Abstract:

According to anti?Bredt rule,if olefin strain (OS) of alkene with double bond in bridgehead is less than 71 kJ/mol,it can be isolated at room temperature.The OS of bicyclo[4.2.1]?1(8)?nonylene is less than 71 kJ/mol,conforming with anti?Bredt rule.A novel synthetic route of gram?scalable bicyclo[4.2.1]?1(8)?nonylene was reported,which was synthesized in seven steps with 17% overall yield,characterized by starting from 2?cycloheptenone using a vinyl magnesium bromide?mediated 1,4?conjugation as addition and an intramolecular Wittig reaction as the key steps.Different from the previous synthesis,the raw materials used in this method are all commercially available,which avoids the synthesis of raw materials themselves and simplifies the synthesis route.In addition,intramolecular Wittig reaction is used as the key reaction to avoid the generation of isomers.It is very challenging to synthesize alkene with double bond in bridgehead because of their high strain energy and instability.However, development of synthetic routes for such compounds is of great significance for further study of their chemical properties and application.

Key words: Bicyclo[4.2.1]?1(8)?nonylene, Vinyl magnesium bromide, 1,4?Conjugation addition, Intramolecular Wittig reaction

摘要：

根据反Bredt规则，桥头双键化合物的烯烃应变能(Olefin Strain，OS)若小于71 kJ/mol，在室温条件下则可分离。双环[4.2.1]?1(8)?壬烯化合物的烯烃应变能小于71 kJ/mol，属于反Bredt规则分子。提出了一条新的合成路线，由2?环庚烯酮出发，以乙烯基溴化镁参与的1,4?共轭加成和分子内Wittig反应为关键步骤，以七步反应和17%总收率完成了双环[4.2.1]?1(8)?壬烯的克级规模合成。不同于以往的合成，本课题组采用的原料均商业可得，避免了原料自身的合成，简化了合成路线。此外，采用分子内Wittig反应作为关键反应，避免了异构体的生成。由于桥头双键化合物具有高张力和结构不稳定性，因而合成该类化合物具有很大的挑战性。但是，发展此类化合物的合成方法对于深入研究其化学性质和应用价值具有重要意义。

关键词: 双环[4.2.1]?1(8)?壬烯, 乙烯基溴化镁, 1,4?共轭加成反应, 分子内Wittig反应