N-甲基b-磺内酰胺氨解反应机理的理论研究

The aminolysis and the effect of water on the aminolysis processes of n-methyl β-sultam have been studied using density functional theory （DFF） method at the B3LYP/6-31G＊ level. The stationary structures and energies have been investigated for both reactions to find two different reaction channels. Specific and general solvent effects have been evaluated and the most favored pathway was found. The presence of solvent disfavors the reaction, whereas the participation of water in the aminolysis reaction plays a positive role and reduces the activation energy greatly. All transition states in the assisted aminolysis are 35-70 kJ/mol lower than those for the non-assisted reaction.     

Synthesis of polysiloxanes containing trifluoroethylene aryl ether groups: The effect of promoters

Polysiloxanes with high molecular weight (M_n > 100 000, M_w/M_n < 2.2) containing various quantity of trifluoroethylene aryl ether groups were prepared by anion ring opening polymerization (AROP) in the presence of promoters including N,N‐dimethylformamide (DMF) and N‐methyl pyrrolidone (NMP). The structures of monomers and polymers were characterized by FTIR and NMR. It was found that the addition of promoter could significantly increase the polymerization rate, decrease the polymerization temperature, and increase the molecular weight of the polymer. When DMF as the promoter, the optimal conditions for polymerization were as follows: The polymerization temperature is 100°C, the amount of catalyst is 2.0%, and the molar ratio of promoter to catalyst is 160:1. The optimal conditions for polymerization using NMP as the promoter were as follows: The polymerization temperature is 75°C, the amount of catalyst is 2.0%, and the molar ratio of promoter to catalyst is 70:1, which indicated that NMP is more effective on AROP than DMF. Thermogravimetric analysis (TGA) showed that the polymer has good heat temperature resistance. Differential scanning calorimetry (DSC) showed that the introduction of NMP in bulk polymerization could improve the randomness of polymer structure, which leads to the disappearance of crystal peak and improve the low temperature resistance of polymer.     

Metal-Free Photoredox-Catalyzed Hydrodefluorination of Fluoroarenes Utilizing Amide Solvent as Reductant

A metal-free photoredox-catalyzed hydrodefluorination of fluoroarenes was achieved by using N,N,N’,N’-tetramethyl-para-phenylenediamine ( 1 ) as a strong photoreduction catalyst. This reaction was applicable not only to electron-rich monofluoroarenes but also to polyfluoroarenes to afford non-fluorinated arenes. The experimental mechanistic studies indicated that the amide solvent NMP plays an important role for regeneration of the photocatalyst, enabling additive-free photoreduction catalysis.     

Calcined Mg-Al Layered Double Hydroxide as a Heterogeneous Catalyst for the Synthesis of Urea Derivatives from Amines and CO2

The calcined Mg‐Al layered double hydroxides (LDHs) with a Mg/Al molar ratio of 3:1 were synthesized and characterized thoroughly by X‐ray diffraction (XRD), temperature‐programmed desorption (TPD) of CO₂, and thermogravimetric analysis (TGA). Thus the calcined Mg‐Al LDHs were used as catalyst for the catalytic synthesis of disubstituted ureas from amines and CO₂. The effects of reaction time, reaction temperature, pressure, solvent and calcined temperature on activity have been investigated. The results indicated that aliphatic amines, cyclohexylamine and benzylamine can be converted to the corresponding ureas selectively over the calcined Mg‐Al LDHs catalysts with N‐methyl‐2‐pyrrolidone (NMP) as solvent without using any dehydrating regent. The catalyst can be recycled several times with only slight loss of activity.     

Synthesis of polymers with pendant hydroxyl groups by polyaddition of bis(oxetane)s with dithiols

Addition reaction of (3-methyl-3-oxetanyl)methyl acetate (MOMA) with bis(4-mercaptophenyl) sulfide (BMPS) was examined in certain organic solvents. When the reaction of MOMA with BMPS was performed without any catalyst in hexamethylphosphoric triamide (HMPA) and N-methyl-2-pyrrolidone (NMP) at 130°C for 24 h, conversions of the corresponding adduct were 96 and 36%, respectively, which was confirmed by ¹H-NMR spectra. On the other hand, when the reaction was carried out using tetraphenylphosphonium bromide (TPPB) as a catalyst under the same conditions, conversions of the adduct were 96 and 81% in HMPA and NMP, respectively. This result shows that although the addition reaction of oxetane compound with aromatic dithiol proceeds without any catalyst in HMPA, the reaction was strongly enhanced by adding TPPB in NMP. On the basis of the above results, polyadditions of bis((3-methyl-3-oxetanyl)methyl) terephthalate (BMOT) and bis((3-ethyl-3-oxetanyl)methyl) terephthalate with BMPS were performed using TPPB as the catalyst in NMP at 130°C for 24 h. As a result, the corresponding high molecular weight polymers 1 (M_n = 22,400) and 2 (M_n = 12,800) with pendant primary hydroxyl groups were obtained in 83 and 89% yields without any gel products, respectively. Furthermore, a low molecular weight oligomer was obtained from the polyaddition of BMOT with aliphatic dithiol, bis(mercaptomethyl)benzene, under the same reaction conditions. The catalytic activity on the polyaddition of BMOT with BMPS was also examined, and it was found that thermally stable TPPB and crown ether complexes at the reaction temperature (130°C) have higher catalytic activity than tetrabutylammonium bromide and tetrabutylphosphonium bromide to produce polymer 1 with high molecular weight. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 2873–2880, 1998     

Synthesis and properties of renewable nonisocyanate polyurethanes (NIPUs) from dimethylcarbonate

Novel fully renewable AA‐BB type nonisocyanate polyurethanes (NIPUs) were synthesized using the transurethanization approach. Dicarbamate monomers were prepared by the reaction of a diamine with an excess of dimethylcarbonate (DMC), in presence of 1,5,7‐triazabicyclo[4.4.0]dec‐5‐ene (TBD) as catalyst. Then, the dicarbamate was reacted with a diol to afford the polymer, in presence of TBD or K₂CO₃ as catalyst. Several renewable diamines and diols were tested. The two steps were conducted under neat conditions. The obtained materials exhibited T_g values varying from ?38 to 42 ° C, T_m values varying from 42 to 204 °C , and thermal stabilities above 200 ° C. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1351–1359     

Acceleration effects of 1,5,7‐triazabicyclo[4.4.0]dec‐5‐ene with 2‐methylimidazole‐intercalated α‐zirconium phosphate as a latent thermal initiator in the reaction of glycidyl phenyl ether and hexahydro‐4‐methylphthalic anhydride

The catalytic effects of 1,5,7‐Triazabicyclo[4.4.0]dec‐5‐ene (TBD) with 2‐methylimidazole‐intercalated α‐zirconium phosphate (α‐ZrP?2MIm) in the reaction of glycidyl phenyl ether (GPE) and hexahydro‐4‐methylphthalic anhydride (MHHPA) were investigated. The reaction did not proceed within 1 h at 60 °C. On increasing the temperature to 100 °C, the conversion reached 93% for 1 h. Without the addition of TBD, the conversion was 67% at 100 °C for 1 h. Under storage conditions at 25 °C for 7 days, the conversion of GPE was only 18%. The curing behavior of 2,2‐bis(4‐glycidyloxyphenyl)propane (DGEBA) and MHHPA in the presence of TBD with α‐ZrP?2MIm was evaluated by differential scanning calorimetry. The addition of TBD with α‐ZrP?2MIm as a latent thermal initiator, the storage stability was maintained and the reaction proceeded rapidly under heating conditions. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 2557–2561     

Influence of the solvent and of the reaction concentration for palladium-catalysed direct arylation of heteroaromatics with 4-bromoacetophenone

The solvent is certainly one of the main sources of wastes during palladium-catalysed direct arylation reactions. We found that such direct arylations of heteroaromatics can be performed using very high concentrations of reactants (0.5 M–5 M). However, the Pd catalyst precursor used must be adapted to both the solvent nature and the concentration of reactants. The reactions performed in DMA, NMP or DMF can be carried out in very concentrated reaction mixtures using 0.1 mol% Pd(OAc)₂ catalyst without phosphine ligand. On the other hand, the reactions in CPME, pentan-1-ol or diethylcarbonate should be performed with a palladium catalyst associated with a phosphine ligand. These reaction conditions allow us to reduce the amount of wastes formed in the course of these couplings.     

High-molecular-weight polyterephthalamide by direct polycondensation reaction in the presence of poly(ethylene oxide)

Polyterephthalamides of high molecular weight (η_inh up to 1.9) were obtained by the direct polycondensation reaction of terephthalic acid and aromatic diamines in the presence of poly(ethylene oxide) (PEO) with triphenyl phosphite in a N-methylpyrrolidone (NMP)–pyridine solution that contained lithium chloride. The molecular weights of the polymers produced varied with the amount and molecular weight of PEO, which showed maximum values when PEO with a molecular weight of 2.0 × 10⁴?5.0 × 10⁵ was used in a concentration of about 0.5 wt % in the solvent. The polycondensation reaction was significantly affected by the level of pyridine in a mixed solvent of NMP and pyridine and by the concentration of the lithium chloride added.     

Rapid Hyperbranched Polythioether Synthesis Through Thiol-Michael Addition Reaction

In this study, two types of hyperbranched (HB) polythioether could readily be achieved in a short time at ambient temperature through a thiol-Michael addition reaction. Dimethyl acetylenedicarboxylate (DMADC) or methyl propiolate (A₂) and trimethylolpropane tris(3-mercaptopropionate) (B₃) monomers were reacted using an organobase 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) as a catalyst in chloroform at room temperature to provide subsequent HB polythioethers. The effect of TBD concentration on the polymerization was studied for the DMDAC case monitoring the molecular weight evolution against time. HB polythioethers were characterized using spectroscopic (nuclear magnetic resonance) and chromatographic (gel permeation chromatography with refractive index and light-scattering detectors) techniques. © 2020 Wiley Periodicals, Inc. J. Polym. Sci. 2020 , 58, 824–830     

Lipase-Catalyzed Synthesis of Carboxylic Amides: Nitrogen Nucleophiles as Acyl Acceptor

 The lipase-catalyzed aminolysis of carboxylic esters is a fairly general reaction that has been performed with a wide range of esters and amines, generally in anhydrous organic media to avoid undesirable hydrolysis of the ester. Alternatively, carboxylic amides can be synthesized by lipase mediated condensation of carboxylic acids and amines if an excess of either reactant is avoided. Chiral carboxylic esters have been resolved by lipase-catalyzed aminolysis. In the majority of these resolutions, Candida antarctica lipase B has been employed as the catalyst. A range of chiral amines has been resolved by lipase mediated acylation, using mainly the lipases from C. antarctica (B type) and Pseudomonas species. The enantiorecognition was frequently found to depend critically on the acylating agent and the reaction medium.     

Stereospecific Radical Polymerization of a Side-Chain Transformable Bulky Acrylamide Monomer and Subsequent Post-Polymerization Modification for Syntheses of Isotactic Polyacrylate and Polyacrylamide

We report syntheses of isotactic polyacrylate and polyacrylamide via a stereospecific radical polymerization of a pendant-transformable monomer, acrylamide carrying isopropyl-substituted ureidosulfonamide ( 1 ), followed by post-polymerization modification (PPM). The study in the alcoholysis and aminolysis reactions of the model compound ( 2 ) for evaluation of the transformation ability of the electron-withdrawing pendant group on the repeating unit 1 revealed the following points: the pendant of the polymer became more reactive than that of monomer; the pendant was active enough for aminolysis reaction affording the amide compound quantitatively without additive/catalyst; the addition of a lithium triflate [Li(OTf)] and triethylamine (Et₃N) was effective as for promotion of the alcoholysis reaction. Poly(methyl acrylate) (PMA) was quantitatively obtained via the radical polymerization of 1 in the presence of Li(OTf) at 60 °C and the subsequent addition of methanol along with Et₃N. Thus-obtained PMA showed higher isotacticity [m=74 %] than that directly obtained via radical polymerization of methyl acrylate (MA) (m=51 %). The isotacticity was further increased as the temperature and monomer concentration were lower, and eventually m was increased up to 93 %. The aminolysis PPM after the iso-specific radical polymerization of 1 gave various isotactic polyacrylamides carrying different alkyl pendant groups, including poly(N-isopropylacrylamide) (PNIPAM).     

Kinetics and mechanism of the aminolysis of O‐phenyl 4‐nitrophenyl dithiocarbonate in aqueous ethanol

The reactions of the title substrate (1) with a series of secondary alicyclic amines are subjected to a kinetic investigation in 44 wt% ethanol‐water, at 25.0°C, ionic strength 0.2 M (KCl). Under amine excess over the substrate, pseudo‐first‐order rate coefficients (k_obs) are obtained. Plots of k_obs against [NH], where NH is the free amine, are nonlinear upwards, except the reactions of piperidine, which show linear plots. According to the kinetic results and the analysis of products, a reaction scheme is proposed with two tetrahedral intermediates, one zwitterionic (T^±) and another anionic (T⁻), with a kinetically significant proton transfer from T^± to an amine to yield T⁻ (k₃ step). By nonlinear least‐squares fitting of an equation derived from the scheme to the experimental points, the rate microcoefficients involved in the reactions are determined. Comparison of the kinetics of the title reactions with the linear k_obs vs. [NH] plots found in the same aminolysis of O‐ethyl 4‐nitrophenyl dithiocarbonate (2) in the same solvent shows that the rate coefficient for leaving group expulsion from T^± (k₂) is larger for 2 due to a stronger push by EtO than PhO. The k₃ value is the same for both reactions since both proton transfers are diffusion controlled. Comparison of the title reactions with the same aminolysis of phenyl 4‐nitrophenyl thionocarbonate (3) in water indicates that (i) the k₂ value is larger for the aminolysis of 1 due to the less basic nucleofuge involved and the small solvent effect on k₂, (ii) the k₃ value is smaller for the reactions of 1 due to the more viscous solvent, (iii) the rate coefficient for amine expulsion from T^± (k₋₁) is larger for the aminolysis of 1 than that of 3 due to a solvent effect, and (iv) the value of the rate coefficient for amine attack (k₁) is smaller for the aminolysis of 1 in aqueous ethanol, which can be explained by a predominant solvent effect relative to the electron‐withdrawing effect from the nucleofuge. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 839–845, 1999     

Triazabicyclodecene: an effective isotope exchange catalyst in CDCl(3)

We describe the first effective H/D exchange reaction with acidic substrates in CDCl(3) at room temperature. The particularly mild reaction conditions involved (solvent, base, and temperature) allow the chemoselective deuteration of ketones over esters. An NMR study was conducted with the aim of rationalizing the results obtained in the presence of TBD as catalyst.     

Triazabicyclodecene: a simple bifunctional organocatalyst for acyl transfer and ring-opening polymerization of cyclic esters

1,5,7-Triazabicyclo[4.4.0]dec-5-ene (TBD) is an effective organocatalyst for acyl transfer as well as the ring-opening polymerization of cyclic esters. Its high activity is attributed to its ability to simultaneously activate both esters and alcohols, as demonstrated in a model reaction. This unique mechanism makes TBD a remarkably simple example of a bifunctional catalyst. The simplicity of the reaction conditions, the ready commercial availability of the catalyst, and its high activity provide an accessible methodology to allow future studies of tailor-made polyesters.     

Multicomponent reactions and supramolecular catalyst: A perfect synergy for eco-compatible synthesis of pyrido[2,3-d]pyrimidines in water

In this article, we have developed a straightforward, easy and exceedingly competent approach for the synthesis of 5-phenyl-5,6-dihydropyrido[2,3-d]pyrimidine-2,4,7(1H,3H,8H)-triones obtain in superior yields in a sole reaction pace with an air and humidity steady catalyst in water as a green solvent at 100^°C. The present procedure paves the approach for the synthesis of biologically fascinating molecular frameworks and has reward in conditions of little catalyst loading with palpable ambiguous and straightforward-to-do reaction circumstances with easy purification process. The used β-cyclodextrin catalyst was recuperated and repeated several times devoid of noteworthy loss of catalytic activity, which is a crucial parameter of green synthesis.     

Synthesis of polyamide-imide by blocked-methylene diisocyanates

The synthesis of polyamide-imide (PAI) can be performed by the reaction of p-chlorophenol-(PCP) blocked 4,4′-diphenyl methane diisocyanates (BMDI) with trimellitic anhydride (TMA) using a two-stage heating. At 80°C the polyimide oligomers were first formed and the high molecular weight PAI can not be available until the temperature was increased to 120°C and stayed for 3 h, during which the amide groups were formed and the molecular weight was increased. The molecular weights of the synthesized PAIs on various conditions were analyzed by measuring the intrinsic viscosity, amide/imide ratio from IR spectra, and average chain length from GPC. The best reaction conditions for obtaining a high molecular weight PAI by the solution polymerization are: (a) using N-methyl pyrollidone (NMP) as solvent, (b) adding more BMDI/TMA ratio, and (c) adding tert-n-butyl amine as the catalyst for the dissociation of blocked MDI and controlling the catalyst concentration at 0.162M. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 1711–1717, 1997     

Lipase-Catalyzed Synthesis of Carboxylic Amides: Nitrogen Nucleophiles as Acyl Acceptor

Summary.  The lipase-catalyzed aminolysis of carboxylic esters is a fairly general reaction that has been performed with a wide range of esters and amines, generally in anhydrous organic media to avoid undesirable hydrolysis of the ester. Alternatively, carboxylic amides can be synthesized by lipase mediated condensation of carboxylic acids and amines if an excess of either reactant is avoided. Chiral carboxylic esters have been resolved by lipase-catalyzed aminolysis. In the majority of these resolutions, Candida antarctica lipase B has been employed as the catalyst. A range of chiral amines has been resolved by lipase mediated acylation, using mainly the lipases from C. antarctica (B type) and Pseudomonas species. The enantiorecognition was frequently found to depend critically on the acylating agent and the reaction medium. Received December 20, 1999. Accepted January 1, 2000     

Highly Regioselective 5-endo-tet Cyclization of 3,4-Epoxy Amines into 3-Hydroxypyrrolidines Catalyzed by La(OTf)3

Highly regioselective intramolecular aminolysis of 3,4-epoxy amines has been achieved. Key features of this reaction are (1) chemoselective activation of epoxides in the presence of unprotected aliphatic amines in the same molecules by a La(OTf)₃ catalyst and (2) excellent regioselectivity for anti-Baldwin 5-endo-tet cyclization. This reaction affords 3-hydroxy-2-alkylpyrrolidines stereospecifically in high yields. DFT calculations revealed that the regioselectivity might be attributed to distortion energies of epoxy amine substrates. The use of this reaction was demonstrated by the first enantioselective synthesis of an antispasmodic agent prifinium bromide.     

Magnesium Bromide and Magnesium Chloride Hexahydrate Catalyzed One‐Pot Synthesis of Dihydropyrimidines via Biginelli Reaction under Solvent‐Free Conditions

Biologically important 12 new important 3,4‐dihydropyrimidin‐2‐(1H)‐ones (‐thiones) were synthesized with in one‐pot three‐component Biginelli reaction from the corresponding aromatic aldehydes (5‐methyl‐2‐thiophenecarboxaldehyde and 2‐chloro‐5‐nitrobenzaldehyde), β‐keto esters (ethylacetoacetate, allylacetoacetate, and t‐butylacetoacetate), and urea/thiourea in the presence of catalytic amount of magnesium bromide and magnesium chloride hexahydrate as nontoxic, inexpensive, and easily available catalysts under solvent‐free conditions at 80 and 100°C. Compared with the catalyst‐free three‐component Biginelli reaction conditions, this method consistently has the advantage of short reaction time (45–100 min) and good to excellent yields (75–91%).