Some reactions of stable ozonide derived from 4H-cyclopenta[def]phenanthrene

The ozonization of 4H-cyclopenta[def]phenanthrene gave exclusively a stable monomeric ozonide in a pure crystalline state. Reduction of the ozonide afforded the corresponding dialdehyde, diol, and lactone by treatment with triphenylphosphine, lithium aluminium hydride, and sodium sulfite, respectively. Photo-irradiation of the ozonide converted it into an acid anhydride. The corresponding aldehyde acid was obtained by pyrolysis of the ozonide.     

2,2,4,4‐Tetramethyl‐1,5‐diphenyl‐6,7,8‐trioxa‐3‐thiabicyclo[3.2.1]­octane

The structure of the title ozonide, C₂₀H₂₂O₃S, produced without the use of ozone, has been defined at 123 (1) K. In the triclinic crystal, the mol­ecule has symmetry close to C_s, and its ozonide and 1,4‐oxa­thiane rings have envelope and chair conformations, respectively. The ozonide unit has an O—O bond length of 1.4721 (12) Å and a C—O—O—C torsion angle of ?1.45 (12)°.     

Ozonolysis of 18α-Oleanane triterpenoid with an alkenenitrile moiety in the five-membered ring A

A novel synthetic protocol of ozonolytic cleavage of 18α-oleanane triterpenoid with the five-membered α,β-alkenenitrile moiety dissolved in dichloromethane to selectively synthesize a 1,3-secotriterpene derivative with 78% yield was developed. Spontaneous condensations of the synthesized 19β,28-epoxy-1,3-seco-2-nor-18α-olean-3-al-1-oic acid followed by formation of unsubstituted 1,3- and 1,4-lactones were registered in reactions with sodium borohydride as a reducing reagent or oxalyl chloride as an activating agent, respectively. α-Methoxy- and α-ethoxy-substituted 1,3-lactones were obtained when the polar protic solvents methanol or ethanol were used for the ozonolysis of the alkenenitrile. Experiments on ozonolysis were carried out in combination with reduction with dimethyl sulfide. Ozonolysis of alkenenitrile in dichloromethane without reductive treatment was found out to have resulted in stable triterpene ozonide.     

‘Reductive ozonolysis’ via a new fragmentation of carbonyl oxides

This account describes the development of methodologies for ‘reductive’ ozonolysis, the direct ozonolytic conversion of alkenes into carbonyl groups without the intermediacy of 1,2,4-trioxolanes (ozonides). Ozonolysis of alkenes in the presence of DMSO produces a mixture of aldehyde and ozonide. The combination of DMSO and Et₃N results in improved yields of carbonyls but still leaves unacceptable levels of residual ozonides; similar results are obtained using secondary or tertiary amines in the absence of DMSO. The influence of amines is believed to result from conversion to the corresponding N-oxides; ozonolysis in the presence of amine N-oxides efficiently suppresses ozonide formation, generating high yields of aldehydes. The reactions with amine oxides are hypothesized to involve an unprecedented trapping of carbonyl oxides to generate a zwitterionic adduct, which fragments to produce the desired carbonyl group, an amine, and ¹O₂.     

Dimeric Sandwich‐like Ion Pairs in the Crystal Structure of Tetrabutylammonium Ozonide Ammoniate

The novel ionic ozonide {[N(C₄H₉)₄](O₃)}₄·4.75NH₃ was synthesized by ion‐exchange reaction in liquid ammonia. The crystal structure was determined by single crystal diffraction at 100 K (monoclinic space group P2₁, a = 15.014(11) Å, b = 13.696(10) Å, c = 19.890(15) Å, β = 105.407(12)°, V = 3943(5) ų, Z = 2). The structure consists of a packing of sandwich‐like dimeric ion pairs in which two ozonide anions are interspersed between two tetrabutylammonium cations. Ammonia molecules from the solvent are localized in cavities in the structure. They are involved in hydrogen bonding with the ozonide ions. The desolvated tetrabutylammonium ozonide forms stable solutions in dichloromethane which may open up novel possibilities of tapping into the synthetic potential of the ozonide ion.     

Singlet oxygen photooxygenation of furans : Isolation and reactions of (4+2)-cycloaddition products (unsaturated sec.-ozonides)

Tetraphenylporphin-photosensitized oxygenations of furan (19), 2-methylfuran (26), 2-ethylfuran (39), furfurylalcohol (24), 2-acetylfuran (40), 2-methoxyfuran (42), 2,5-dimethylfuran (30), furfural (25) and 5-methylfurfural (41) in non-polar aprotic solvents yield the corresponding monomeric unsaturated secondary ozonides due to a (4+2)-cycloaddition of singlet oxygen to these furans. With the exception of the ozonide derived from 25, the ozonides were isolated and characterized (¹H- and ¹³C-NMR spectra, etc.). In non-polar aprotic solvents, the ozonides derived from 19, 26 and 39 undergo thermal rearrangements to the corresponding cis-diepoxides and epoxylactones. Ozonide 31, derived from 30, however, dimerizes, only above about 60° is a cis-diepoxide formed from either 31 or its dimer. Rose bengal-photosensitized oxygenations of the furans in alcohols (MeOH, EtOH, i-PrOH) also produce the corresponding ozonides as the primary products of (4+2)-cycloadditions of singlet oxygen to these furans. However, reactions of the alcohols with the ozonides are too fast to allow the ozonides to be isolated. Instead, the same products are obtained as are isolated from reactions carried out by dissolving the ozonides in the alcohols. Depending on the structure of the ozonide, three pathways are available to ozonide/alcohol (ROH) interactions:(1) addition of ROH to yield alkoxy hydroperoxides; one out of several possible isomers is formed in a completely stereoselective and regiospecific reaction; (2) elimination of a bridgehead proton by ROH as a base, as observed with the ozonide derived from 19 to give hydroxy butenolide (78) in yields between 20 and 60%, and (3) ROH-attack on a carbonyl side-chain under elimination of the corresponding alkyl ester, as observed with furfural photooxygenation which yielded hydroxy butenolide (78) in high yields (95%). Interaction of ozonide 31 with tert.-butyl alcohol (t-BuOH) yields quantitatively cis-3-oxo-1-butenylacetate (81) by a Baeyer-Villiger-type rearrangement with vinyl group migration Hydrogenbonding between the alcohol and the peroxy group of the ozonides assist the heterolysis of the C—O bonds in the ozonides; the most stabilized cation develops. Front-attack of ROH on this cation explains the stereoselectivity as well as the regiospecificity of the alkoxy hydroperoxide formation; with a bulky alcohol like t-BuOH, ROH-attack on the cation is sterically hindered thus allowing a rearrangement to occur. 1,3-Dipolar cycloaddition of p-nitrophenyl azide to ozonide 31 proceeds stereoselectively to one of the isomers 87a/87b. Finally, kinetic results of furan photooxygenation in methanol show the following order of furan-reactivity towards singlet oxygen: 30 > 42 > 26 > 19 > 41 > 25, with absolute rate constants ranging from 1.8 × 10⁸ (with 30) to 8.4 × 1O⁴ M^-1P^-1 (with 25).     

Darstellung und Strukturanalyse von Natriumozonid

Synthesis and Crystal Structure Analysis of Sodium Ozonide Solutions of sodium ozonide in ammonia have been obtained starting from cesium ozonide via cation exchange in liquid ammonia. After addition of dimethyl amine and removing the solvent mixture pure sodium ozonide precipitates as a bright red microcrystalline powder. According to X‐ray powder data, NaO₃ is isotypical with NaNO₂ (I m2m; a = 3.5070(2) Å, b = 5.7703(3) Å, c = 5.2708(3) Å; Z = 2; Rietveld profile fitting, R_Int = 3.71%). The O–O‐distances (1.353(3) Å) are the longest observed so far in ionic ozonides, the angle of 113.0(2)° is the smallest. The frequencies of the fundamental vibrations of the ozonide anion as obtained by Infrared and Raman spectroscopy are shifted to higher wave numbers as the cation diameter is decreasing. Unlike the ozonides of the heavy alkalimetals NaO₃ represents a magnetically strongly coupled system (μ_eff = 1.45 μ_B at 250 K).     

Is the decomposition of the primary ozonide a concerted or stepwise process?

An ab initio SCF-MO calculation shows that both concerted and stepwise processes are equally probable for the cleavage of the primary ozonide, leading to the Criegee intermediate. The value of the corresponding activation energy is discussed, and the results are found in agreement with the stereochemistry of the reaction. A very facile ring opening is also predicted.     

Unsymmetrical ozonolysis of carbohydrate derived norbornene systems

The ozonolysis of carbohydrate derived norbornene systems in participating solvents demonstrated that different remote controlling factors could induce the regioselective fragmentation of the primary ozonide. The exo norbornene series afforded a complete regioselective process.     

Cs2Ba(O3)4 · 2 NH3, das erste ionische Erdalkaliozonid

Cs₂Ba(O₃)₄ · 2 NH₃, the First Ionic Alkaline Earth Metal Ozonide Cs₂Ba(O₃)₄ · 2 NH₃ is the first ionic ozonide containing an alkaline earth metal cation. Its synthesis has been achieved via partial cation exchange of CsO₃ dissolved in liquid ammonia. According to a single crystal X‐ray structure determination (Pnnm; a = 6.312(2) Å, b = 12.975(3) Å, c = 8.045(2) Å; Z = 2; R₁ = 4.6%; 848 independent reflections) ozonide anions, cesium cations and ammonia molecules form a CsCl‐type arrangement, where Cs⁺ and NH₃ occupy one half of the cation sites, each. Ba²⁺ is coordinated by four ozonide groups and two ammonia molecules. Because of a short hydrogen bond to one of the terminal oxygen atoms, the respective O–O‐distance in the ozonide ion is longer than the other. The shortest intermolecular O–O‐distance ever observed in ionic ozonides has been found in this compound, which can be taken as a first clue for the radical ozonide anion to dimerize like the isoelectronic SO₂^– does.     

Ozonation of hydrocarbon diene elastomers: A mechanistic study

A study of the effects of ozonation on polybutadiene, polyisoprene, and several related hydrocarbon elastomers has shown that elastomers containing di-substituted double bonds (e.g., cis-1,4-polybutadiene) give crosslinked products as well as chain scission products in nonpolar solvents, whereas those containing tri-substituted double bonds (e.g., cis-1,4-polyisoprene) give chain scission products only. Both types of elastomer, however, give only chain scission products in polar solvents. Further investigation of the ozonation of elastomers, including the effect of ozonides of monoolefins and the solvent effect has led us to postulate that the chain scission involves the attack of a second ozone molecule on the preformed ozonide, and, the crosslinking is due to the attack of the biradical carbonyl oxide on the rubber.     

Reactions of N-substituted 2,6(3,5)-dialkyl-1,4-benzoquinone imines with arenesulfinic acids

The regioselectivity in the reactions of N-arylsulfonyl-2,6-dialkyl-1,4-benzoquinone imines with arenesulfinic acids (1,6-, 6,1-, or 6,3-addition) is determined by steric factor, while in the reactions of N-aroyl-1,4-benzoquinone imines electronic effect of substituents in the quinoid ring is crucial. The reactions of N-arylsulfonyl-3,5-dimethyl-1,4-benzoquinone imines with arenesulfinic acids follow mainly the 1,4-addition pattern. N-(N-Arylsulfonylbenzimidoyl)-1,4-benzoquinone imines are capable of reacting in a way similar to both N-arylsulfonyl and N-aroyl derivatives.     

Stereoisomerism in the representative tetracyclic dispiro ozonide derived from (methylene)dicyclohexanone with the 1,5-diketo arrangement

The conditions and reasons for the stereoselective transformation of the rac form of 2,2′-(methylene)-dicyclohexanone into the meso- or rac-diastereomer of tetracyclic dispiro ozonide (1,2,4-trioxolane) in the reaction with 30% aqueous H₂O₂ in the presence of acid have been determined. A mechanism for the stereoisomerization of ozonides was proposed, and the stereochemistry of diastereomeric ozonides was established by NMR data.     

An ESR study of various anthrasemiquinone radical anions obtained by in situ electrochemical method

Electron spin resonance spectra of seven derivatives of 9,10-anthrasemiquinone and 1,4-anthrasemiquinone are studied. These radicals have been obtained by in situ electrochemical reduction of the parent molecules.The compounds studied are: 9,10- (1), 2-chloro-1,4-dihydroxy-9,10- (2), 2,3-dichloro-1,4-dihydroxy-9,10-(3), 1,4-diacethoxy-6,7-dimethyl-9,10- (4), 1,4-dichloro- (5), 1,4-dihydroxy-9,10-anthrasemiquinone (6) and 9-chloro-10-methoxy-1,4-anthrasemiquinone (7).The hyperfine coupling constants (hfs) and the corresponding g factor are given. The assignment of these hfs is justified.     

Conformational analysis—CXIII : The isomeric cyclooctadienes

1,3-Cyclooctadiene, and 1,4- and 1,5-isomers were studied by the force field method. The former is calculated to be a mixture of two conformations, one of which has a C₂ axis, and one is irregular (C₁). There are for the 1,4-isomer two conformations, a boat-boat and a boat-chair, both of which have C_s symmetry. The 1,4-isomer is substantially all in the boat-chair conformation, while the 1,5-isomer is known to be preferentially a twist-boat (C₂) conformation. The calculations indicate the 1,3-isomer is much more stable, followed in turn by the 1,4- and the 1,5. An experimental measurement of the equilibrium between the isomers was also made, and is in semi-quantitative agreement with the calculations.     

Cyclocondensation of methyl 12-aminodehydroabietate with aldehydes and cyclopentadiene. Synthesis of tricyclic diterpenoide fused to tetrahydroquinoline

Three-component cyclocondensation of methyl 12-aminodehydroabietate with cyclopentadiene and formaldehyde or acetaldehyde under acid catalysis afforded polysubstituted naphthoquinoline derivatives with fused oxetanocyclopentane and cyclopentene fragments. Ozonation of the double bond in the N-trifluoroacetyl cyclopentene derivatives gave the corresponding ozonide.     

Reaktionsanalyse durch nichtisotherme Kalorimetrie: Lösungsreaktionen von Peroxiden,Ozoniden und Trioxiden

Homogeneous solution reactions (half-life-time for 1 M solutionsτ ₂₀° > ≈ 10^?4 sec, [ΔH] > 0.5 kcal/mole) have been investigated by non-isothermal differential calorimetry. By application of a new diagnostic procedure developed by use of an analogue computer, it can be decided whether the reactions of the substances tested are formal one-step processes, or what types of reaction-mechanisms must be considered. For the decompositions of some peroxide compounds the basic mechanism types, activation energies and action constants or entropies of the starting processes were determined. The cyclic furan ozonides have similar stabilities to that of the trioxide of di-isopropyl ether. On the other hand, triphenyl phosphite ozonide is considerably more unstable and can transfer oxygen to various acceptors below its decomposition temperature.     

Filler-polymer interactions in filled polybutadiene compounds

Bound rubber in a filled rubber compound is formed by physical adsorption and chemisorption between the rubber and filler. Polybutadiene (PB) is composed of three components of 1,2-, cis-1,4-, and trans-1,4-units. Filler-polymer interactions in PB compounds filled with carbon black or silica were studied by analyzing microstructures of the bound rubbers with pyrolysis-gas chromatography. Differences in the filler-polymer interactions of the 1,2-, cis-1,4-, and trans-1,4-units were investigated. The filler-polymer interaction of the 1,2-unit is stronger than those of the cis-1,4- and trans-1,4-units. The interaction of the 1,2-unit with silica is stronger than with carbon black. Bound rubber content is decreased by treatment with ammonia. Change of the bound rubber composition after the ammonia treatment was also studied.     

Synthetic polyisoprenes studied by Fourier transform Raman spectroscopy

Fourier transform Raman spectra are presented for the cis-1,4 and trans-1,4 isomers of polyisoprenes Vibrational intensities are used to determine quantitatively the amounts of each isomer in the microstructure. Improvements over previous work are suggested for the quantitative assessment of 1,4 microstructure. Also, changes in the Raman spectrum due to oxidative degradation show that preferential oxidative degradation for the vinyl-3,4 units occurs. The α and β forms of trans-1,4 polyisoprene were studied the ν(CC) bands resolved were identified 4 cm⁻¹ apart. A study of the copolymerization of methyl methacrylate with isoprene showed that the 1,4 form is the most favoured form produced on copolymerization. Accurate cis-1,4 and trans-1,4 microstructural information could not, however, be determined.