Chemie freier cyclischer vicinaler Tricarbonyl‐Verbindungen (‘1,2,3‐Trione') Teil 2. Redox‐Reaktionen von 1,2,3‐Trionen mit En‐1,2‐diolen (‘Reduktonen'), 2‐Alkoxy‐en‐1‐olen,En‐1,2‐diaminen und verwandten Spezies

Chemistry of Free Cyclic Vicinal Tricarbonyl Compounds (‘1,2,3‐Triones'). Part 2. Redox Reactions of 1,2,3‐Triones with Ene‐1,2‐diols (‘Reductones'), 2‐Alkoxy‐en‐1‐ols, Ene‐1,2‐diamines, and Related Species . Midstanding carbonyl groups of cyclic 1,2,3‐triones 4 possess outstanding electrophilic (electron‐pair accepting) as well as oxidizing (one‐electron accepting) properties. Their reactions with selected electron‐rich CC bonds as efficient nucleophiles (A_N reactions) and as efficient reducing agents (SET (single electron transfer) reactions) are studied. In a few cases, short‐lived charge‐transfer colors could be observed. Particularly, free didehydro‐5,6‐O‐isopropyliden‐L ‐ascorbic acid ( 4g ), its O,C‐adduct 8g to 5,6‐O‐isopropylidene‐L ‐ascorbic acid ( 1g ), and – via an independent pathway – the ostensible C,C‐dimer 10a of mono‐dehydrodimedone reductone were prepared. Intermediate radical anions 4 ^.− can be considered to be ideal representatives of dicapto‐dative radicals. Novel large‐scale syntheses of 3,4‐dihydroxyfuran‐2(5H)‐one ( 1e ) and of its vicinal trione 4e are presented.