When primary aromatic amines 6 are heated under reflux with slight
excesses each of crude 1,5-dichloropentan-3-one 4 and toluene-4-sulfonic
acid monohydrate in dry methanol solution, and an excess of trimethyl
orthoformate is then added to the reactants, the corresponding
1-arylpiperidin-4-one dimethyl acetals 9 are obtained in good
(74–81%) overall yields. The dimethyl acetals 9 undergo hydrolysis in
formic acid–water (9∶1 v/v) at room temperature to give the
parent 1-arylpiperidin-4-ones 8 in virtually quantitative yields. When the
dimethyl acetals 9 are allowed to react with an excess each of
N,N-diisopropylethylamine and boron trifluoride–diethyl
ether complex in dichloromethane solution at 0 °C they are
converted in good yields into the corresponding enol ethers 10, which are
required as reagents in the solid phase synthesis of
oligoribonucleotides.
将芳香族
伯胺 6 与粗
1,5-二氯戊烷-3-酮 4 和
甲苯-4-
磺酸一
水合物在干燥的
甲醇溶液中各自略微过量后在回流下加热,然后向反应物中加入过量的
原甲酸三甲酯,即可得到相应的 1-芳基
哌啶-4-酮二甲基
乙缩醛 9,总产率为 74-81%。二甲基
乙缩醛 9 在室温下于
甲酸-
水(9∶1 v/v)中
水解,得到母体 1-芳基
哌啶-4-酮 8,产率几乎为定量。当二甲基
乙醛 9 与过量的
N,N-二异丙基乙胺和
三氟化硼二
乙基醚络合物在 0 °C 的
二氯甲烷溶液中反应时,它们会以良好的收率转化为相应的烯醇醚 10,这些烯醇醚是固相合成寡核苷酸所需的试剂。