5-烷基-2-(4-氰基苯基)-1,3-二噁烷的合成

Synthesis of 5-Alkyl-2-(4-Cyanophenyl)-1,3-Dioxanes

对 5 烷基 2 (4 氰基苯基 ) 1,3 二 口恶烷的合成进行了研究 ,以 5 戊基 2 (4 氰基苯基 ) 1,3 二口恶烷的合成为例 ,论述了以溴代烷和丙二酸二乙酯为初始原料 ,采用相转移催化烃基化反应合成了 2 戊基丙二酸二乙酯 ,收率 91 7% ;进而以四氢铝锂和硼氢化钠为还原剂于 0～ 2 0℃在四氢呋喃溶剂中合成了 2 戊基丙二醇 ,收率≥ 80 % ;再与对氰基苯甲醛在催化剂氯化钙存在下反应合成了 5 戊基 2 (4 氰基苯基 ) 1,3 二 口恶烷 ,收率≥ 90 %。

For the use of liquid crystals,synthesis of 5-alkyl-2-(4-cyanophenyl)-1,3-dioxanes was studied,for instance, 5-pentyl-2-(4-cyanophenyl)-1,3-dioxane(Ⅲ) .Thus,with diethyl malonate and 1-bromopentane as starting materials,via alkylation under phase-transfer catalysis,diethyl 2-pentylmalonate (Ⅰ) was prepared in 91.7% yield.Ⅰwas then reduced with lithium aluminium hydride or sodium borohydride in tetrahydrofuran at 0-20 ℃,giving 2-pentylpropane-1,3-diol (Ⅱ) in ≥80% yield.Cyclocondensation of Ⅱwith p-cyanobenzaldehyde in the presence of calcium chloride or p-toluenesulfonic acid gave Ⅲin ≥90% yield.The structure of Ⅲwas confirmed by 1HNMR and IR.