Specific behaviour of cycloolefins in ring-opening polymerisation

The catalytic activity and high selectivity reported by bimetallic heteroscorpionate acetate zinc complexes in ring-opening copolymerization (ROCOP) reactions involving CO2 as substrate encouraged us to expand their use as catalysts for ROCOP of cyclohexene oxide (CHO) and cyclic anhydrides. Among the catalysts tested for the ROCOP of CHO and phthalic anhydride at different reaction conditions, the most active catalytic system was the combination of complex 3 with bis(triphenylphosphine)iminium as cocatalyst in toluene at 80 °C. Once the optimal catalytic system was determined, the scope in terms of other cyclic anhydrides was broadened. The catalytic system was capable of copolymerizing selectively and efficiently CHO with phthalic, maleic, succinic and naphthalic anhydrides to afford the corresponding polyester materials. The polyesters obtained were characterized by spectroscopic, spectrometric, and calorimetric techniques. Finally, the reaction mechanism of the catalytic system was proposed based on stoichiometric reactions.

Fast synthesis of high molecular weights polydiethylsiloxanes and random poly(dimethylsiloxane-co-diethylsiloxane) copolysiloxanes via cyclic trimeric phosphazene base catalyzed ring-opening (co)polymerization

The calculation of the main characteristics of the branching of the polymer is presented in the article using the example of polymerization of butadiene in the presence of an organolithium catalytic system modified with polyfunctional sodium and magnesium alcoholates. The addition of a modifier to the catalytic system leads to the participation in the polymerization of at least two types of active centers, which is the reason for some branching of macromolecules. The complemented mathematical model of the periodic process, taking into account the exchange of activity between the two centers, allows to calculate the main characteristics of branching.

Advances in urea and thiourea catalyzed ring opening polymerization: A brief overview

Abstract: This study investigates the use of ionic liquids (ILs) immobilized on HT-clay as catalysts for the Baylis-Hillman reaction. The catalytic system comprised three different types of ILs ([HIM]Im, [BIM]Im, [EIM]Im) and exhibited high reactivity, and the B-H products were obtained in good yield, which is superior to previously reported catalytic systems, whether they were heterogeneous or homogeneous. The HT-clay immobilized with ILs also allowed for easy recovery from the reaction mass and could be recycled for up to 7 consecutive runs with only a slight decrease in activity. Moreover, the scope of our catalytic system was extended to synthesize biologically active lactone ceramide analogs using the Baylis-Hillman reaction at room temperature with (S-) Garner aldehyde and methyl acrylate. The synthesis was successful, and we obtained good yields of the desired products, highlighting the versatility of the ionic liquid immobilized HT-clay catalytic system. This study demonstrates the potential of ionic liquid immobilized HT-clay as a promising catalyst for various organic reactions. Our findings emphasize the importance of developing efficient and environmentally friendly methods for synthesizing valuable organic compounds. The results obtained from this study provide a significant contribution to the ongoing research in the field of catalysis and will be useful for developing new approaches to the synthesis of complex organic molecules.

CuO/AB was found to be a simple and efficient catalyst for the N-arylation of a variety of nitrogen-containing heterocycles, giving the products in excellent yields.

The use of copper and rhodium catalysts separately and in combination directs reactions between vinyldiazoacetates 3 and cinnamaldehydes 2 to from formal [4+3]-cycloaddition (epoxidation followed by Cope rearrangement), intramolecular cyclopropanation, and Mukaiyama-aldol reactions selectively and in high yield.

This article demonstrates the synthesis of a new kind of cationic poly(δ-valerolactone) with primary amino groups at α-positions (poly(α-NH2-VL)) via ring-opening polymerization (ROP) of α-NHBoc-valerolactone (α-NHB-VL) followed by a simple deprotection reaction. The ROP of α-NHB-VL using benzyl alcohol as an initiator and DBU/TU (1,8-diazabicyclo[5.4.0]undec-7-ene/thiourea) as a catalytic system in THF at room temperature afforded poly(α-NHB-VL) with narrow molecular weight distribution. The 1H NMR and MALDI-TOF MS analysis of poly(α-NHB-VL) indicated that each polymeric chain was capped by the initiator. Kinetic experiments confirmed the living nature of the DBU/TU-catalyzed ROP of α-NHB-VL in THF. The copolymerization result indicated that the polymerization activity of α-NHB-VL is comparable to that of ε-caprolactone (CL) and VL. In addition, block copolymers containing poly(α-NHB-VL) were successfully synthesized regardless of whether hydrophilic PEG or hydrophobic PCL was used as the macroinitiator. Moreover, water-soluble poly(α-NH2-VL) was obtained by treatment with trifluoroacetic acid (TFA). It was found that poly(α-NH2-VL) degraded more slowly at pH 5.5 than at pH 7.4 through a hydrolysis kinetics study.

Reductive and oxidative activation of oxygen for selective oxygenation of hydrocarbons

The activity of organoaluminium complex compounds during polymerization of butadiene-1,3 3ith the CoCl 2·(C 5H 5N) 2AlR 2Cl catalytic system

Initiator systems for radical polymerization, having in its composition of several functional groups of interest in terms of creating new methods to control the polymer chain growth in radical polymerization, as it gives the opportunity to influence the molecular-mass characteristics of the products, on the kinetic parameters of the process, and in some cases, the composition and structure of polymers. The work examines the process of polymerization of vinyl monomers in the presence of a new initiating complexes of N,N’-dioxaphosphorinanes aniline (DOPA) + benzoyl peroxide, N,N’-dioxaphosphorinanes toluidine (DОPT) + benzoyl peroxide) and identified the mechanism of interaction of the initiating agents in the formation of the catalytic complex. In experiments was used a dilatometric technique. The polymerization was carried out at different temperatures (60, 80, 100 °C for styrene and 40, 60, 80 °C for methyl methacrylate). Determination of molecular weight of the styrene and methyl methacrylate were produced on the basis of measurements of the intrinsic viscosity of its solutions in toluene. Analyzed kinetics of radical polymerization of styrene and methyl methacrylate in the presence of initiating agents, benzoyl peroxide and DOPA, benzoyl peroxide and DОPT. Determined kinetic parameters of the polymerization of vinyl monomers in the presence of new catalytic systems. The rate of polymerization significantly depends on the concentration of the initiating agents. At high amine concentrations that exceed the peroxide content, there is a rapid expenditure of benzoyl peroxide. Established that tertiary aromatic amines oxopropylidene affect the increase in the rate of initiation of radical polymerization at moderately low temperatures. The proposed mechanism of radical polymerization of vinyl monomers in the presence of initiating system benzoyl peroxide DOPT.

Background: Biginelli reaction is the most well-known and widely studied, multicomponent reaction used for the direct synthesis of many biologically active 3,4-dihydropyrimidin- 2(1H)-ones and their derivatives by reacting a β-keto ester/1,3-dicarbonyl compound, an aldehyde, and urea. It is catalyzed by different Bronsted and Lewis acids. Methods: The catalytic effect of different metal chlorides, such as sodium, potassium, magnesium, stannous, ferric, manganese, cupric, nickel, cobalt, and zinc, in absence and presence of acetic acid were studied. Results: The zinc, ferric, cupric, and cobalt chlorides were found to be more effective catalysts for Biginelli reaction at room temperature. The yield of the reaction increased with temperature for all catalytic systems. Acetophenone, cyclohexanone, acetyl acetone, and different β-ketoesters formed tetrahedropyrimidine in moderate to good yield, by using zinc chloride catalyst at room temperature in acetic acid. The efficiency of the catalyst was studied by treating different substituted aldehydes with 1,3-dicarbonyl compounds and urea at room temperature. Conclusion: The zinc chloride in acetic acid found to be an effective greener catalyst system for Biginelli reaction.

Development of catalytic asymmetric synthesis of indanones via an enantioselective 1,1-carbene migratory insertion/carbopalladation cascade is achieved. In this enantioselective reaction, the in situ generated enantioenriched unstable η3-benzyl Pd species is trapped by an intramolecular olefin to access chiral indanone scaffolds at room temperature with yields up to 96% and e.r. up to 96:4. This methodology is unique in the generation of carbenes from N-tosylhydrazones at room temperature and tolerance for diverse functional groups with catalyst loading as low as 3 mol % and ligand loading of 9 mol %. The catalytic system is found to exhibit asymmetric amplification, giving insight into the structure of the active catalytic species and the catalytic cycle involved. Also, a photokinetic study of the isomerization of the pendant alkene in the synthesized indanone core is reported.

Poly(disulfide)s are an emerging class of sulfur-containing polymers with applications in medicine, energy, and functional materials. However, the constituent dynamic covalent S-S bond is highly reactive in the presence of the sulfide (RS-) anion, imposing a persistent challenge to control the polymerization. Here, we report an anion-binding approach to arrest the high reactivity of the RS- chain end to control the synthesis of linear poly(disulfide)s, realizing a rapid, living ring-opening polymerization of 1,2-dithiolanes with narrow dispersity and high regioselectivity (Mw/Mn ∼ 1.1, Ps ∼ 0.85). Mechanistic studies support the formation of a thiourea-base-sulfide ternary complex as the catalytically active species during the chain propagation. Theoretical analyses reveal a synergistic catalytic model where the catalyst preorganizes the protonated base and anionic chain end to establish spatial confinement over the bound monomer, effecting the observed regioselectivity. The catalytic system is amenable to monomers with various functional groups, and semicrystalline polymers are also obtained from lipoic acid derivatives by enhancing the regioselectivity.

Synthesis of monomer-recyclable polyesters solely from CO2 and bulk olefins holds great potential in significantly reducing CO2 emissions and addressing the issue of plastic pollution. Due to the kinetic disadvantage of direct copolymerization of CO2 and bulk olefins compared to homopolymerization of bulk olefins, considerable research attention has been devoted to synthesis of polyester via the ring-opening polymerization (ROP) of a six-membered disubstituted lactone intermediate, 1,2-ethylidene-6-vinyl-tetrahydro-2H-pyran-2-one (𝜹-L), obtained from telomerization of CO2 and 1,3-butadiene. However, the conjugate olefin on the six-membered ring of 𝜹-L leads to serious Michael addition side reactions. Thus, the selective ROP of 𝜹-L, which can precisely control the repeating unit for the production of polyesters potentially amenable to efficient monomer recycling, remains an unresolved challenge. Herein, the first example of selective ROP of 𝜹-L is reported using a combination of organobase and N,N'-Bis[3,5-bis(trifluoromethyl)phenyl]urea as the catalytic system. Systematic modifications of the substituent of the urea show that the presence of electron-deficient 3,5-bis(trifluoromethyl)-phenyl groups is the key to the extraordinary selectivity of ring opening over Michael addition. Efficient monomer recovery of oligo(𝜹-L) is also achieved under mild catalytic conditions.