Diazapolycyclic compounds—XIVTetrahedron33, 2109 (1977).: Epoxides from diazaquinone adducts: synthesis and stereochemical characterization

Epoxidation by m-chloroperbenzoic acid of adducts obtained by Diels-Alder reaction of pyridazine-1,4-dione, phthalazine-1,4-dione and benzo(g)phthalazine-1,4-dione with substituted 1,3-butadienes is reported. Although the epoxidation takes place in most of the cases in good yields, no reaction is observed in adducts which lack electron-donating groups attached to the double bond, and their epoxides must be obtained from the corresponding bromohydrines. The reaction affords either a single product or a mixture of cis and trans isomers, according to the location of the substituents in the piperidazine ring. The stereochemistry of these compounds is studied from their ¹H NMR spectra and by X-rays diffraction methods.     

Synthesis of 1,2-benzoquinones by the oxidation of 1,4-benzodioxins by peroxide derivatives

The oxidation reaction of 1,4-benzodioxin 1 by m-chloroperbenzoic acid (m-CPBA) and t-butyl hydroperoxide (t-BHP) are reported. 1,2-Benzoquinone 2 was given in moderate yields by the m-CPBA oxidation of 1,4-benzodioxin 1 , while 1,2-benzoquinone 2 was predominantly formed by t-BHP oxidation.     

Epoxidation of bromostyrene – butadiene cotelomers

The synthesis of low-molecular-weight copolymers of bromostyrenes and butadiene and their epoxidation is discussed. The copolymers contain in the same molecule an elastomeric part, a flame-retardant part, and epoxy groups. Two epoxidation routes were studied: by an in situ generated peracid and by m-chloroperbenzoic acid. The latter is preferred, but limited to about 40% epoxidation. Epoxidation occurs mainly at the 1,4 structure of the butadiene segments. The cure of these copolymers with a tetra functional epoxy resin and diaminodiphenyl sulfone is discussed. The epoxides and their cured systems are thermally stable.     

Modification of silicon-substituted polynorbornenes by epoxidation of main chain double bonds

Postpolymerization modification of metathesis Si-containing polynorbornenes by epoxidation of double bonds of the main chain was carried out for the first time. New polynorbornenes containing one or two side Me₃Si substituents in a monomer unit and oxirane fragments in the main chain were obtained and characterized. Some features of epoxidation of polynorbornenes by 1.1-dimethyldioxirane (formed in situ) or m-chloroperbenzoic acid were studied. It was shown that m-chloroperbenzoic acid was an effective epoxidation agent, which did not affect Si?C bonds in polynorbornenes. It was found that the preparation of high-molecular-weight epoxidated polynorbornenes required one to introduce an oxidation inhibitor into the reaction mixture and to perform the reaction in toluene. Chlorine-containing solvents, such as chloroform and chlorobenzene, promoted the destruction of polynorbornenes. It was shown that the introduction of oxirane fragments into the polynorbornene main chain increased its T _g by 15?40°C.     

Cooperative effect by a hydroxy and ether oxygen in epoxidation with a peracid

Examples are given for a cooperative effect by a hydroxy group and ether oxygen in directing the steric course of epoxidation with $\text{m}$-chloroperbenzoic acid.     

The preparation of 4- and 6-chloro-2-chloromethylpyridine

6-Chloro-2-chloromethylpyridine is prepared from 6-chloro-2-methylpyridine by a route in which the 2-Me substituent was successively converted to 2-acetoxymethyl, 2-hydroxymethyl and finally to the required 2-chloromethyl substituent. Attempts to simultaneously monochlorinate the Me group and reduce the N-oxide function of 6-chloro-2-methylpyridine-N-oxide with methanesulphonyl chloride and p-toluenesulphonyl chloride gave only very small yields of 6-chloro-2-chloromethyl-pyridine. 4-Chloro-2-chloromethylpyridine is prepared from 2-methylpyridine-N-oxide by nitration, followed by substitution of the 4-nitro group by chloro using conc HCl; side chain chlorination of the 2-Me group using p-toluenesulphonyl chloride yields 4-chloro-2-chloromethylpyridine. Phosphoryl chloride reacts with 2-chloromethylpyridine-N-oxide hydrochloride to yield only 14.4% of 4-chloro-2- chloromethylpyridine, together with 2-chloromethylpyridine (2.2%), 2-dichloromethylpyridine (41.6%) and 6-chloro-2- chloromethylpyridine (41.8%). Attempts to N-oxidise 2-chloromethylpyridine with peracids led to either 2-hydroxymethylpyridine (peracetic, m-chloroperbenzoic and performic acid) or no reaction (pertrifluoroacetic acid); none of the peracids led to any detectable N-oxidation.     

Eugenol derivatives of higher chlorocyclophosphazenes and related epoxy oligomers

The synthesis of eugenol derivatives of octachlorocyclotetraphosphazene and mixtures of oligomer chlorocyclophosphazenes [NPCl₂]_3–8 was performed. Not yet described octakis(4-allyl-2-methoxyphenoxy)cyclotetraphosphazene was isolated in the crystalline form and identified via ³¹P and ¹H NMR spectroscopy, laser mass spectrometry, DSC, and TGA. Oligomers with epoxy numbers of 15–16% and molecular masses from 1400 to 1800 were prepared via epoxidation of the synthesized eugenol derivatives with m-chloroperbenzoic acid. Some assumptions on the nature of side reactions occurring in the course of epoxidation were made.     

Unexpected regioselectivity observed in the bromination and epoxidation reactions of p-benzoquinone-fused norbornadiene: An experimental and computational study

The bromination reaction of p-benzoquinone-fused norbornadiene was studied at various temperatures (?78, ?50, 0, 25, and 77 °C). At room temperature, the double bonds of the p-benzoquinone units were mainly brominated. The double bond of the norbornene unit also underwent a bromination reaction in a yield of only 2%. However, the reaction at ?78 °C resulted in the formation of products derived from the attack of bromine on the norbornene double bond with higher charge density. In contrast to the bromination reaction, the epoxidation reaction of the same compound with m-chloroperbenzoic acid and dimethyldioxirane exclusively resulted in the formation of products derived from the addition to the double bond of norbornadiene. The regioselectivity observed was investigated and the results were supported by theoretical calculations.     

Epoxidation of Multiblock Copolymers of Norbornene and Cyclooctene

The epoxidation of double bonds in random multiblock copolymers of norbornene and cyclooctene is studied for the first time. The initial copolymers with different composition and average block length are synthesized via the cross-metathesis reaction between polynorbornene and polycyclooctene in the presence of the first-generation Grubbs catalyst. New multiblock copolymers containing oxirane fragments in the backbone are obtained with a yield of 85–92% through epoxidation conducted under the action of m-chloroperbenzoic acid in toluene. The kinetics of epoxidation of polynorbornene, polycyclooctene, and their multiblock copolymers in deuterochloroform and deuterobenzene is investigated via the in situ monitoring of transformation of double bonds using ¹Н NMR spectroscopy. It is shown that on the whole the modification of cyclooctene units occurs more easily in copolymers than that in the homopolymer. The thermal properties of epoxidized homo- and copolymers are examined. It is found that upon epoxidation the glass-transition temperature and the melting temperature of multiblock copolymers increase by 40–50 and 20–30°С, respectively, wherein the degree of crystallinity and the temperature of melting grow with the length of the cyclooctene block.     

Oxidation and chlorination reactions of perfluoroketene-N,S-acetals

The paper presents the results of the investigation of oxidation and chlorination reactions of perfluoroketene-N,S-acetals. Oxidation reactions of perfluoroketene-N,S-acetals proved to be dependent on the nature of oxidizing agent and led to the formation of corresponding sulfone in the case of m-chloroperbenzoic acid or amides of α-H-perfluoroalkane carboxylic acids in the case of tert-butyl hydroperoxide or hydrogen peroxide. Reaction of 1-tert-butylsulfanyl-2,3,3,4,4,4-hexafluoro-1-[N-methyl,N-((S)-α-methylbenzyl)amino]-but-1-ene with sulfuryl chloride demonstrated the chlorination of perfluoroketene-N,S-acetals as a new approach in the synthesis of chiral α-chloro perfluoroalkane carboxylic acid amides.     

Thermal rearrangements of polybutadienes with different vinyl contents

A study was made of the loss of double bonds in equibinary (1,4-1,2) polybutadiene (EB) and in polybutadienes with 30% 1,2, 70% 1,4 (FI), and 10% 1,2, 90% 1,4 (DI) double-bond content, when heated in vacuum under nonpyrolytic conditions (temperature range 220–280°C). These polymers were found to undergo second-order loss of 1,2 unsaturation with similar activation energies (E_a = 34.0 ± 3 kcal/mole), by analogy to the previously reported thermally induced loss of double bonds in 1,2-polybutadiene (VB) (E_a = 33.6 ± 3 kcal/mole). Moreover, EB and FI exhibited also second-order loss of 1,4 unsaturation, with E_a ca. 36 and 40 kcal/mole, respectively, while DI showed negligible loss of 1,4 unsaturation below 260°C, in common with cis-1,4-polybutadiene (CB) (with 2% 1,2 double bonds) examined earlier. The loss of 1,2 double bonds in the various polybutadienes with different vinyl contents is accompanied by substantial methyl production, ranging from about one methyl group formed for every 4–5 vinyl units lost in VB, to one methyl for every two vinyls lost in EB, and to almost one methyl for each vinyl lost in DI or CB. Mechanisms are proposed for the thermally induced loss of 1,2 and 1,4 unsaturation in various polybutadienes and for the accompanying methyl production.     

Epoxy oligomers based on eugenol cyclotriphosphazene derivatives

Oligomers of hexakis(4-allyl-2-methoxyphenoxy)cyclotriphosphazene have been synthesized and their molecular structure studied by X-ray and NMR analysis. The nonplanar character of a phosphazene cycle is established, and the bond lengths P-N and valence angles N-P-N are shown to change in narrow ranges (1.5771–1.5894 Å and 117.80°–118.37°, respectively). During epoxidation of hexakis(4-allyl-2-methoxyphenoxy)cyclotriphosphazene by m-chloroperbenzoic acid or peracetic acid, in addition to hexaepoxy derivatives, the corresponding dimer is formed due to partial intermolecular interaction of epoxy groups.     

Substituent directed regioselective synthesis of 2-oxonicotonic acids and methyl nicotinates

An innovative synthesis of aryl tethered 1,2-dihydro-2-oxopyridine-3-carboxylic acids has been developed through nucleophile induced ring transformation of methyl 6-aryl-4-methylsulfanyl-2H-pyran-2-one-3-carboxylates using either cyanamide or arylamidine in excellent yields. Further, the reaction of methyl 6-aryl-4-methylsulfanyl-2H-pyran-2-one-3-carboxylates with formamidine acetate under analogous reaction conditions did not follow the same course of reaction and produced methyl nicotinate, regioselectively, in good yield. Decarboxylation of a 6-aryl-4-methylsulfanyl-1,2-dihydro-2-oxopyridine-3-carboxylic acid has been achieved by heating in PPA. The 4-methylsulfanyl substituent in 3 has also been oxidized to the corresponding methylsulfonyl group with m-chloroperbenzoic acid.     

The chemical effects of photo-oxidation on butadiene rubber

The photo-oxidation of butadiene rubber (BR) was studied in detail using films of a commercially available material, containing 33% cis-1,4-, 56% trans-1,4- and 12% 1,2-vinylic units. The spectral data of the products showed that during photo-oxidation the following functional organic groups are formed: hydroperoxides, alcohols, ketones, carboxylic acids and esters. ¹³C-NMR spectroscopic evidence for the formation of epoxides is presented. By comparison with spectra of model compounds, signals were assigned to ester and carboxylic acids in the allylic position of the oxidized polymer. The presence of ketones and carboxylic acids was also proved by chemical methods. It could be demonstrated that the formation of ketones, carboxylic acids and esters occurs from the photolysis of the OO bond of the hydroperoxides. Kinetic measurements with films containing benzophenone showed a strong increase in the quantum yield for the formation of products in comparison with the pure polymer sample. The opposite effect is observed with films containing the commercially used anti-oxidant, 2,6-di-t-butyl-p-hydroxytoluene. Also, the quantum yield for formation of the oxidation products decreases with increase in the light intensity. This result shows that cross-linking plays an important role in the photo-degradation of BR.     

Model compound studies related to peroxidases-II: The chemical reactivity of a high valent protohemin compound

The chemical reactivity of the model analog to compound I of the peroxidases resulting from the reaction of “chelated protohemin” and m-chloroperbenzoic acid is examined. The model intermediate shows no H-atom abstraction or O insertion activity and substrate reactivity depends only on the E_{$\text{1}\text{2}$} value of the substrate. A Marcus theory treatment of the available kinetic data for HRP suggests that the oxidative pathway for substrate oxidations is an outer-sphere electron transfer. From the results of the model catalyzed oxidation of 1,4-cyclohexadiene to benzene, an alternate mechanism for cytochrome P-450 catalyzed hydroxylations is suggested.     

A contribution to the volumetric electrometric determination of some organic peroxides in alkaline media

Conditions for the determination of DBP, CHP, MEKP, and MCHP, as well as m-chloroperbenzoic acid, with a standard solution of SnII-glyc or SnII-sorb by the potentiometric, bipotentiometric, and biamperometric method were found. Quite good results were obtained in comparison with individual modifications of the iodometric method. Large positive errors were found only for the determination of m-chloroperbenzoic acid with SnII-glyc. The reductometric procedure is an advantage in the determination of organic peroxides by this procedure.     

Gas-transport properties of epoxidated metathesis polynorbornenes

The effect of postpolymerization epoxidation of metathesis polynorbornenes on their gas-transport behavior is studied. For two polymers, unsubstituted polynorbornene and poly(trimethylsilylnorbornene), postpolymerization modification via double bonds is implemented by epoxidation under the action of m-chloroperbenzoic acid to high conversions (95–100%). For initial polymers and their epoxidation products, the permeability and diffusion coefficients are measured and the solubility coefficients are estimated. It is shown that, for both initial polymers, functionalization leads to a marked reduction in permeability (by a factor of 2–10) and diffusion coefficients (by a factor of 3–10); simultaneously, the separation factors increase by a factor of 2–6. Although for all gases the solubility coefficients decrease as a result of epoxidation, the coefficients of CO₂ solubility in both epoxidated polymers increase. This effect may be explained by specific interactions of a СО₂ molecule possessing the quadrupole moment with С–О–С bonds appearing in a polymer.     

Epoxidation of bacterial polyesters with unsaturated side chains. II. Rate of epoxidation and polymer properties

Poly(3-hydroxyoctanoate-co-3-hydroxy-10-undecenoate)s (PHOUs) with controlled amounts of unsaturated repeating units were epoxidized to various extents with m-chloroperbenzoic acid (MCPBA) in homogeneous solution. The epoxidation reaction was second order, with an initial rate constant of 1.1 × 10⁻³Lmol^−1.s⁻¹ at 20°C, regardless of the unsaturated unit content in PHOU. No substantial change in either molecular weight or molecular weight distribution occurred as a result of epoxidation, but the melt transition temperature and enthalpy of melting both decreased as the unsaturated groups were increasingly converted into epoxide groups. In contrast, the glass transition temperature (T_g) increased by approximately 0.25°C for each 1 mol % of epoxidation, irrespective of the composition of the PHOU. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2381–2387, 1998     

Oxidation of arylamidoximes by various chemical and biomimetic systems: comparison with their oxidations by hemeproteins

Oxidation of 4-chlorobenzamidoxime by various chemical systems leads to the corresponding amide and nitrile, and to three dimeric compounds in greatly variable amounts as a function of the oxidizing agent. Monoelectronic oxidants, such as Pb(OAc)₄ and Ag₂CO₃, selectively led to 4-chlorobenzonitrile, whereas hydroperoxides such as H₂O₂ and tBuOOH only led to 4-chlorobenzamide. Other oxidants like m-chloroperbenzoic acid and Br₂ gave more complex mixtures. Introduction of an ironporphyrin catalyst in the oxidation performed by tBuOOH and m-chloroperbenzoic acid resulted in a spectacular increase of the formation of 4-chlorobenzonitrile. These results suggest that high-valent porphyrin ironoxo species preferentially oxidize arylamidoximes in a manner similar to monoelectronic oxidants.     

CARBON-13 NMR STUDY OF MOLECULAR MOTION OF 1, 2-POLYBUTADIENES IN SOLUTION Ⅰ. STRUCTURE DEPENDENCE OF MOLECULAR MOTIOM

Proton decoupled, partially relaxed, Fourier-transform 50.3 MHz carbon-13 NMR in naturalabundance was used to determine spin-lattice times (T_1) and nuclear Overhauser enhancement fac-tors (NOE) of individual carbon of a serics of 1,2-polybutadienes with different structures in solutionin CDCl_2 The structure dependence of molecular metion and the internal motion of vinyl group in1,2-polybutadiene have been studied by nT_1 and NOE values. The nT_1 values of the carbons in cis-1,4-units are the highest and those of the carbons in 1.2-units are the lowest in three types of units in1,2-polybutadiene. The nT_1 values of carbons in the same unit become greater when the adjacent1,2-units are replaced by 1,4-units, and nT_1 values of the carbons in all units decrease sharply withthe increase of content of 1,2-units in the polymers. The fact that nT_1 values of --CH=are larger than those of=CH_2 in vinyl group impliesthat there are complex internal motions of vinyl group. It is shown by calculation that the dominantfactor causing the difference in nT_1 of--CH=and=CH_2 in vinyl group is a swing of vinyl group ina plane peopndicular to the chain backbone.