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Hydrazone iodination is an organic reaction in which a hydrazone is converted into a vinyl iodide by reaction of iodine and a non-nucleophilic base such as DBU〔''A new reaction of hydrazones'' Barton, D. H. R. , R. E. O'Brien and S. Sternhell Journal of the Chemical Society,1962, 470 - 476 (Abstract )〕〔''Studies on the oxidation of hydrazones with iodine and with phenylselenenyl bromide in the presence of strong organic bases; an improved procedure for the synthesis of vinyl iodides and phenyl-vinyl selenides'' Barton, D. H. R.; Bashiardes, G.; Fourrey, J.-L. Tetrahedron 1988, 44, 147 ( Abstract )〕 . First published by D. H. R. Barton in 1962 the reaction is sometimes referred to as the Barton reaction (although there are many different Barton reactions) or, more descriptively, as the Barton vinyl iodine procedure. The reaction has earlier roots with the 1911 discovery by Wieland and Roseeu that the reaction of hydrazones with iodine alone (without base) results in the azine dimer (structure 2 in ''scheme 1''). In the original Barton publication〔''An improved preparation of vinyl iodides'' Derek H. R. Barton, George Bashiardes and Jean-Louis Fourrey Tetrahedron Letters Volume 24, Issue 15 , 1983, Pages 1605-1608 (Abstract )〕 the reaction was optimized by using a strong guanidine base, the inverse addition of the hydrazone to an iodine solution, and by exclusion of water. When iodine as an electrophile is replaced by aromatic selenyl bromides, the corresponding vinyl selenides are obtained:〔''A new synthesis of phenylvinylselenides'' Derek H. R. Barton, George Bashiardes and Jean-Louis Fourrey Tetrahedron Letters Volume 25, Issue 12 , 1984, Pages 1287-1290 (Abstract )〕 ==Reaction mechanism== The reaction mechanism proposed in the original Barton publication is outlined as follows: The hydrazone is oxidized by iodine into a diazo intermediate. In the next step, iodine reacts as an electrophile; displacement of nitrogen then generates an iodocarbonium ion. When the reaction site is not sterically hindered, a second iodide can recombine to form the geminal di-iodide; otherwise an elimination reaction leads to the vinyliodide. When water is present, the reaction product can revert to the ketone. This reaction is related to the Shapiro reaction. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Hydrazone iodination」の詳細全文を読む スポンサード リンク
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