Synthesis of Cadinanolide Type of Tricyclic<i>α</i>-Methylene-<i>γ</i>-lactone Using Intramolecular Cyclization of<i>α</i>-Trimethylsilylmethyl-<i>α</i>,<i>β</i>-Unsaturated Ester with Cyclic Ketone
作者:Chiaki Kuroda、Kunihito Ito
DOI:10.1246/bcsj.69.2297
日期:1996.8
Fluoride-promoted intramolecular cyclization of ethyl 6-(2-oxocyclohex-1-yl)-2-(trimethylsilylmethyl)hex-2-enoate afforded ethyl 2-(1-hydroxybicyclo[4.4.0]decan-2-yl)acrylate as the major product, together with tricyclic α-methylene-γ-lactone, a model compound of cadinanolides. The former product was also converted to γ-lactone. The cyclization reaction promoted by TiCl4 gave the hydroxy ester and its dehydrated product. Both Lewis acid- and fluoride-promoted cyclizations gave a trans-decaline system mainly. This stereoselectivity is completely different from that of Reformatsky cyclization observed by Dreiding and co-workers.
在氟化物的促进下,6-(2-氧代环己烷-1-基)-2-(三甲基硅甲基)己-2-烯酸乙酯发生分子内环化反应,得到 2-(1-羟基双环[4.4.0]癸烷-2-基)丙烯酸乙酯作为主要产物,以及三环α-亚甲基-γ-内酯(一种卡地那内酯的模式化合物)。前一种产物也转化成了 γ-内酯。在 TiCl4 的促进下,环化反应生成了羟基酯及其脱水产物。路易斯酸和氟化物促进的环化反应主要得到反式癸碱性体系。这种立体选择性与 Dreiding 及其合作者观察到的 Reformatsky 环化反应完全不同。