Presence Of AIBN Research Articles

Synthesis of styrene, phenyl acrylate and allyloxyphenyl-functionalized porphyrins, and preliminary exploration of their utility for assembling multiple porphyrin units

Three free-base and two Zn(II) porphyrins carrying one alkene-substituted meso-aryl group and three solubilizing pentyl groups were prepared via mixed aldehyde-type syntheses. A meso [Formula: see text]-allyloxyphenyl porphyrin was obtained via the corresponding 5-([Formula: see text]-allyloxyphenyl) dipyrromethane. The porphyrins were fully characterized using a combination of NMR spectroscopy, high-resolution mass spectrometry, and UV-Vis absorption and emission spectroscopies. Two of the free-base porphyrins were heated in the presence of AIBN or benzoyl peroxide as the initiator. The major isolated products of these reactions contained two porphyrin units based on the results of MALDI-MS and 1H NMR analysis data, which was supported by the results of FTIR, UV-Vis absorption and emission spectroscopies, and gel permeation and liquid chromatographies. Additionally, the acrylamide-functionalized porphyrin could be attached to a polylysine scaffold under basic conditions. These results suggest that the olefinic handle can be used to assemble structures containing multiple porphyrinic macrocycles.

Pore Structure Tuning of Poly-EGDMA Biomedical Material by Varying the O-Quinone Photoinitiator.

Porous polymer monoliths with thicknesses of 2 and 4 mm were obtained via polymerization of ethylene glycol dimethacrylate (EGDMA) under the influence visible-light irradiation in the presence of a 70 wt% 1-butanol porogenic agent and o-quinone photoinitiators. The o-quinones used were: 3,5-di-tret-butyl-benzoquinone-1,2 (35Q), 3,6-di-tret-butyl-benzoquinone-1,2 (36Q), camphorquinone (CQ), and 9,10-phenanthrenequinone (PQ). Porous monoliths were also synthesized from the same mixture but using 2,2'-azo-bis(iso-butyronitrile) (AIBN) at 100 °C instead o-quinones. According to the results of scanning electron microscopy, all the resulting samples were conglomerates of spherical, polymeric particles with pores between them. Use of mercury porometry showed that the interconnected pore systems of all the polymers were open. The average pore size, Dmod, in such polymers strongly depended on both the nature of the initiator and the method of initiation of polymerization. For polymers obtained in the presence of AIBN, the Dmod value was as low as 0.8 μm. For polymers obtained via photoinitiation in the presence of 36Q, 35Q, CQ, and PQ, the Dmod values were significantly greater, i.e., 9.9, 6.4, 3.6, and 3.7 μm, respectively. The compressive strength and Young's modulus of the porous monoliths increased symbatically in the series PQ < CQ < 36Q < 35Q < AIBN with decreasing proportions of large pores (over 12 μm) in their polymer structures. The photopolymerization rate of the EGDMA and 1-butanol, 30:70 wt% mixture was maximal for PQ and minimal for 35Q. All polymers tested were non-cytotoxic. Based on the data from MTT testing, it can be noted that the polymers obtained via photoinitiation were characterized by their positive effect on the proliferative activity of human dermal fibroblasts. This makes them promising osteoplastic materials for clinical trials.

Serendipitous late-stage modification of dipeptide by using AIBN and thioacetic acid

Post-assembly peptide modifications have become an integral part of medicinal chemistry nowadays. This exercise is useful in finding novel bioconjugates, therapeutic peptides and protein labelling. Therefore, in our attempts towards the modification of peptides, we have tried to insert thiophene moiety in dipropargyl dipeptide in the presence of AIBN and thioacetic acid. Surprisingly, instead of thiophene group introduction, we observe the serendipitous functionalization of amide group i.e. –NHCOCH3 is converted into –NHCHO group.

Recent Advances on Radical-Mediated Cyanoalkylation/Cyanation using AIBN and Analogues as the Radical Sources

AbstractAIBN (2,2′-azobisisobutyronitrile) and analogues are readily available chemical reagents that are widely used as free-radical initiators of polymer chemistry. Importantly, AIBN and derivatives are also safe and efficient (alkyl)cyano sources for synthesizing cyano-containing scaffolds. In the past decades, synthetic strategies using AIBN and derivatives as radical sources have attracted increasing attention from the synthetic community. This review will provide a valuable tool for understanding the importance of AIBN and derivatives in the area of synthetic chemistry. In this context, we present a comprehensive review that guides readers through the developments in AIBN chemistry over the past five years from several aspects.1 Introduction2 Radical Addition onto Alkenes or Alkynes using AIBN as Cyanoalkyl Radical3 Dehydrogenated, decarboxylated cyano-alkylation by using AIBN and analogues4 Synthesis of Ketone and its Derivatives with AIBN and Analogues as Carbonyl Source5 Construction of Multi-ring Skeletons in the Presence of AIBN and Analogues6 Direct Application as Cyano (CN) Source in Cyanation Reactions7 Conclusions

Radical Reactions of Vinyl Triflates and its Derivatives

Vinyl triflates are valuable precursors for vinyl cations, vinyl carbenes, and electrophiles for transition-metal-catalyzed cross-coupling reactions. However, in these reactions, the trifluoromethyl group is not installed in the final products. The radical reactions of vinyl triflates were limited until our beginning. We initially achieved the synthesis of α-trifluoromethylated ketones from vinyl triflates using triethyl borane as a radical initiator. Since the reaction proceeds chemoselectivity toward the conjugated vinyl triflates, we achieved the chemo- and regio-selective trifluoromethylation of 1,3-bis(vinyl triflates). We developed one-pot trifluoromethylation from aryl alkynes with perfluoroalkanesulfonic acids in the presence of AIBN as a radical initiator. In addition, a crossover experiment and DFT calculations support that the reaction proceeds through an intermolecular pathway. The radical reaction of vinyl triflates in the presence of alkenes afforded γ-trifluoromethylated ketones. We also developed a one-pot triflation-trifluoromethylation-triflation of imines leading trifluoromethyl-substituted vinyl trifluoromethanesulfonic amides.

Thermal degradation behavior of maleimide-methacrylate copolymers bearing pendant allyl groups

Maleimide copolymers bearing pendant allyl groups were obtained by radical copolymerization of maleimide and allylmaleimide with methylmethacrylate and allylmethacrylate in bulk and methanol solution in the presence of AIBN. The structural features of the copolymers were studied using UV, IR, and NMR spectroscopy. During the copolymerization of maleimide with allylmethacrylate and N-allylmaleimide with methylmethacrylate at high conversions, an increase in the viscosity of the system is observed, which results in cross-linking along the “allyl bonds” of side polymer chains with the formation of insoluble copolymers that swell in DMSO. Copolymerization of N-allylmaleimide with allylmethacrylate already at initial conversions leads to the formation of crosslinked copolymers with high heat resistance. The thermal degradation behavior of copolymers was studied and the volatile products were investigated.

Graft hyper-branched dendrimer onto WS2 nanosheets modified Poly (N-Vinylcaprolactam) as a thermosensitive nanocarrier for Pioglitazone delivery using near-infrared radiation

In this paper, graft-copolymerization of N-vinylcaprolactam and allylamine onto tungsten disulfide (WS2) in the presence of AIBN as initiator has been carried out to prepare the WS2@ (NVCL-co-AAm). Subsequent fifth-generation dendrimer was attached to their surface, and used as a nanocarrier for the pioglitazone (PG) drug delivery. The resulting polymer was characterized by FTIR, XRD, TEM, EDX, and TGA. We loaded PG onto polymer and evaluated the drug loading and release patterns in simulated human blood fluid (pH 7.4) for the treatment of diabetes in vitro. The thermosensitive nanocarrier indicated a maximum of 98 % PG release in the simulated human blood fluid at 50 °C within 6 h, and about 18 % of total PG was released from the nanocarrier within 6 h at 37 °C. Herein, we studied near-infrared (NIR) radiation as an irritant for inducing PG release from nanocarrier. Also, PG releasing was 100 % under NIR laser irradiation within 15 min, which was roughly four times of that without laser irradiation. NIR laser light heated the nanocarrier, causing shrinkage of the polymer, which increased the penetrability of the membrane and resulted in PG release. Following four adsorption isotherm models, the Langmuir model excellently explained the adsorption isotherm.

A computational study of the reaction mechanism of 2,2-azobis(isobutyronitrile)-initiated oxidative cleavage of geminal alkenes.

A computational study of 2,2-azobis(isobutyronitrile) (AIBN)-initiated aerobic oxidative cleavage of alkenes is carried out employing density functional theory (DFT) and high-level coupled-cluster methods, such as coupled-cluster singles and doubles with perturbative triples [CCSD(T)]. Our computations show that the barriers for the formation of dioxetane derivatives suggested by Xu and co-workers (J. Org. Chem., 2014, 79, 7220-7225) for the reaction mechanism of aerobic oxidative cleavage of alkenes are computed to be higher than 65 kcal mol-1. This barrier is relatively high under the reaction conditions. Our results for the Xu mechanism indicate that the reaction does not proceed via the formation of a dioxetane ring under the reaction conditions. Our results demonstrate that the reaction of aerobic oxidative cleavage of geminal alkenes in the presence of AIBN is initiated by the peroxyl radical 9, contrary to the isobutyronitrile radical 2. Our results show that the 2-(2-hydroxyl-1,1-diarylethoxy)-2-methylpropanenitrile radical (15) does not appear throughout the reaction scheme and the reaction progresses over the 2-(2-hydroxyl-2,2-diarylethoxy)-2-methylpropanenitrile radical (13) rather than the 2-(2-hydroxyl-1,1-diarylethoxy)-2-methylpropanenitrile radical (15). Our results are in agreement with the experimental results for the aerobic oxidative cleavage of the geminal disubstituted alkenes. Our results also demonstrate that the epoxide derivatives can be formed as an intermediate under the reaction conditions. This reaction is not applicable for pyridine derivatives due to the conversion of vinylpyridine derivatives to N-oxide derivatives.

Effects on the Physical Properties of Ophthalmic Hydrogels Containing 4-Chlorostyrene and Cerium Oxide Nanoparticles with Ultraviolet Blocking Ability.

The optical, physical and polymerization property of hydrogel ophthalmic lenses made by cerium nanoparticles containing 4-chlorostyrene as a base hydrogel material were analyzed. Cerium oxide nanoparticles were used as additive. And HEMA, 4-chlorostyrene and a cross-linker EGDMA were copolymerized in the presence of AIBN as an initiator. Also, the polymerization property such as TGA and absorbance of the prepared lens were measured. Measurement of the polymerization characteristics of the copolymerized material showed that TGA was found that the addition of cerium oxide increased thermal stability. The physical properties of the basic lenses were totally satisfied and breaking strength gradually increased with the addition amount of 4-Chlorostyrene. Cerium nanoparticles are considered to satisfy the basic requirements of hydrogel lenses and UV-blocking amount gradually increased according to the addition ratio of cerium oxide nanoparticles without affecting the basic physical properties. Therefore, these materials can be used effectively as additives for ophthalmic hydrogel lenses.

Radical Copolymerization of N-Substituted 2-Azanorborn-5-enes with N-Vinylpyrrolidone

The radical copolymerization of N-methyl-2-azanorborn-5-ene, N-benzyl-2-azanorborn-5-ene, N-allyl-2-azanorborn-5-ene, and N-(2-azanorborn-5-en-2-yl)methyl acetate with N-vinylpyrrolidone is carried out in bulk in the presence of AIBN as an initiator. It is shown that the copolymerization yields statistical copolymers enriched in N-vinylpyrrolidone units. It is demonstrated that the rate of copolymerization decreases with increasing fraction of azanorbornene in the initial monomer mixture. Using 13С NMR spectroscopy, it is found that the copolymerization of azanorbornenes with N-vinylpyrrolidone occurs via the double bond of the norbornene ring. The allyl group of N-allyl-2-azanorborn-5-ene is uninvolved in copolymerization at both the equimolar comonomer ratio and the double excess of N-vinylpyrrolidone.

Bis-N,N-aminophosphine (PNP) crosslinked poly(p-tert-butyl styrene) particles: A new support for heterogeneous palladium catalysts for Suzuki coupling reactions

Crosslinked polymer particles carrying hemilabile bis-N,N-aminophosphine (PNP) moieties are obtained by the copolymerization of a PNP-derived monomer bearing four vinyl fragments as cross-linkers, with para-tert-butylstyrene and divinylbenzene, using free radical copolymerization in presence of AIBN, performed in aqueous dispersed medium. This new support was characterized by thermogravimetric analysis, elemental analysis, laser diffraction, solid state NMR. The PNP moiety could allow monochelation to palladium. The resulting insoluble Pd-catalyst revealed to be very active for Suzuki cross-coupling with several substrates, allowing separation of the product from the catalyst by filtration. The final palladium PS-PNP catalyst could be reused for several catalytic cycles.

The investigation of butyl acrylate grafting using model alkyds

Four model alkyds (stearic, oleic, linoleic, and linolenic model alkyds) were copolymerized with butyl acrylate (BA) in the presence of AIBN or BPO. 1H and 2D gHMQC NMR, Soxhlet extraction, and gas chromatography were used to characterize model alkyd–BA systems. It was found that mechanisms of grafting BA onto model alkyds were dependent on the structure of fatty acids in the model alkyds. In stearic model alkyd hybrid systems, BA homopolymer was the predominate pathway with minimal grafting via hydrogen abstraction from polyol backbone followed by termination with propagating BA radicals. Oleic model alkyd–BA systems improved the degree of grafting by direct addition of the BA free radical to the double bonds. Severe retardation of BA polymerization was observed in both linoleic and linolenic model alkyd–BA systems due to the presence of double allylic sites. A chain transfer process subsequently dominates the other free radical pathways leading to a high degree of grafting.

Studies on twist bent core zinc (II) methacrylate supramolecular columnar hexagonal phase mesogen derived from azobenzene moiety and its photo luminescent behaviours

A class of Zn(II) polymethacrylate mesogen was tailored with photoluminescent property as well as high thermal stability by wrapping the Zn(II) metal in polymethacrylate mesogenic core. The versatile thermal stability of the mesophase was accounted by long chain terminal alkoxy groups and jacketed Zn(II) metal core. The extended stable mesophase with rise in temperature was achieved by excellent coordination between the supramolecular ligand with that of metal core. The Schiff base was prepared by treating (1-bromo (4-dodecyloxy azobenzene)) with octadecyl amine in ethanolic medium. The Schiff base obtained was polymerised with methacrylic acid (MA) in presence of AIBN as free radical initiator. The supramolecular mesogenic ligand (PMA-L) was further complexed with Zn(II) acetate in 1:1 M ratio. The Zn(II) supramolecular mesogen was extensively characterized by 1H NMR, 13C NMR and FT-IR. The mesomorphic behaviour was studied by XRD diffractogram, DSC, POM. The Zn(II) supramolecular exhibits columnar phase transition due the molecular stacking in disc shape. The disc shape mesophase of the Zn(II) supramolecular mesogen was achieved by sandwich pattern of metal core between two organic ligands arrangement. The photo physical character of the Zn(II)polymeric mesogen was studied by absorption and fluorescence spectral method.

Study on the Wettability of Ophthalmic Hydrogel Lens Containing Graphene Oxide Nanoparticles with Wettability Measurement Method.

For manufacturing ophthalmic lens, HEMA, PVP, Bis-GMA, GO nanoparticles and EGDMA (ethyleneglycol dimethacrylate) were copolymerized in the presence of AIBN as an initiator. After polymerization, the physical properties such as water content, refractive index, contact angle of produced hydrogel lenses were measured. As a result, when GO nanoparticles were added to the Ref. and Ref.-B samples, the wettability increased due to the hydrogen bonding between the GO and the water molecules, which were distributed on the surface. In the case of Ref.-P containing PVP, the probability of hydrogen bonding with the water molecules on the surface was lowered as hydrogen bonding was induced by the nitrogen of PVP and the carboxyl group of the GO nanoparticles; thus, the wettability somewhat decreased. Therefore, GO, which has excellent abrasion resistance, is considered useful as a material for ophthalmic lenses with excellent wettability and strength when added to the general hydrogel lens materials other than hydrophilic materials like PVP.

Poly[4-pyridinyl-4´-(2-methacryloyloxyethoxy)styryl ketone-co-2-hydroxypropyl methacrylate]: Synthesis, Characterization, Thermal and Electrical properties, and Photocrosslinking behavior

Synthesis of a chalcone bearing pyridine ring, 4-pyridinyl-4´-(2-hydroxyethoxy)styryl ketone, was carried out from the reaction of 4-acetyl pyridine and 4-(2-hydroxyetoxy)benzaldehyde in an aqueous solution of NaOH. 4-Pyridinyl-4´-(2-methacryloyloxyethoxy)styryl ketone which is the methacrylate monomer bearing chalcone structure in side chain, was obtained from acylation of 4-pyridinyl-4´-(2-hydroxyethoxy)styryl ketone with methacryloyl chloride in the cold. The copolymer of 4-pyridinyl-4´-(2-methacryloyloxyethoxy)styryl ketone and 2-hydroxypropyl methacrylate was prepared by free radical polymerization in presence of AIBN at 70 oC. FTIR, 1H-NMR and 13C-APT spectroscopic techniques were used for structural characterization of the Chalcone, the monomer and the copolymer. Thermal characterization of the copolymer was carried out using DSC and TGA techniques. DSC curve shows that this copolymer has a glass transition temperature of 78 oC. The TGA curve shows that decomposition given volatile product started at 230 °C and a residue of 21% left at 500 °C. Dielectric constant (ε´) of the copolymer decreased rapidly from 8.8 to 4.2 with increasing frequency in the range of 100-1000 Hz, and after this frequency ε´ quantity remained constant at a value such as 4.2. ε´ Value of the copolymer increased only from 4.2 to 4.9 with increasing from 290 K to 385 K. The AC conductivity of the copolymer increases from 5.01x10-10 S/cm to 126.0x10-10 S/cm as the frequency increase from 100 Hz to 5000 Hz. The AC conductivity increases slightly with increasing temperature, 2.52x10-9 S/cm at 300 K, and 2.89x10-9 S/cm at 385 K. After a solution of the copolymer was irradiated using UV light at 365 nm at room temperature, the absorption band at 356 nm disappeared and a new band was seen at 284 nm.

New (aminomethyl)phosphines via selective hydrophosphination and/or phosphorus based Mannich condensation reactions

Controlled stepwise reaction of a geminal substituted alkene or primary amine group afforded a small library of new functionalised tertiary and ditertiary phosphines. Accordingly, Mannich based condensation of the commercially available disubstituted arene C6H4(NH2){2-C(Me)=CH2} with HOCH2PR2 (R2 = Cg: 1,3,5,7-tetramethyl-2,4,8-trioxa-6-phosphaadamantyl; Ph2) afforded the (aminomethyl)phosphines C6H4(NHCH2PCg){2-C(Me)=CH2} L1 and C6H4(NHCH2PPh2){2-C(Me)=CH2} L2 in approx. 60% yield. In addition to the formation of L2, the diphosphine L3 was also identified and independently synthesised upon reaction of C6H4(NH2){2-C(Me)=CH2} with two equiv. of HOCH2PPh2 in CH3OH under reflux. Alternatively, reaction of C6H4(NH2){2-C(Me)=CH2} with H-PR2 (R2 = Cg or Ph2) in the presence of AIBN [2,2′-azobis(2-methylpropionitrile)] as free radical initiator, afforded the primary amine functionalised phosphines C6H4(NH2){2-CH(Me)CH2PCg} L4 and C6H4(NH2){2-CH(Me)CH2PPh2} L5 in 85% and 66% isolated yields respectively. In both cases only the anti-Markovnikov addition products were observed. Subsequent reaction of L5 with HOCH2PR2 (R2 = Ph2) afforded the unsymmetrical ditertiary phosphine C6H4(NHCH2PPh2){2-CH(Me)CH2PPh2} L6. Some preliminary coordination studies towards [RuCl(μ-Cl)(η6-C10H14)]2, [AuCl(tht)] (tht = tetrahydrothiophene) and [MCl2(η4-cod)] (M = Pd, Pt; cod = cycloocta-1,5-diene) demonstrate these new ligands behave as classic P-donors leaving the pendant amino or alkenyl groups non-coordinating. All compounds have been characterised by multinuclear NMR, FT−IR, mass spectrometry and microanalysis. Single crystal X-ray studies have been performed on L3, L5, L6, 1, 3b·0.5CH2Cl2, 4a·1.5CH2Cl2, 5 and 6·0.5CDCl3·0.5C4H10O.

Oxidative Recyclization of 1H-Indoles for Synthesis of 2-Indolylbenzoxazinones via Cleavage of the C2-C3 Bond with AIBN under Air.

A novel and concise method for the oxidation of unprotected indole derivatives to synthesize 2-indolylbenzoxazinones in the presence of AIBN under open air has been successfully demonstrated. This metal-free reaction is both atom- and step-efficient and is applicable to a broad scope of substrates. This new methodology provides a facile pathway for oxidative C2-C3 bond cleavage and recyclization of 1H-indoles.

Free Radical Polymerization Behavior of the Vinyl Monomers from Plant Oil Triglycerides

A one-step method of plant oil direct transesterification was used to synthesize new vinyl monomers from sunflower (SFM), linseed (LSM), soybean (SBM), and olive (OVM) oils. The degree of unsaturation in plant oil fatty acids was used as a criterion to compare the free radical polymerization behavior of new monomers. The number-average molecular weight of plant oil-based homopolymers synthesized in toluene in the presence of AIBN at 75 °C varies at 11 000–25 000 and decreases as follows: poly(OVM) > poly(SFM) > poly(SBM) > poly(LSM), corresponding to increasing degree of unsaturation in the monomers. Rate of polymerization depends noticeably on the degree of unsaturation in monomers. Due to the allylic termination, chain propagation coexists with effective chain transfer during polymerization. The obtained values of CM (ratio of chain transfer and propagation rate constants) depends on monomer structure as follows: CM(LSM) > CM(SBM) > CM(SFM) > CM(OVM). 1H NMR spectroscopy shows that the fraction of the r...

N-Hydroxyphthalimide Immobilized on Poly(HEA-co-DVB) as Catalyst for Aerobic Oxidation Processes

In the present study, poly(HEA-co-DVB) was synthesized (loading of OH groups: 8.07 mmol OH/g, crosslinking degree: 6 % DVB) and used for N-hydroxyphthalimide (NHPI) immobilization via ester bond (NHPI loading: 2.06 mmol NHPI/g). The obtained polymeric support and poly(HEA-co-DVB)/NHPI catalyst were characterized by FT-IR and XPS spectroscopy, elemental analysis, thermogravimetry and particle size measurement. The novel polymer-supported NHPI catalyst was tested in aerobic oxidation of p-methoxytoluene and α-methylstyrene. The studied reactions were carried out in the presence of AIBN and/or Co(II) salt without solvent or in acetic acid as solvent. It was found that the obtained polymer-supported NHPI catalyst showed the best catalytic performance, which was attributed to a high content of accessible NHPI moieties. The recovery and recycling of the obtained HEA/DVB-NHPI was only possible in reactions proceeded in solvent-free conditions.

Synthesis, thermal degradation and dielectric properties of poly[2-hydroxy,3-(1-naphthyloxy)propyl methacrylate

2-Hydroxy-3-(1-naphthyloxy)propyl methacrylate (NOPMA) monomer was synthesized from reaction of 2-[(2-naphthyloxy)methyl]oxirane with methacrylic acid in the presence of pyridine. The polymerization of NOPMA was carried out by free radical polymerization method in the presence of AIBN at 60 °C. The structure of monomer and polymer was characterized by 1H-NMR, 13C-NMR and FT-IR spectroscopy techniques. The glass transition temperature and average-molecular weights of poly(NOPMA) were measured using differential scanning calorimetry and gel permeation chromatography, respectively. The thermal degradation behavior of poly(NOPMA) has been investigated by FT-IR studies of the partially degraded polymer and thermogravimetry. The cold ring fractions (CRFs) were collected at two different temperatures, initially fraction-1 (CRF1) is from room temperature to 320 °C, and the other fraction-2 (CRF2) is from 320 to 500 °C. The volatile products of the degradation were trapped at −195 °C (in liquid nitrogen). All the fractions were characterized by FT-IR, 1H and 13C-NMR spectroscopic techniques, and the cold ring fractions (CRFs) were also characterized by GC–MS. For the degradation of polymer, the major compound between products of CRFs is α-naphthol. The GC–MS, FT-IR and NMR data showed that depolymerization corresponding to monomer was not prominent below 320 °C in the thermal degradation of poly(NOPMA). The mode of thermal degradation containing formation of the major products was identified. The dielectric permittivity (ε′), the loss factor (ε″) and conductivity (σac) were measured using a dielectric analyzer in the frequency range of 50 Hz to 20 kHz.