Thermolysis and photolysis of arylchlorodiazirines in allyl bromide

p-Chlorophenylchlorocarbene reacts with allyl bromide to form the expected cyclopropanes. In the case of p-nitrophenylchlorocarbene, a small amount of insertion product is also formed in addition to the cycloadducts. The formation of the insertion product is attributed to the attack of the carbene on the bromine atom followed by intramolecular allylic rearrangement.     

Ultraviolet derivative absorption spectra of nylon 6,6: Effect of photolysis versus photo-induced oxidation

The irradiation of nylon 6,6 film with light of wavelengths greater than 250 nm and 300 nm has been studied using uv derivative absorption spectroscopy. Initially, the polymer showed a strong absorption at 290 nm which is associated with an α,β-unsaturated carbonyl species. Changes in the absorption band were found to be dependent on the atmosphere and are discussed in terms of a reversible photolysis versus a photo-induced oxidation process.     

Thermolysis and photolysis of some 5-amino-4-methoxycarbonyl-Δ2-1,2,3-triazolines

Thermolysis of 5-amino-4-methyl-4-methoxycarbonyl-Δ²-l,2,3-triazolines leads to amidines and 1-methoxycarbonyl diazoethane. If the N₁ substituent is a tosyl or benzoyl group, the corresponding triazoline is not isolated, the azide addition to the olefin gives directly the thermolysis products at room temperature. Triazoline photolysis leads to amino aziridines which are azomethine ylids.     

Chemistry of diazocarbonyl compounds: XXVII. Thermolysis and photolysis of diazirines, derivatives of 1,3-dioxane-4,6-dione

Photolysis of diazirines, 1,3-dioxane-4,6-dione derivatives, occurs in the presence of methanol or dimethyl sulfide as carbene traps without a formation of carbene intermediates. It was established for the first time that the thermolysis and photolysis of diazirines from the 1,3-dioxane-4,6-dione series led mainly to Wolff rearrangement with a subsequent formation of 5-oxo-1,3-dioxolane-4-carboxylic acids or their derivatives. The data obtained show that the α-oxodiazirines are the key intermediates in the photolysis and Wolff rearrangement of α-diazocarbonyl compounds.     

Formation of a methide derivative upon photolysis of thymidine bromohydrins

Reaction of bromine with thymidine in aqueous solution produces, in high yield, the corresponding 5-bromo-6-hydroxy-5,6-dihydroderivative (thymidine bromohydrins). UVC photolysis of thymidine bromohydrins gives rise to a reactive intermediate that is converted into 5-(hydroxymethyl)-2'-deoxyuridine upon incubation in water. When the former compound is left in methanol, ethanol, or propanol, the corresponding 5-alkoxymethyl derivatives are produced. The proposed structure for the primary photolysis product of thymidine bromohydrins is a methide derivative of the thymine ring. This compound could be an interesting intermediate in the synthesis of methyl-substituted thymidine.     

Characterization of an oxaluric acid derivative as a guanine oxidation product

The oxidation of guanine in the dinucleoside monophosphate d(GpT) by an oxo-metalloporphyrin generates a linear oxaluric acid derivative after heating at 65 degrees C for 30 min and at neutral pH.     

Low-temperature photosensitized oxidation of a guanosine derivative and formation of an imidazole ring-opened product

An organic-soluble guanosine derivative, 2',3',5'-O-(tert-butyldimethylsilyl)guanosine (1), was prepared and its photosensitized oxidation was carried out in several solvents at various temperatures. Singlet oxygen is the reactive oxidizing agent responsible for this reaction. Neither an endoperoxide nor a dioxetane intermediate was detected by low-temperature NMR even at -78 degrees C. A product (A) with an oxidized imidazole ring was the only major product detected at room temperature; this compound could be isolated by low-temperature column chromatography and was characterized by (1)H and (13)C and mass spectroscopy. CO(2) was the other major product. A small amount of the corresponding 8-oxo-7,8-dihydroguanosine derivative B was detected during the initial stage of the photooxidation and was shown to be intermediate in the formation of two products of extensive degradation, C and D. Reaction of 1 with the singlet oxygen analogues 4-methyl-1,2,4-triazoline-3,5-dione (MTAD) and 4-phenyl-1,2,4-triazoline-3,5-dione (PTAD) gave products consistent with a proposed mechanism involving the rearrangement of an initially formed endoperoxide to give A and B from reaction of 1 with singlet oxygen.     

Thermolysis of complex cyanides,XV

The thermal decompositions of K₂[Fe(CN)₄ L]·4 H₂O, H₂[Fe(CN)₄ L] and H[Fe(CN)L](L=1,1-bipyridine, of 1,10-phenanthroline) were studied. The experimental results showed that the protonated ferrous complexes decompose with formation of HCN at lower temperature than the corresponding potassium salts. The decomposition of K₂[Fe(CN)₄ L] starts by removal of the ligand L. HCN elimination is followed by a redox reaction with formation of cyanogen in the case of H[Fe^III(CN)₄ L].

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Zusammenfassung Die thermische Zersetzung von K₂ [Fe(CN)₄ Z]·4H₂O, H₂[Fe(CN)₄ L] und H[Fe(CN)₄ L] (L=1,1'-Dipyridin, 1,10-Phenantrolin) wurde untersucht. Die Versuchsergebnisse zeigten, dass die protonierten Ferrokomplexe unter Bildung von HCN bei niedrigeren Temperaturen zersetzt werden, als die entsprechenden Kaliumsalze. Die Zersetzung von K₂ [Fe(CN)₄ L] beginnt durch die Abspaltung des LigandenL. Nach Eliminierung des HCN folgt eine Redox-Reaktion unter Bildung von Dizyan im Falle von H[Fe^III(CN)₄ Z].

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K₂[Fe(CN)₄ L]·4₂, H₂[Fe(CN)₄ L] H[Fe(CN)₄ L] L=1,1- 1.10-. , , . K₂[Fe(CN)₄ L] L. H[Fe¹¹¹(CN)₄ L] HCN - .

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XIV. A. Hantshmann, J. Salvetter, H. Hennig and B. Mohai, Thermochim. Acta. 25 (1978) 341

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The authors thank I. Ötvös for mass-spectroscopic investigations, and Mrs. Csukás, Mrs. Csiszár and Mrs. Haeffner for experimental assistance.     

Photosensitized oxidation of methionine derivatives. Laser flash photolysis studies

The early events in the triplet 4-carboxybenzophenone (CB)-induced oxidation of N-acetyl-methionine methyl ester (N-Ac-Met-OCH₃) are investigated in aqueous solution. Upon electron transfer from the methionine residue of N-Ac-Met-OCH₃ to ³CB*, the resulting sulfur radical cation undergoes further reactions: (1) back electron transfer, (2) escape of the radical ions from the solvent cage, or (3) proton transfer and escape of the radicals. The yields and paths of these reactions are shown to depend strongly on the pH of the solution, and, similar to the previously reported results for dipeptides (Met-Gly and Gly-Met), on the structural nature of the methionine substituents. In the experiments performed in this work, low quencher concentrations were used to avoid formation of intermolecular transients (e.g., dimeric sulfur-centered radical cation (S∴S)⁺). Under these experimental conditions, the one-electron oxidized sulfur does not seem to become stabilized in an (S∴N)⁺ three-electron bonded intramolecular complex. The proposed mechanism is further supported by the stable products analysis. A detailed mechanism involving characterization of the transients is discussed and compared to that of methionine and methionine-containing dipeptides (Met-Gly and Gly-Met). Moreover, a newly installed transient absorption laser system is described in details.     

A binuclear manganese complex of a pyridoxal derivative and its use as an oxidation catalyst

Summary A new binuclear complex of manganese, [Mn₂L(OAc)₂], where H₃L = N,N-[4(3-hydroxy-5-hydroxymethyl-2-methyl)pyridylmethylene]-1,3-diamionopropane-2-ol, was prepared and characterized by analysis and various spectral methods. The studies reveal that it is a mixed valence manganese(II)/manganese(III) complex with endogenous -oxo and exogenous -carboxylato bridges.The complex can be used as a catalyst for the selective oxidation of hydrocarbons (cyclohexene, cis-cyclooctene, styrene, norbornene and trans-4-octene) using terminal oxidant at ambient temperatures. The yields calculated on the basis of the oxidant concentrations indicate that the complex works as an efficient catalyst for the oxidation of hydrocarbons. A probable mechanism for the reaction is proposed.