Doing it Twice: Asymmetric Deprotonation/Alkylation of Weiss Diketone Derivatives as Key Steps in the Functionalization of Bicyclo[3.3.0]octanes
作者:Vanessa Lutz、Natja Park、Christian Rothe、Claudia Krüger、Angelika Baro、Sabine Laschat
DOI:10.1002/ejoc.201201409
日期:2013.2
The silyl-protected allylhydropentalenone derivative 9, derived from the Weiss diketone, was functionalized by enantioselective deprotonation in the presence of lithium bis(1-phenylethyl)amide/LiCl as the chiral base, which was generated in situ from bis(1-phenylethyl)ammonium chloride [(R,R)- or (S,S)-14] and BuLi, and trapping of the resulting enolate with alkyl halide electrophiles to give pseudo-C2
在双(1-苯乙基)酰胺锂/氯化锂作为手性碱的存在下,由双(1-苯乙基)原位生成的硅烷基保护的烯丙基氢戊烯酮衍生物 9 通过对映选择性去质子化功能化氯化铵 [(R,R)- 或 (S,S)-14] 和 BuLi,并用烷基卤化物亲电试剂捕获所得的烯醇化物,得到假 C2 或 -Cs-对称双环 [3.3.0] 辛酮 10 和11.研究了手性碱和亲电子试剂对区域选择性和双立体分化的影响。考虑到双立体控制,伪 C2 对 (1R,4R)-10/(1S,4R)-10 的匹配选择性和伪 Cs 对 (1S,6R)-11/(在 (R,R)-14 存在下观察到 1R,6R)-11。然而,(S,S)-14 的使用,产生了对 (1R,4R)-10/(1S,4R)-10 的错配选择性和对 (1S,6R)-11/(1R,6R)-11 的匹配选择性,具有互补的非对映选择性取决于亲电子试剂。此外,氢戊烯酮衍生物 10a 为大环特拉姆酸内酰胺