Treatment of silyl enol ethers and alk-1-ynes with SnCl4–Bu3N reagent followed by DBU, leads to cyclopent-2-enones, through [3 + 2] cycloaddition reactions; the initial carbon–carbon bond formation is carbometallation of alkynes, and the second step is a base-promoted intramolecular alkylation which reductively eliminates tin species (DBU = 1,8-diazabicyclo[5.4.0]undec-7-ene).
用 SnCl4-Bu3N 试剂处理
硅基烯醚和烷-1-炔,然后用
DBU 处理,可通过 [3 + 2] 环加成反应生成环戊-2-烯酮;最初的碳-碳键形成是炔的碳
金属化,第二步是碱促进的分子内烷基化,还原消除
锡物种(
DBU =
1,8-二氮杂双环[5.4.0]十一碳-7-烯)。