硼氢化钠还原9-亚芴基丙二腈的反应机理研究

Study on the Mechanism of Reduction of 9-Fluorenylidenemalononitrile with NaBH_4

主要研究了在脱氧及氧气饱和条件下,NaBH4还原9-亚芴基丙二腈(FDCN)的反应.实验结果表明:NaBH4在反应中会发生电子转移,反应首先产生α-位碳负离子.在脱氧条件下,α-位碳负离子经质子淬灭形成相应的还原产物,在CH3CN-CH3OD组成的混合溶剂中,主要的产物是9-d-FDCNH,并且延长反应时间和提高温度都会提高它的产率;在氧气饱和条件下,会有氧化产物9-芴酮(FDO)的生成.这些表明反应通过一个非完全协同的负氢转移机理来进行,即电子转移稍快于氢原子转移.

The reduction of 9-fluorenylidenemalononitrile （FDCN） by NaBH4 in oxygen-free and saturated oxygen condition was studied respectively in this paper. The results showed that electron transfer can occur and a-carbon-anion produced firstly in the reaction system. In oxygen-free condition, the proton attacked a-carbon-anion to generate the corresponding reduction product. In the CH3CN-CH3OD mixed solvent, the yield of major product 9-d-FDCNH was improved on prolonging the reaction time or increasing reaction temperature. In saturated oxygen solution, the generation of oxidation product 9-fluorenone （FDO） was due to the incoordinate hydride transfer mechanism. In other words, electron transfer was slightly faster than hydrogen atom transfer.