The Olefin Synthesis from<i>β</i>-Hydroxyalkylphosphonates Induced by Fluorides or Relatively Weak Bases
作者:Takayuki Kawashima、Takafumi Ishii、Naoki Inamoto、Norihiro Tokitoh、Renji Okazaki
DOI:10.1246/bcsj.71.209
日期:1998.1
β-Hydroxyalkylphosphonates, which were prepared readily from alkylphosphonates and carbonyl compounds, were treated with a fluoride ion such as CsF or with relatively weak bases such as K2CO3 in N,N-dimethylformamide to give the corresponding olefins in good yields. One molar equivalent of water to bases is effective for increasing the yields of olefins. The stereochemistry of erythro-dimethyl (2-hydroxy-1-methyl-2-phenyl)ethylphosphonate was determined by X-ray crystallographic analysis. Use of threo-isomer gave (E)-olefin exclusively, while that of erythro-enriched isomer afforded predominantly (Z)-olefin, indicating that the present olefination proceeds stereospecifically in a manner of syn-elimination.
利用烷基膦酸酯和羰基化合物可以方便地合成的β-羟基烷基膦酸酯,用氟离子(如CsF)或者在N,N-二甲基甲酰胺溶剂中使用相对较弱的碱(如K2CO3)处理后,可以以良好收率得到相应的烯烃产物。相较于碱而言,1当量的水的加入对于提高烯烃的产率具有明显作用。通过X射线晶体学分析,确定了赤型-二甲基(2-羟基-1-甲基-2-苯基)乙基膦酸酯的立体化学结构。使用苏型异构体时,仅得到(E)-烯烃;而使用赤型富集异构体时,则主要得到(Z)-烯烃。这表明目前的烯化反应是通过顺式消除方式进行立体专一性进行的。