Oxidation of α,β-Unsaturated Ketones by Organophotocatalysis Using Rhodamine 6G Under Visible Light Irradiation: Insight into Reaction Mechanism

The oxidative transformation of α,β-unsaturated ketones was investigated under the visible light-induced photocatalytic conditions using rhodamine 6G as an organophotocatalyst. In this organocatalysis, a mild co-oxidant BrCCl3 acts not only as a quencher toward the activated photocatalyst species having reductant property but also as a brominating reagent for the intermediate radicals. This study shows that the bromine atom-transfer to intermediate radicals from BrCCl3 is a key step in the reaction mechanism of our oxidation method.

The xanthine oxidase and its associated activities of the ovine milk and liver: distinctive in impact of in vivo molybdenum

Xanthine oxidase is molybdenum and iron-containing flavoprotein, catalyzing the final oxidation stage of purines and oxidative transformation of pterins and some aliphatic and aromatic aldehydes. Despite the importance of this enzyme, the distribution of xanthine oxidase in traditional household animal’s milk and tissues is unknown. Formerly, we have found most of the xanthine oxidase molecules in animal milk are inactive because of a lack of molybdenum. Ovine milk was processed by inserting in vivo molybdenum (tungsten) into drinking water. We gave opposite dates in the presence of tungsten too. Heating the milk of animals at 80 °C for 5 minutes in the presence of molybdenum and cysteine led to a sharp increase of xanthine oxidase and its associated – nitrate reductase and nitrite reductase activities. The change of xanthine oxidase and its associated activities were examined by spectrophotometry after treatment. It was established that metal ions added in drinking water for animals have an impact on enzyme activities. The activity is formed in the ovine liver even in the absence of exogenous molybdenum in drinking water. The associated activities of liver enzymes in the presence of molybdenum in drinking water had slightly increased. Tungsten-containing water led to the loss of all activities of liver xanthine oxidase. It is proposed that the liver contains a special protein involving in the incorporation of molybdenum (or tungsten) into xanthine oxidase molecule, however, the milk or mammary gland compounds lack this protein.

Oxidative Dimerization of 1Н-Benzo[f]chromenes: Synthesis of Benzannulated Analogues of Spirobiflavonoids Welwitschins E and F

A new oxidative transformation of 1H-benzo[f]chromenes into spirodimers under the action of selenium dioxide was discovered, leading to spirodimers, which are dibenzannulated analogues of naturally occurring welwitschins E and F. In the reaction, both MnO2 and I2O5 can also be used as an oxidant. The protocol has advantages of mild reaction conditions and simple operation. At the same time, oxidation of 1H-benzo[f]chromenes with (diacetoxyiodo)benzene is accompanied by the formation of 3,3′-bibenzo[f]chromene as a dimer of a different structure. It was also found that 4H-chromenes under the action of various oxidants are cleaved to give chalcone.