铜催化共轭乙烯基联烯硅和1,3-二烯硅合成

Copper-catalyzed synthesis of conjugated vinyl-substituted allenylsilanes and 1,3-dienylsilanes

在温和反应条件下,铜催化间隔烯炔衍生物与有机硅烷硼酸酯化合物发生反应,通过调控有机硅硼试剂的用量,以较高产率分别制备共轭乙烯基联烯硅和1,3-共轭二烯硅产物.该方法为制备多取代立体选择性官能团化联烯和1,3-共轭二烯产物提供了简单、高效的合成工具.

Various organosilanes are very useful building blocks in organic synthesis and material science.Among them,the allenylsilanes and 1,3-dienylsilanes are potentially reactive intermediates because they bear with multiple reaction sites.However,the studies on utilities of these compounds have been greatly restricted by the rarity of practical methods to access the allenylsilanes and 1,3-dienylsilanes as well as to expand their substrate scopes.In most cases,the strategy to access these two kinds of compounds is preinstalling a silyl group in the starting material.Apart from this,the applications of various organometallic reagents and/or noble transition-metal catalysts to synthesize these compounds are alternative pathways.Therefore,the development of general and low-cost catalytic approaches is highly desirable.In this protocol,we developed a copper catalyzed C—Si bond formation reaction between the polysubstituted-pent-1-en-4-yn-3-yl acetates and silylboronate reagent.In the presence of 5% CuCN as catalyst and 20% NaOMe as additive,the vinyl-substituted allenylsilanes as products could be formed via apropargylic substitution process in methanol solution at room temperature.Under the standard reaction conditions,different aryl-substituted pent-1-en-4-yn-3-yl acetates successfully reacted with silylboronate reagent to form the vinyl-substituted allenylsilanes products in high yields.However,these vinyl-substituted allenylsilanes were not stable enough for isolation.Therefore,the copper-catalyzed tandem reactions of silyl-substitution/protosilylation were further conducted.With increasing the loading of silylboronate reagent in reaction to 2.5 equiv,the 1,3-dienylsilanes were obtained as products.According to the effect of substituents in the polysubstituted-pent-1-en-4-yn-3-yl acetates,two sets of optimal conditions were established to improve the yields of 1,3-dienylsilane products.The controlled experiment showed that the unstable vinyl-substituted allenylsilane is the intermediate to form the 1,3-dienylsilane in the presence of copper catalyst.This work provides simple and efficient synthetic tools for preparing the multi-substituted functionalized allene and 1,3-conjugated diene products.