Presence Of AIBN Research Articles

Synthesis and Polymerization of Novel Quinone Methide Ketals

Novel quinone methide ketals, 8-[ 1'-cyano-1'-(ethoxycarbonyl)methylene]-l,4-dioxaspiro[4.5]deca-6,9-diene (1a) and 8-(1',l'-dicyanomethy1ene)-1,4-dioxaspiro[4.5]deca-6,9-diene (1b), were synthesized, and their polymerization behavior was investigated. Polymerizations of 1a and 1b initiated with BPO and BF3·Et2O gave corresponding novel ring-opening polymers, but no polymerization with BuLi. Copolymerization of 1a with St in the presence of AIBN at 60 °C gave the monomer reactivity ratios r1(1a) = 0.50 ± 0.1 and r2(St) = 0.1 ± 0.02, and Q and e values of 1a were 2.46 and +0.93, indicating that 1a is a highly conjugative, electron-accepting monomer. Homopolymers of 1a and 1b had better thermal stability than that of 7-cyano-7-(ethoxycarbonyl)- 1,4-benzoquinone methide.

Radical Cyclization in Heterocycle Synthesis. Part 13. Sulfanyl Radical Addition—Cyclization of Oxime Ethers and Hydrazones Connected with Alkenes for Synthesis of Cyclic β‐Amino Acids.

Abstract A combination of sulfanyl radical addition–cyclization of the oxime ethers and hydrazones connected with alkenes and subsequent conversion of a phenylsulfanylmethyl group to a carboxyl group provides a novel method for the construction of the cyclic β-amino acids. Upon treatment with thiophenol in the presence of AIBN, the oxime ethers and hydrazones smoothly underwent sulfanyl radical addition-cyclization to give the 2-(phenylsulfanylmethyl)cycloalkylamine. This method was successfully applied to the practical synthesis of 2-aminocyclopentanecarboxylic acid and 4-amino-3-pyrrolidinecarboxylic acid.

Half-sandwich molybdenum(III) compounds containing diazadiene ligands and their use in the controlled radical polymerization of styrene

The reaction of CpMoCl 2 with diazadiene ligands RNCHCHNR (R 2dad) affords the corresponding paramagnetic complexes CpMoCl 2(R 2dad) (R=Ph, 1; p-Tol, 2; C 6H 3Pr 2 i -2,6, 3; and Pr i , 4). All compounds have been characterized by EPR spectroscopy and have been investigated by cyclic voltammetry. They display one-electron oxidation and reduction processes, these being reversible or irreversible depending on the nature of R. The irreversibility of the reduction wave is due to a chemical follow-up process which consists of chloride loss from the reduced product. This phenomenon is suppressed in the presence of excess chloride in solution. An X-ray structure of 3 verifies the mononuclear nature of the compound and the chelating mode of the dad ligand, the MoN 2C 2 ring being essentially planar. The NC and CC bond distance pattern suggests the important contribution of an enediamido Mo(V) limiting form. In the presence of 1-bromoethylbenzene, complexes 1– 4 catalyze the controlled/‘living’ radical polymerization of styrene. Complex 3 also leads to a controlled/‘living’ radical polymerization of styrene in the presence of AIBN (α,α-azoisobutyronitrile) as a radical generator. Therefore, this is the second example of a compound which is capable of controlling the styrene radical polymerization under both ATRP and SFRP conditions.

Thermal behaviour of dendritic methacrylated polyesters

A dendritic polyester based on pentaerythritol and 1,2,4—benzenetricarboxylic acid anhydride followed by modification with glycidyl methacrylate was synthesised by using a divergent approach. The dendrimer (D-2) thus obtained had approximately eight double bonds. Several blends of D-2 with varying proportions of bismethacryloxy derivative of diglycidyl ether of bisphenol-A having styrene as a reactive diluent (VE resin) were prepared. The Brookfield viscosity of VE resin increased with an increase in D-2 content in the blends.Curing behaviour of these resins in the presence of AIBN was investigated by DSC. No significant change in curing exotherm was observed by addition of D-2 to the VE resin. Isothermal curing of resin samples in the presence of AIBN was done at 60 °C for 5 h and then at 150 °C for 90 mins. A significant improvement in char yield at 600 °C in nitrogen atmosphere was observed in samples containing D-2.Mechanical properties of glass fiber reinforced laminates with 31 ± 3% of resin content (w/w) were also determined. Smoke density of laminates increased with decrease in D-2 content in the resin, whereas only a marginal effect on limiting oxygen index was observed.

Radical cyclization in heterocycle synthesis. Part 13: Sulfanyl radical addition–cyclization of oxime ethers and hydrazones connected with alkenes for synthesis of cyclic β-amino acids

A combination of sulfanyl radical addition–cyclization of the oxime ethers and hydrazones connected with alkenes and subsequent conversion of a phenylsulfanylmethyl group to a carboxyl group provides a novel method for the construction of the cyclic β-amino acids. Upon treatment with thiophenol in the presence of AIBN, the oxime ethers and hydrazones smoothly underwent sulfanyl radical addition-cyclization to give the 2-(phenylsulfanylmethyl)cycloalkylamine. This method was successfully applied to the practical synthesis of 2-aminocyclopentanecarboxylic acid and 4-amino-3-pyrrolidinecarboxylic acid.

Polymerization and characterization of acrylonitrile with γ‐methacryloxypropyltrimethoxy‐silane grafted bentonite clay

AbstractNovel natural clay–polymer hybrid materials are prepared from natural bentonite that was modified with silane‐coupling agent, γ‐methacryloxypropyltrimethoxysilane (A‐174), and acrylonitrile. By changing the molar ratio of acrylonitrile in the initial monomer feed, several clay–hybrid materials were prepared. The structure and thermal stability of hybrid materials were investigated by various methods. The A‐174‐modified bentonite was dispersed in a solution of acrylonitrile in toluene. In this system, radical polymerization in the presence of AIBN was carried out. Product formed at the particle surface was either physically bound by entanglement or chemically bound by covalent bonding to the silane. In this way, core–shell morphology was obtained with an inorganic core and a polymer shell. The results showed that bonding at the surface of bentonite took place by hydrolytic cleavage of methoxy groups of A‐174 with hydroxy groups of bentonite. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 164–171, 2002; DOI 10.1002/app.10289

Investigation of the thermal decomposition of poly(2-hydroxypropyl methacrylate)

2-Hydroxypropyl methacrylate (HPMA) was polymerized in the presence of AIBN at 60 °C. The thermal degradation behaviour of poly(HPMA) has been studied using thermogravimetry (TG), the IR examination of the partially degraded polymer, and a single line vacuum system consisting of a degradation tube, with a condenser for product collection and a gas phase IR cell. The cold ring fraction (CRF) was collected at two different temperatures, one of them (CRF1) is from ambient temperature to 340 °C and the other (CRF2) in the range 340–450 °C. The volatile products of the degradation were trapped at −196 °C (in liquid nitrogen). All fractions of the degradation were investigated by means of IR, 1H- and 13C-NMR techniques and the CRFs were also characterized by GC–MS. As major products of the degradation, the monomer, 2-propanal, methacrylic acid, 1,2-propandiol, 2-(2-propenyloxy)propyl methacrylate, 2-hydroxpropanal, and hydroxymethyl isopropyl ether were detected. Degradation mechanism and the origins of the identified products are discussed.

Homolytic carbostannylation of alkenes and alkynes with tributylstannyl enolates.

In the presence of AIBN, tributylstannyl enolates derived from aromatic ketones reacted with electron-deficient alkenes and a variety of alkynes to give the corresponding carbostannylated adducts. The reactions with methyl acrylate gave alpha-tributylstannylmethyl-gamma-ketoesters, unlike the known Michael-type reaction of stannyl enolates forming delta-ketoesters. The carbostannylation of alkynes proceeded in an anti addition mode to afford beta,gamma-unsaturated ketones. The reactivity of stannyl enolates as radical transfer agents could be utilized for radical cyclization of 1,6-enynes.

ChemInform Abstract: Radical Addition of p‐Toluenesulfonyl Bromide and p‐Toluenesulfonyl Iodide to Allenic Alcohols and Sulfonamides in the Presence of AIBN: Synthesis of Heterocyclic Compounds.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Synthesis of biaryls by intramolecular radical transfer in phosphinates.

Phosphinates 20a-35a give biaryls 20b-35b on heating with stannanes in the presence of AIBN. The process involves a radical ipso substitution on the migrating aryl ring.

RADICAL POLYMERIZATION OF METHYL METHACRYLATE WITH DIPHENYL DISELENIDE UNDER THERMAL OR PHOTOIRRADIATIONAL CONDITIONS

Polymerization of methyl methacrylate (MMA) with diphenyl diselenide (DPDSE) in the presence of AIBN at 60°C was investigated. DPDSE was worked as a chain transfer agent (CTA). The chain transfer constant (Ctr) of DPDSE for MMA was estimated to be 1.43. On the other hand, DPDSE was functioned as a photoiniferter for the photopolymerization of MMA. In a limited range of conversion, both the polymer yield and number average of molecular weight ([Mbar]n) increased with the reaction time, and the [Mbar]n linearly increased with the yield. The terminal structure of poly(MMA) was investigated by the 77Se NMR spectrum based on Methyl α-phenylseleno isobutylate (MSEPI) as model compound of the ω-chain end of poly(MMA). Further, photopolymerization of poly (MMA) containing phenylseleno group at ω-chain end as a polymeric photoiniferter with MMA effectively afforded a poly (MMA) having higher molecular weight.

Synthesis and lectin recognition of polystyrene core-glycopolymer corona nanospheres.

Polymeric nanospheres with a polystyrene core and a glucosyloxyethyl methacrylate (GEMA) oligomer corona were synthesized by the free radical coplymerization of styrene (M(1)) plus a GEMA macromonomer (M(2)) at various molar ratios (M(1)/M(2) = 50-150) in the presence of AIBN (1 mol % to the total monomer) in an ethanol/water (3/2, v/v) solvent. The size of the nanospheres was controlled from 300 to 620 nm by altering the monomer ratio. The size distributions were significantly narrow. The amount of glucose conjugated per unit surface area of the nanosphere, which was analyzed by the anthron-sulfuric acid method, was 1.01-2.28 microg cm(-1), which increased with an increase in size. The transmittance of a solution of dispersed nanospheres (the corresponding glucose concentration was 73 microM) increased by the addition of the glucose-binding protein concanavalin A (Con A) (1-50 microM), indicating that the nanospheres were being precipitated by the cross-linking of ConA. An enzyme-linked lectin assay (ELLA) revealed that Con A bound to the glucose on the nanospheres 250-700-fold more than to monomeric glucose. The binding activity to the nanospheres was less than that to a GEMA oligomer, and decreased with an increase in the amount of GEMA oligomer grafted onto the nanosphere, possibly because of steric hindrance of the lectin binding to the glucose on the nanospheres. The polystyrene core-glycopolymer corona nanosphere is a useful material for studying sugar-biomolecule recognition.

Radical addition of p-toluenesulfonyl bromide and p-toluenesulfonyl iodide to allenic alcohols and sulfonamides in the presence of AIBN: synthesis of heterocyclic compounds.

Radical addition of p-toluenesulfonyl bromide and p-toluenesulfonyl iodide to allenic alcohols and sulfonamides in the presence of AIBN: synthesis of heterocyclic compounds.

Synthesis of enantiopure mono- and disubstituted tetrahydroisoquinolines by 6- exo radical cyclizations

2-( o-Bromophenyl)-3-allyl- and 2-allyl-3-( o-bromobenzyl)-substituted perhydrobenzoxazines, derived from (−)-8-amino menthol, readily cyclized stereoselectively by reaction with tributyltin hydride in the presence of AIBN. The cyclization compounds were transformed into enantiopure 4-alkyl tetrahydroisoquinolines by reductive ring opening of the N,O-acetal moiety with lithium aluminum hydride. Enantiopure 1,4- and 3,4-dialkyl-substituted tetrahydroisoquinolines were also prepared by reaction of the cyclized compounds with methylmagnesium iodide and subsequent elimination of the menthol appendage.

Radical cyclization in heterocycle synthesis. 11.(1) A novel synthesis of alpha,beta-disubstituted gamma-lactones via sulfanyl radical addition-cyclization using hydroximates as a tether

A combination of sulfanyl radical addition-cyclization of dienes connected with hydroximates and subsequent conversion of the resulting cyclic hydroximate to the lactones provides a novel method for the construction of alpha,beta-disubstituted gamma-lactones. Upon treatment with thiophenol in the presence of AIBN, dienes connected with hydroximates smoothly underwent sulfanyl radical addition-cyclization to give cyclic cis- and trans-hydroximates. Hydrolysis of cyclic hydroximates gave the desired cis- and trans-lactones in high yield. This method was successfully applied to the practical synthesis of (+/-)-oxo-parabenzlactone.

The synthesis of poly(styrenechromiumtricarbonyl) in the presence of triisobutylboron

Poly(styrenechromiumtricarbonyl) was synthesized by radical homopolymerization of styrenechromiumtricarbonyl in AcOEt at 50 °C in the presence of AIBN and triisobutylboron.

Gold and platinum benzenehexathiolate complexes as large templates for the synthesis of 12-coordinate polyphosphine macrocycles

A general strategy for the synthesis of large-ring, poly-donor macrocycles using multi-metal ion templates is outlined. This strategy is illustrated in the design and synthesis of the hexanuclear (divinyl)(phenyl)phosphine gold complex of benzenehexathiolate, {[(C2H3)2(Ph)P]Au}6(C6S6) (1), which undergoes macrocycle formation upon reaction with PhPH2 in the presence of AIBN (Scheme 1). NMR spectra (1H and 31P) and elemental analyses indicate that the resulting macrocycle is a 36-membered ring containing 12 phosphorus donors, six of which are coordinated to the six Au atoms in the Au6(C6S6) core. A series of tri-platinum complexes, [(P∩P)Pt]3(C6S6) (16–19), where (P∩P) is a bidentate phosphine ligand, with three (P∩P)PtII units coordinated to a C6S66− core, were also prepared as models for templated formation of other poly-phosphorus macrocycles.

Polymerization of Methacrylates Containing Cationic Cyclopentadienyliron Moieties

A novel approach to the synthesis of polymethacrylates containing cationic cyclopentadienyliron moieties pendent to their side chains was accomplished via the use of π-coordinated organoiron complexes. The complexed methacrylates were polymerized in the presence of AIBN to give soluble organoiron polymethacrylates (6a and 6b, 10, 14a and 14b) in 80–90% yields. Photolytic demetallation of the organoiron polymers allowed for the isolation of their organic analogues (7a and 7b, 11, 15a and 15b) whose weight average molecular weights ranged from 48,500 to 68,300.

Homolytic allylation of vinyl iodides with allylstananes

In the presence of AIBN or Et 3B, a variety of vinyl iodides reacted with allylstannanes bearing an electron-withdrawing group at the β-position to afford 1,4-dienes in moderate to good yields. The allylation showed high stereoselectivity when the α-substituent of the iodides was a phenyl group, or the β-substituent was a bulky group.

Thiol radical addition to alkynes. Sulfanyl radical addition and hydrogen atom abstraction relative reaction rates

2-(Toluenesulfanyl)- 1 and 2-(benzenesulfanyl)-phenylacetylene 10 reacted with benzenethiol and toluenethiol, respectively, in the presence of AIBN at 84 and 154 °C to give products deriving from vinyl radicals 2 which undergo hydrogen abstraction reaction and 5- ortho and 5- exo cyclization onto both the adjacent phenyl rings in competition with the β-fragmentation. Definitive evidence has been obtained that alkanesulfanyl radical addition to the alkyne triple bond is a non-reversible process, whereas arenesulfanyl radicals add in a reversible mode. Competing experiments involving several alkynes towards benzenethiol and benzeneethanethiol radical addition have been performed in order to determine the relative rate constants of the sulfanyl radical addition to the alkyne triple bond (k 1) and the hydrogen abstraction reaction by the resulting vinyl radicals (k H). The k 1 values are mainly determined by the vinyl radical stabilization provided by the C-(α) vinyl radical substituent, whereas the k H values seem to be mainly determined by polarity factors. An unexpected different behavior between α-propyl and α-long-chain substituents is discussed in terms of different hybridization of the vinyl radical.