N-Tosyltrifluoroacetaldehyde imine (4) reacted with terminal olefins by only heating together to give the ene reactin products. This means the imine is much more reactive than trifluoroacetaldehyde (2) itself as an enophile. However, 4 was very sensitive to moisture and the yields were low even if it was used without isolation. Further, it did not react with non-terminal olefins. In the course on study of the mechanism of this reaction, we found that N-(2, 2, 2-trifluoro-1-ethoxyethyl)tosylamide (12), obtained by the reaction of trifluoroacetaldehyde ethyl hemiacetal (1) with tosylamide (3) in the presence of titanium(IV) chloride followed by addition of ethanol, reacted in the presence of sodium hydride and titanium(IV) chloride to give the same products from the ene reaction of 4 in much better yields. Interestingly, this reaction proceeded with non-terminal olefins.
N-Tosyltrifluoroacetaldehyde
亚胺(4)仅通过加热即可与末端烯烃反应,生成烯反应产物。这意味着作为亲电试剂,该
亚胺比三
氟乙醛(2)本身更具反应活性。然而,4对湿气非常敏感,即使不经分离使用,产率也很低。此外,它不与非末端烯烃反应。在研究该反应机理的过程中,我们发现,通过三
氟乙醛乙基
半缩醛(1)与
甲苯磺酰胺(3)在
四氯化钛存在下反应,随后加入
乙醇得到的N-(2,2,2-三
氟-
1-乙氧基乙基)
甲苯磺酰胺(12),在氢化
钠和
四氯化钛存在下反应,以更高产率得到与4进行烯反应相同的产物。有趣的是,此反应还能与非末端烯烃进行反应。