Study on the Synthesis of Optically Active Silacyclopentanes and their Application to Asymmetric Synthesis

以(E，E)-二苯基-1，3-丁二烯、二烷氧基二氯硅烷和镁为原料，在三氢呋喃中一锅法合成了2，5-二苯基硅环戊烯的烷氧基衍生物，得到的硅环戊烯中含有丰富的反式异构体。与烷基三氯硅烷反应，只生成顺式异构体。这些硅环戊烯的氢化反应生成相应的硅环戊烷。然后，硅环戊烯的烷氧基衍生物与烷基溴化物反应得到2-烷基取代的1，1-二烷氧基-2，5-二苯基硅环-3-烯和未反应的硅环戊烯的反式异构体。然后，1，1-二乙氧基-2，5-二苯基硅环-3-烯与光学活性醇(1-薄荷醇和1-冰片)反应生成非对映异构体。以2，5-二溴己烷为原料，经格氏试剂与甲基二氯硅烷反应制得1，2，5-三甲基硅环戊烷，再由1-methyl-1-chloro-2，5-diphenylsilacyclopentene与环己酮反应制得硅烯醇醚。

Alkoxy derivatives of 2,5-diphenylsilacyclopent-3-ene were prepared by one-pot reaction of (E,E) -diphenyl-1,3-butadiene, dialkoxydichlorosilanes, and magnesium in THF.The obtained silacyclopentenes included trans rich isomer. The reaction with alkyltrichlorosilanes gave only cis isomer. The hydrogenation of these silacyclopentenes gave corresponding silacyclopentanes. Then the alkoxy derivatives of silacyclopentenes were lithiated with LDA.The reaction of the lithio silacyclopentenes with alkyl bromides gave 2-alkyl substituted 1,1-dialkoxy-2,5-diphenylsilacyclopent-3-enes and unreacted trans isomer of silacyclopemtenes.Next, the reaction of 1,1-diethoxy-2,5-diphenylsilacyclopent-3-ene with optically active alcohols (1-menthol and 1-borneol) were investigated and the racemic mixture gave diastereomer. Furthermore, 1,2,5-trimethylsilacyclopentane was prepared by the reaction of grignard reagent of 2,5-dibromohexane with methyldichlorosilane and silyl enol ether was prepared by the reaction of 1-methyl-1-chloro-2,5-diphenylsilacyclopentene with cyclohexanone.