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Photosensitized oxidation of furans. Part 13. Trapping reactions of the carbonyl oxides obtained from some 2-methoxy-5-phenylfurans
No full textThe dye-sensitized photo-oxygenation in methanol of the 2-methoxy-5-phenylfurans (1a-c), unsubstituted at C-4 with electron-withdrawing groups, leads to the hemiperacetals (4a-c). The reaction provides the first incontrovertible evidence for carbonyl oxide intermediacy in sensitized photo-oxygenation of heterocyclic systems. Further supporting evidence is also reported. In polar non-participating solvents carbonyl oxides (5a-c) partly rearrange to the epoxides (7a-c)
Photosensitized oxidation of furans. Part 14. Nature of intermediates in thermal rearrangement of some endo-peroxides of 2-alkoxyfurans: New rearrangement pathway of furan endo-peroxides
No full text2-Methoxy-5-phenylfurans (1a-c) substituted at C-4 with electron-withdrawing groups, by dye-sensitized photo-oxygenation in non-participating solvents, give the endo-peroxides (3a-c) which by thermal rearrangement partly yield the 3H-1,2-dioxoles (14a-c). The latter, which are the first examples of this ring system, are thermally very unstable. Their formation can be deduced only from the products obtained by thermal rearrangement which are structurally related with the thermal rearrangement products of 3H-1,2,4-dioxazoles (10). The behaviour of the furans (1a-c) contrasts with that of the 2-methoxy-5-phenylfurans unsubstituted at C-4 which under the same conditions give carbonyl oxides
Carbonyl Oxide Chemistry. Part 2. Substituent and Solvent Effects on the Chemical Behaviour of Carbonyl Oxides
No full textPhotosensitized oxidation of furans. III. Comparison between photochemically and thermally generated singlet oxygen oxidation of 3‐methoxycarbonyl‐2‐methyl‐5‐phenylfuran
No full textThermal conversion of furan endo‐peroxide I, obtained by photosensitized oxidation of furan II, yields very similar results to those of the oxidation of the furan II by thermally generated singlet oxygen, showing that also in the latter case the endo‐peroxide I is the key intermediate. A mechanistic interpretation of the furan II‐singlet oxygen reaction is reported. Copyright © 1981 Journal of Heterocyclic Chemistr
Photosensitized Oxidation of Furans; Part 17: A Simple Method for the Synthesis of 5-Hydroperoxyfuran-2(5H)-ones
No full textPhotosensitized Oxidation of Furans; Part 17: A Simple Method for the Synthesis of 5-Hydroperoxyfuran-2(5H)-ones
No full textPeroxidic intermediates in the photosensitized oxidation of 2-methyl-4,5-diphenylimidazole
No full textPhotosensitized oxygenation of 2-methyl-4,5-diphenylimidazole (1) at -15°C gives 2-hydroperoxy-2-methyl-4,5-diphenyl-2H-imidazole (2) which isomerizes into 4-hydroperoxy-2-methyl-4,5-diphenyl-4H-imidazole (4), probably via the endo-peroxide (7); compound (2) and its deoxygenation product (3) are the first 2-hydroperoxy- and 2-hydroxy-2H-imidazole to be reported
Intermediates in the reaction of singlet oxygen with trisubstituted oxazoles
No full textTrisubstituted oxazoles I react at −15° with singlet oxygen to give dioxazoles III and iminoanhydrides V which rearrange at room temperature to triamides VI. The intermediate ratio (III/V) is sensitive to the reaction temperature. It is likely that at room temperature triamides VI are essentially formed via imino‐anhydrides V. Copyright © 1978 Journal of Heterocyclic Chemistr
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