![Sample our Food Science & Technology journals, sign in here to start your access, latest two full volumes FREE to you for 14 days]({"type":"image" , "src" : "/sda/5936/TOC-Subject-Sample-2021-Food-Science-Technology.jpg"})
Abstract
The superoxide-mediated base catalyzed autoxidation of α-oxo enols is initiated by the dcprotonation of the labile hydoxyl group. Thus, the reaction of O−2 (generated from KO 2/ crown ether in aprotic media) with 3-hydroxycoumarin (I). followed by a CH,I-workup, generates products 24 via a deprotonation-oxidation sequence complicated by a competing saponification of the lactone linkage. The related coumarin reductone (α-oxo enediol) 8 is rapidly oxidized by O−2, HO− and t-butoxide to the corresponding triketone, which in turn undergoes further oxidation and rearrangenlent ultimately yielding (upon methyl iodide workup) products 9–14. Whcn the O−2 mediated oxidation is carried out under argon in completely degassed solutions, large amounts (≥ 20%) of monodeprotonation product (detected as 9) accumulate. These results are discussed in light of the differing mechanisms proposed by Sawyer and Afanas'ev for the interaction of O−2 with the reductone ascorbic acid.