An Unusual DominoRetro-Ene–Conia Reaction: Regio- and Stereoselective One-Carbon Ring Expansion of Fenchol Derivatives
作者:Georg Rüedi、Dimitri N. Laikov、Hans-Jürgen Hansen
DOI:10.1002/hlca.200490180
日期:2004.8
Conia reaction. In contrast, a Ph substituent at C(2) in 7 allowed only the passage through a diradical species to provide phenone 26, which was converted by regioselective Baeyer–Villiger oxidation to the optically active cyclopentanol 29. Both reaction channels, the domino retro-ene–Conia rearrangement and the diradical-promoted H-transfer, have been shown to proceed highly stereoselectively. The
2-外型-取代的葑醇衍生物1 - 7,从容易地制备( - ) -在良好至优异的产率葑酮,通过动态气相热异构化(DGPTI)热解。在约200摄氏度的温度下。620℃,具有羟基烯丙基(基板1 - 4)或hydroxypropargyl部分(6)进行的初始后向下的C(2)C(3)键的裂解烯反应以形成烯醇烯中间体,没有丢失光学活动。然后这些中间体经历互变异构化为相应的α,β-不饱和酮或随后的ConiaFenchone系统的一个碳环膨胀下的重排成双环[3.2.1]辛烷骨架。在异丙烯基底物3的情况下,空间拥挤的Conia产物通过两个Me自由基的逐步损失进行了新型的'脱乙烷反应',从而产生了热力学上有利的烯酮21。在乙炔基底物6的情况下观察到类似的弛豫行为,其在Conia反应后显示出显着的1,3-Me位移,导致α,β-不饱和环状酮25。最弱的单键中的均裂1 - 3原来是竞争的反应途径。除了通过互变异构化