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桃小食心虫性信息素是由Tamaki等人分离并经鉴定为顺-7-二十烯酮-11(7a)和顺-7-十九烯酮-11(7b)比例为20:1的混合物。最近,陈德恒等人提出了一条利用有机硅试剂合成顺式烯烃的方法,其立体选择性在95％以上。本文报道应用该法合成桃小食心虫性信息素的结果(见图示1)。这条合成路线具有原料比较易得,产率高和具有较好的立体选择性的优点。首先,三甲基烯丙基硅烷(1)在Schlosser’s碱(n-BuLi/t-BoOK)作用下生成的负离子与溴代缩醛2发生具有立体专一性和区域选择性的烷基化反应,产生优势量的γ-烷基化产物3和少量的α-烷基化产物。因为α-产物能够在催化量的氢碘酸存在下很容易地脱去硅基,这样我们就能除去少量的α-产物而得到纯的γ-产物3。通过具有立体选择性的碘代反应可把3转化为碘代顺式烯烃4.4在Pd(PPh_3)_4催化下与有机锌试剂偶合得到的烯烃缩醛,再在酸性的硅胶柱上水解得到醛5.5
Peach beetle sex pheromone was isolated by Tamaki et al. And identified as a 20: 1 mixture of cis-7-eicosen-11 (7a) and cis-7-nonadecen-11 (7b) Recently, Chen et al. Proposed a method of synthesizing cis-olefins using a silicone reagent with a stereoselectivity of over 95%. This paper reports the application of this method to synthesize peach moxa pheromone results (see Figure 1). This synthetic route has the advantages of relatively raw materials, high yield and good stereoselectivity. First, trimethylallyl silane (1) undergoes stereospecific and regioselective alkylation with the bromoacetal 2 on the anion formed by Schlosser’s base (n-BuLi / t-BoOK) Yielded a predominant amount of y-alkylated product 3 and a small amount of a-alkylated product. Since the α-product is able to easily remove the silicon group in the presence of a catalytic amount of hydroiodic acid, we can remove small amounts of the α-product to give pure γ-product 3. Through stereoselective iodination, 3 can be converted to iodo-cis olefins. 4.4 Alkene acetals obtained by coupling with organozinc reagents under Pd (PPh_3) _4 catalysis were hydrolyzed on acidic silica gel column to give aldehydes 5.5