Catalytic Aminolysis Research Articles

Aminolysis of five-membered cyclic carbonate catalyzed by guanidines: Solvent effects on the formation of guanidine dimers

This paper presents an experimental and computational investigation on the aminolysis reactions of five-membered cyclic carbonate (5CC) catalyzed by mono- or bi-cyclic guanidines in various solvents. For both liquid and solid 5CC substrate employed, higher polar solvent favors the monomeric active guanidine responsible for the catalytic aminolysis reactions. The formation of the dimeric state of the guanidine catalyst, which is seemingly inert to catalytic activity, is prevented by the bulkier substituents connecting to the guanidine moiety. Extensive DFT calculations further confirm that the relative stabilities of dimeric guanidine is depended on both the polarities of the solvents and the bulkiness of the substituents connected to the guanidine moiety, which is consistent with the experimental kinetic results.

Chemical recycling of polyester textile wastes using silver-doped zinc oxide nanoparticles: an economical solution for circular economy.

The waste management of polyethylene terephthalate (PET)-derived polyester (PES) textile is a global issue, and material recovery throughchemical recycling can restore a circular economy. In our investigation, microwave-induced catalytic aminolysis and glycolysis of PES textile wastes using Ag-doped ZnO nanoparticles have been proposed. Ag-doped ZnO is prepared by the sol-gel method and characterised by XRD, FT-IR, UV-Vis, SEM-EDX and TEM. The reaction parameters such as PET-to-catalyst ratio, microwave power and irradiation time, temperature and catalyst recycling have been optimised. The catalyst was found to be more stable and could be recycled up to six times without losing its activity. Both theaminolysis and glycolysis of PES showed 100% conversion and afforded of bis (2-hydroxy ethylene) terephthalamide (BHETA) and bis (2-hydroxy ethylene) terephthalate (BHET), respectively. The depolymerisation of PES wastes using Ag-doped ZnO afforded BHETA and BHET for about 95 and 90%, respectively. The monomers BHET and BHETA confirmed by FT-IR, 1H NMR and mass spectroscopy. According to the findings, 2 mol% Ag-doped ZnO has higher catalytic activity.

Robust and Environmentally Benign Solid Acid Intercalation Catalysts for the Aminolysis of Epoxides

AbstractThe catalytic aminolysis of epoxides can lead to a large number of β‐amino alcohols which are of particular interest in industrial applications. In this paper, we demonstrate for the first time the use of a polyoxometalate [CoW12O40]5− intercalated layered double hydroxides (Zn3Al‐LDH) material as an efficient solid acid catalyst for the catalytic aminolysis of various epoxides under mild and solvent‐free conditions. The as‐prepared heterogeneous catalyst Zn3Al‐CoW12 was fully characterized by FT‐IR, powder XRD, TG‐DTA, BET, XPS, SEM, HR‐TEM and NH3‐TPD. The catalytic performance of Zn3Al‐CoW12 for the aminolysis of epoxides revealed excellent yields with high regioselectivity and stereoselectivity. Moreover, the solid acid catalyst can be easily recycled and reused without detectable decrease of its catalytic efficiency.

Terbium–organic framework as heterogeneous Lewis acid catalyst for β‐aminoalcohol synthesis: Efficient, reusable and green catalytic method

A terbium–organic framework (Tb‐MOF) was prepared using a previously reported procedure. Tb‐MOF was characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, powder X‐ray diffraction and surface area analysis. Tb‐MOF was employed as a heterogeneous Lewis acid catalyst for the synthesis of β‐aminoalcohols. Also, the effect of ultrasonic irradiation was examined in the catalytic aminolysis of styrene oxide. The reaction conditions were optimized by variation of reaction time, catalyst concentration and solvent. A variety of β‐aminoalcohols were synthesized and characterized. The Tb‐MOF catalyst showed excellent selectivity and high yield for these transformations.

Facile one-pot synthesis of 5-aryl/heterylidene-2-(2-hydroxyethyl- and 3-hydroxypropylamino)-thiazol-4-ones via catalytic aminolysis

ABSTRACTA multicomponent synthetic approach for 5-aryl/heterylidene-2-(2-hydroxyethylamino)- and 2-(3-hydroxypropylamino)-thiazol-4-ones starting from 2-thioxothiazolidin-4-one or 2-methylsulfanylthiazol-4-one was developed. The proposed method involves simultaneous aminolysis of 2-thioxo- or 2-methylsulfanyl groups and Knoevenagel condensation with (hetero)aromatic aldehydes using 2-aminoethanol or 3-aminopropan-1-ol as catalysts. Side-chain prototropic amino–imino tautomerism was observed for target 5-ylidene-2-alkylaminothiazol-4-ones.

Catalytic Aminolysis (Amide Formation) from Esters and Carboxylic Acids: Mechanism, Enhanced Ionic Liquid Effect, and its Origin

AbstractThis paper describes the use of imidazolium‐based ionic liquids {1‐n‐butyl‐3‐methylimidazolium tetrafluoroborate [BMI‐BF4], 1‐n‐butyl‐3‐methylimidazolium hexafluorophosphate [BMI‐PF6], and 1‐n‐butyl‐3‐methylimidazolium bis(trifluoromethylsulfonyl)imide [BMI‐NTf2]} as efficient supports for Lewis and Brønsted acids ,which are promoters of the aminolysis of some esters, fatty acids, and fatty acid esters (among others) to form amide derivatives. Some esters and carboxylic acids were tested to demonstrate the generality of the methodology, and the corresponding amides were obtained in high yields. Recycling reactions (at least eight reuses) without a notable loss in activity could be performed by using CdO and SnCl2 as catalysts in BMI‐NTf2 as the ionic medium. Brønsted acids, such as H2SO4 and HCl, were also tested with impressive results; however, it was not possible to perform recycling reactions because of catalyst leaching. The same was true when using BF3⋅OEt2 as the catalyst. Mechanistic insights and the ionic‐liquid effect were investigated by using 13C{1H} NMR spectroscopy, which showed that there is a strong interaction of the imidazolium cation with the CO and CC bonds of methyl oleate, most likely through CH⋅⋅⋅π interactions, π‐stacking interactions, and ion‐pair formation in the presence of a metal catalyst. Electrospray ionization–quadrupole time‐of‐flight experiments allowed a better understanding of the reaction mechanism. The results could explain the enhanced ionic‐liquid effect on the stabilization of the formed intermediates, which facilitated the amide bond formation.

Kinetics of the Volume and Surface Reactions in the Phase-Transfer Catalytic Aminolysis of 4-Nitrophenyl Acetate

It was shown that a distribution-type kinetic model can be used to describe the mechanism of the phase-transfer catalytic aminolysis of 4-nitrophenyl acetate with potassium glycinate in chlorobenzene with 18-crown-6 as catalyst. A quantitative assessment was made of the contributions from the reactions in the volume and at the interface in the solid/liquid system.

Catalytic aminolysis of epoxide by alumina prepared from amine-protected Al precursor

The catalytic activities of alumina prepared from an Al alkoxide-amine adduct monomer for the reaction of cyclopentene oxide with piperidine was determined after various pretreatments, including calcination and exposure to moisture. They were compared with the activity of alumina prepared by the conventional hydrolysis method. It was found that the as-prepared sample from the alkoxide-amine monomer preparation was five times more active than a conventional preparation, suggesting that it has a higher density of surface Lewis acid sites. However, its activity was much more severely suppressed by exposure to moisture.

Kinetic studies of guinea pig liver transglutaminase reveal a general-base-catalyzed deacylation mechanism.

Guinea pig liver transglutaminase (TGase) reacts with 0.1 mM N-Cbz-L-Glu(gamma-p-nitrophenyl ester)Gly (5, prepared herein, K(M) = 0.02 mM) to undergo rapid acylation that can be followed spectrophotometrically at 400 nm (pH 7.0, 25 degrees C). Deacylation of the transiently formed thiolester acyl enzyme intermediate via catalytic aminolysis was studied in the presence of six primary amines of widely varying basicity (pK(NH+) = 5.6-10.5). Steady-state kinetic studies were performed to measure k(cat) and K(M) values for each amine substrate. A Brønsted plot constructed through the correlation of log(k(cat)/K(M)) and pK(NH+) for each amine substrate displays a linear free-energy relationship with a slope beta(nuc) = -0.37 +/- 0.08. The shallow negative slope is consistent with a general-base-catalyzed deacylation mechanism in which a proton is removed from the amine substrate during its rate-limiting nucleophilic attack on the thiolester carbonyl. Kinetic isotope effects were measured for four acceptor substrates (water, kie = 1.1 +/- 0.1; aminoacetonitrile, kie = 5.9 +/- 1.2; glycine methyl ester, kie = 3.4 +/- 0.7; N-Ac-L-lysine methyl ester, kie = 1.1 +/- 0.1) and are consistent with a proton in flight at the rate-limiting transition state. The active site general-base implicated by these kinetic results is believed to be His-334, of the highly conserved TGase Cys-His-Asp catalytic triad.

Catalytic aminolysis of acrylic copolymers in solution and in the melt. II. Comparison between styrenic and ethylenic copolymers

AbstractThe aminolysis of poly(styrene‐co‐methyl acrylate) (SMA) by octadecylamine in solution and in the melt has been reported in Part I. We now have studied the aminolysis of poly(ethylene‐co‐methyl acrylate) (EMA) with the same amine in the melt and compared the two sets of data in this paper. With EMA, the data confirmed and precised the catalytic mechanism proposed in Part I. The best tautomeric catalysts are the ones which form an eight‐atom ring structure with the ester and amine groups. With EMA aminolysis is faster than with SMA because of the steric hindrance of phenyl groups in SMA. But EMA aminolysis remains a rather slow reaction. In a corotating twin‐screw extruder the conversion was only around 4% at 220°C with a mean residence time of 150 s. It was also shown that the EMA/octadecylamine/catalyst system, like the SMA system, is homogeneous in the molten state at temperatures around 200°C.

Catalytic aminolysis of acrylic copolymers in solution and in the melt. I. Mechanism and kinetics

AbstractThe aminolysis of poly(styrene‐co‐methyl acrylate) (SMA) by octadecylamine was studied in solution and in the melt at temperatures around 200°C. This reaction is rather slow, so several types of catalysts were tested to accelerate it. The most efficient is 2‐pyridone, a compound in tautomeric equilibrium with 2‐hydroxypyridine. A mechanism of the catalytic reaction is proposed whereby the tautomeric nature of the catalyst plays a key role in a very important step of the reaction, namely the proton transfer. This mechanism is confirmed by the kinetic data determined in a 1,2,4‐trichlorobenzene solution and in the melt. In addition, it was found that the kinetic data obtained in both media are very close, indicating no significant difference of local polarity in the two reaction media. Data also show only a minor effect due to difference in viscosity. Finally, the question of the homogeneity of the molten medium is discussed.