Electrochemical oxidation of 1,2-diols with a catalytic amount of an organotin compound and a bromide ion as mediators has been developed. Various cyclic and acyclic 1,2-diols were oxidized into the corresponding alpha-hydroxyketones in good to excellent yields without C-C bond cleavage. Also, oxidation with the use of chemical oxidants was accomplished in the presence of a catalytic amount of an organotin compound. These reactions could discriminate 1,2-diols from isolated hydoxyl groups or 1,3-diols. In the case of a conformationally restricted cyclic 1,2-diol, the axial hydroxyl group was oxidized exclusively. Mono-, di-, and trialkylated tin compounds were examined as mediators and dialkylated tin compounds showed higher catalytic activity than mono- and trisubstituted ones. Me(2)SnCl(2) was found to be the most suitable mediator for the selective oxidation.

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The synthesis of a series of diverse methyl and benzyl γ‐ylidenetetronate derivatives was accomplished through the condensation of methyl and benzyl tetronates with (hetero)aryl aldehydes in a new two‐ or three‐step aldolisation/dehydration sequence. The bromination of methyl and benzyl γ‐ylidenetetronates occurred under mild conditions to provide the corresponding C‐3‐brominated γ‐unsaturated lactones. Di‐ and tribrominated γ‐lactones were prepared under slightly different conditions. Some brominated materials were employed in representative Stille, Suzuki–Miyaura, and Sonogashira cross‐coupling reactions to yield functionalized methyl and benzyl γ‐ylidenetetronate derivatives. Compounds that resulted from the Sonogashira cross‐coupling reactions were desilylated and converted into 1,2,3‐triazole derivatives through a copper(I)‐catalyzed 1,3‐dipolar cycloaddition reaction with benzyl azide.

A Rapid Entry to Diverse -Ylidenetetronate Derivatives Through Regioselective Bromination of Tetronic Acid Derived -Lactones and Metal-Catalyzed Postfunctionalization. -The synthesis of a series of -ylidenetetronate derivatives is accomplished through a new aldolization/dehydration sequence. Subsequent bromination succeeds regioselectively and the obtained products are suitable precursors for well known Stille, Suzuki-Miyaura, and Sonogashira cross-coupling reactions as well as for 1,3-dipolar cycloadditions (no downstream transformations shown). -(CHOPIN, N.; YANAI, H.; IIKAWA, S.; PILET, G.; BOUILLON*, J.-P.; MEDEBIELLE, M.; Eur. J. Org. Chem. 2015, 28, 6259-6269, http://dx.

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Oxidation O 0212 Efficient Oxidation of 1,2-Diols into α-Hydroxyketones Catalyzed by Organotin Compounds. -The process is accomplished using electrochemical or chemical procedures. The more hindered, secondary hydroxyl group is oxidized exclusively [→(V)] or predominantly [→(X)]. Only 1,2-diols are suitable substrates; no reactions are observed for 1,3-diols such as (XII). In restricted cyclic diols such as (XIV) or (XVI) only the axial hydroxyl group is oxidized. -(MAKI, T.; IIKAWA, S.; MOGAMI, G.; HARASAWA, H.; MATSUMURA, Y.; ONOMURA*, O.; Chem. Eur. J. 15 (2009) 21, 5364-5370; Grad. Sch. Biomed. Sci., Nagasaki Univ., Nagasaki 852, Japan; Eng.) -Kieslich 39-034

The bromination of several methyl and benzyl γ‐ylidenetetronates, which are prepared following literature procedures, is examined and a preliminary reactivity study of these bromination products in further reactions is performed.