Catalytic generation of vinylthionium ions. (4 + 3)-Cycloadditions and Friedel-Crafts alkylations.
Catalytic generation of vinylthionium ions. (4 + 3)-Cycloadditions and Friedel-Crafts alkylations.
复制标题
催化生成乙烯基硫鎓离子。
作者：
Michael J. Topinka;R. R. Tata;M. Harmata
将3-苯基硫烷基取代的烯丙醇及其酯分别用布朗斯特酸或金催化剂处理，以产生乙烯基硫鎓离子。这些物种与二烯反应，主要是取代的呋喃，得到（4 + 3）-环加成或Friedel-Crafts烷基化的产物。结果合理化的基础上逐步机制，其中环关闭与质子损失的相对速率在中间体σ-配合物决定的过程中的反应。
A 3-phenylsulfanyl-substituted allylic alcohol and an ester thereof were treated with Brønsted acids or a gold catalyst, respectively, to generate vinylthionium ions. These species react with dienes, primarily substituted furans, to give products of either (4 + 3)-cycloaddition or Friedel-Crafts alkylation. The results are rationalized on the basis of a stepwise mechanism in which the relative rates of ring closure versus proton loss in the intermediate σ-complex determine the course of the reaction.