Photooxygenation of Non-Aromatic Heterocycles

Photooxygenation of non-aromatic heterocycles and cyclic compounds containing non-usual heteroatoms, namely silicon, germanium and tellurium has been reviewed. All three types of photooxygenation (Types I-III) can take place. Moreover the heteroatom can be frequently involved endorsing electron-transfer reactions which turn out to be the main pathways, even in singlet oxygen oxygenation. A vast collection of novel and unexpected products are often formed, sometimes in a stereocontrolled manner

A mild photochemical approach to the degradation of phenols from olive oil mill wastewater

Photooxidation of cathecol (1) is carried out in aqueous solution at k > 300 nm using different sensitizers: rose bengal (RB), 9,10-dicyanoanthracene (DCA), 2,4,6-triphenylpyrylium tetrafluoroborate (Pyryl). The highest degradation is observed in the UV/RB-sensitized reaction (66% after 15 h of irradiation), mineralization and formation of dimers are the final events. This procedure has been extended to tyrosol (2), caffeic acid (3), vanillic acid (4), 4-hydroxycinnamic acid (5) and 4-hydroxybenzoic acid (6) as well as to a mixture of all phenols. A reduced toxicity of the UV/RB-irradiated solutions of cathecol and tyrosol towards alga Ankistrodesmus braunii is also verified

Comparative Studies on Different Citrus Cultivars: A Revaluation of Waste Mandarin Components

Peel, pulp and seed extracts of three mandarin varieties, namely Phlegraean mandarin (Citrus reticulata), Kumquat (Citrus japonica), and Clementine (Citrus clementina) were compared and characterised in terms of photosynthetic pigment content, total polyphenols amount, antioxidant activity and vitamin C to assess the amount of functional compounds for each cultivar. The highest polyphenols content was found in the Phlegraean mandarin, especially in peel and seeds, whereas Kumquat exhibited the highest polyphenols amount in the pulp. The antioxidant activity was higher in the peel of Phlegraean mandarin and clementine compared to Kumquat, which showed the highest value in the pulp. The antioxidant activity peaked in the seeds of Phlegraean mandarin. The vitamin C in the Phlegraean mandarin was the highest in all parts of the fruit, especially in the seeds. Total chlorophyll content was comparable in the peel of different cultivars, in the pulp the highest amount was found in clementine, whereas kumquat seeds showed the greatest values. As regards total carotenoids, peel and pulp of clementine exhibited higher values than the other two cultivars, whereas the kumquat seeds were the richest in carotenoids. Among the analysed cultivars Phlegraean mandarin may be considered the most promising as a source of polyphenols and antioxidants, compared to the clementine and Kumquat, especially for the functional molecules found in the seeds. Moreover, regardless of cultivars this study also highlights important properties in the parts of the fruit generally considered wastes

Photo-oxygenation of the [4+2] and [2+2] type

Series "Molecular and Supramolecular Photochemistry" (edited by V. Ramamurthy and K. S. Schanze

N‐acyl‐N‐formylcarbamates. A new class of carbamate derivatives

N‐Acyl‐N‐formylcarbamates III can be prepared in good yields by singlet oxygen oxidation of 5‐unsubstituted 4‐alkoxyoxazoles I. They are photo‐ and thermo‐stable and sensitive to hydrolysis under very mild conditions. In contrast 4‐unsubstituted 5‐alkoxyoxazole V reacts with singlet oxygen to give oxamate VII via dioxazole VI. Copyright © 1979 Journal of Heterocyclic Chemistr

Intermediates in the reaction of singlet oxygen with trisubstituted oxazoles

Trisubstituted 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

Peroxidic intermediates in the photosensitized oxidation of 2-methyl-4,5-diphenylimidazole

Photosensitized 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