A Convenient Transformation of 2-Alkylidenecycloalkanones into Alkyl-Substituted Bicyclo[n.1.0]alkan-1-ols: Application to the Synthesis of Capsaicin
作者:Oleg Kulinkovich、Dzmitry Kananovich、Dzmitry Zubrytski
DOI:10.1055/s-0029-1219568
日期:2010.4
Treatment of 2-alkylidenecycloalkanones with hydrogen iodide in benzene and subsequent reaction of the obtained β-iodo ketones with zinc dust in THF in the presence of chlorotrimethylsilane or titanium(IV) chlorotriisopropoxide led to exo- and endo-(n+3)-alkylbicyclo[n.1.0]alkan-1-ols in high yields. Cyclization of the intermediate β-iodo ketones under these conditions proceeded in a moderate to good diastereoselectivity, and the resulted bicyclic cyclopropanols were easily separated by column chromatography over silica gel. exo-7-Isopropylbicyclo[4.1.0]heptan-1-ol obtained in this manner was efficiently employed as a key intermediate in the synthesis of capsaicin.
用氢碘酸处理2-烷基烯烃环酮,并在苯中进行反应,随后用锌粉在四氢呋喃中,在三甲基氯硅烷或四氯化钛三异丙基氧化物的存在下与所得到的β-碘酮反应,得到了高产率的外型和内型(n+3)-烷基双环[n.1.0]烷-1-醇。在这些条件下,中间体β-碘酮的环化反应表现出适度到良好的非对映选择性,所得到的双环环丙醇可以通过硅胶柱层析轻松分离。这种方法获得的外型7-异丙基双环[4.1.0]庚醇被有效地用作辣椒素合成中的关键中间体。