Banert Klaus, Chityala Madhu, Korb Marcus
Organic Chemistry, Chemnitz University of Technology, Strasse der Nationen 62, 09111, Chemnitz, Germany.
Faculty of Science, School of Molecular Sciences, The University of Western Australia, 35 Stirling Highway, Crawley, Perth, Western Australia, 6009, Australia.
Chemistry. 2020 May 15;26(28):6158-6164. doi: 10.1002/chem.202000089. Epub 2020 Apr 30.
Although the chemistry of elusive tricyanomethane (cyanoform) has been studied during a period of more than 150 years, this compound has very rarely been utilized in the synthesis or modification of heterocycles. Three-membered heterocycles, such as epoxides, thiirane, aziridines, or 2H-azirines, are now treated with tricyanomethane, which is generated in situ by heating azidomethylidene-malonodinitrile in tetrahydrofuran at 45 °C or by adding sulfuric acid to potassium tricyanomethanide. This leads to ring expansion with formation of 2-(dicyanomethylidene)oxazolidine derivatives or creation of the corresponding thiazolidine, imidazolidine, or imidazoline compounds and opens up a new access to these push-pull-substituted olefinic products. The regio- and stereochemistry of the ring-enlargement processes are discussed, and the proposed reaction mechanisms were confirmed by using N-labeled substrates. It turns out that different mechanisms are operating; however, tricyanomethanide is always acting as a nitrogen-centered nucleophile, which is quite unusual if compared to other reactions of this species.
尽管难以捉摸的三氰甲烷（氰基甲酸）的化学性质已被研究了150多年，但该化合物在杂环的合成或修饰中很少被使用。如今，环氧化合物、硫杂环丙烷、氮杂环丙烷或2H-氮杂环丙烯等三元杂环与三氰甲烷反应，三氰甲烷可通过在45℃的四氢呋喃中加热叠氮基亚甲基丙二腈原位生成，或通过向三氰甲烷钾中加入硫酸来制备。这会导致环扩展，形成2-（二氰基亚甲基）恶唑烷衍生物，或生成相应的噻唑烷、咪唑烷或咪唑啉化合物，并为这些推挽取代的烯烃产物开辟了一条新的合成途径。讨论了环扩展过程的区域化学和立体化学，并通过使用氮标记的底物证实了所提出的反应机理。结果表明，不同的机理在起作用；然而，与该物种的其他反应相比，三氰甲烷钾总是作为以氮为中心的亲核试剂，这相当不寻常。
