Highly regioselective heterocyclization reactions of 1H-1,2,4-triazole-3-thiols with chloroacetylenephosphonates
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- 作者：Elena B. Erkhitueva ; Albina V. Dogadina ; Andrey V. Khramchikhin ; Boris I. Ionin
- 关键词：Chloroacetylenephosphonates ; Binucleophiles ; Thiazolotriazole ; Thione-thiol tautomerism ; Heterocyclization ; Phosphorylated thiazolotriazoles ; Zwitterions ; 15N NMR spectroscopy
- 刊名：Tetrahedron Letters
- 出版年：2012
- 出版时间：15 August, 2012
- 年：2012
- 卷：53
- 期：33
- 页码：4304-4308
- 全文大小：650 K
文摘
1-Chloroacetylene-2-phosphonates react with 1H-1,2,4-triazole-3-thiols in anhydrous acetonitrile with high regioselectivity to form the fused heterocycles, 6-(dialkoxyphosphoryl)-3H-thiazolo[3,2-b][1,2,4]triazol-7-ylium chlorides 1-5. A significant difference from the previously known reactions of binucleophiles with haloacetylenes is the involvement of both acetylenic carbon atoms in the heterocycle formation. A reaction mechanism is hypothesized that assumes the formation of a sulfenium cation at the acetylene C-1 atom followed by attack of the C-2 atom by the ring N-2 atom. Compounds 1-5 easily lose one alkyl group from the dialkoxyphosphoryl fragment to form zwitterions (e.g., 6-8) which further can be transformed into inner salts 9 and 10 when heated with concentrated hydrochloric acid.