, indicating rapid ligand exchange. In the solid state, the [CuII(TPMANMe2)Br][Br] complex exhibits a slightly distorted trigonal bipyramidal geometry (τ = 0.89). The UV-vis spectrum of [CuII(TPMANMe2)Br]+ salts is similar to those of other pyridine-based ATRP catalysts. Electrochemical studies of [Cu(TPMANMe2)]2+ and [Cu(TPMANMe2)Br]+ showed highly negative redox potentials (E1/2 = -302 and -554 mV vs SCE, respectively), suggesting unprecedented ATRP catalytic activity. Cyclic voltammetry (CV) in the presence of methyl 2-bromopropionate (MBrP; acrylate mimic) was used to determine activation rate constant ka = 1.1 × 106 M-1 s-1, confirming the extremely high catalyst reactivity. In the presence of the more active ethyl α-bromoisobutyrate (EBiB; methacrylate mimic), total catalysis was observed and an activation rate constant ka = 7.2 × 106 M-1 s-1 was calculated with values of KATRP ≈ 1. ATRP of methyl acrylate showed a well-controlled polymerization using as little as 10 ppm of catalyst relative to monomer, while side reactions such as CuI-catalyzed radical termination (CRT) could be suppressed due to the low concentration of L/CuI at a steady state.
Resonance Raman investigation of equatorial ligand donor effects on the CU2O22+ core in end-on and side-on μ-peroxo-dicopper(II) and bis-μ-oxo-dicopper(III) complexes
Henson, Mark J.,Vance, Michael A.,Zhang, Christiana Xin,Hong-Chang, Liang,Karlin, Kenneth D.,Solomon, Edward I.
, p. 5186 - 5192 (2007/10/03)
The effect of endogenous donor strength on CU2O2 bonds was studied by electronically perturbing [{(R-TMPA)CuII}2(O2)]2+ and [{(R-MePY2)Cu}2(O2)]2+ (R = H, MeO, Me2N), which form the end-on μ-1,2 bound peroxide and an equilibrium mixture of side-on peroxo- dicopper(II) and bis-μ-oxo-dicopper(III) isomers, respectively. For [{(R-TMPA)CUII}2(O2)]2+, vo-o shifts from 827 to 822 to 812 cm-1 and VCu-O(sym) shifts from 561 to 557 to 551 cm-1, respectively, as R- varies from H to MeO to Me2N. Thus, increasing the N-donor strength to the copper decreases peroxide π*σ donation to the copper, weakening the Cu-O and O-O bonds. A decrease in vCu-O of the bis-μ-oxo- dicopper(III) complex was also observed with increasing N-donor strength for the R-MePY2 ligand system. However, no change was observed for vO-O of the side-on peroxo. This is attributed to a reduced charge donation from the peroxide π*σ orbital with increased N-donor strength, which increases the negative charge on the peroxide and adversely affects the back-bonding from the Cu to the peroxide σ*orbital. However, an increase in the bis-μ-oxo-dicopper(III) isomer relative to side-on peroxo-dicopper(II) species is observed for R-MePY2 with R = H 2N. This effect is attributed to the thermodynamic stabilization of the bis-μ-oxo-dicopper(III) isomer relative to the side-on peroxo-dicopper(II) isomer by strong donor ligands. Thus, the side-on peroxo-dicopper(II)/bis-μ-oxo-dicopper(III) equilibrium can be controlled by electronic as well as steric effects.
