氰基硼氢化钠还原喹啉合成1,2-二氢喹啉

Synthesis of 1,2-Dihydroquinolines by Reduction of Quinolines with Sodium Cyanoborohydride

1,2-二氢喹啉是一类重要的化合物.通过对已有方法的改进,发展了一类从喹啉出发高效合成1,2-二氢喹啉的反应(产率50%~96%).通过对一系列还原剂的筛选发现,当使用氰基硼氢化钠作为还原剂时,能有效克服已有方法中低转化率的问题,实现被活化的喹啉盐经还原去芳构化反应得到一系列N-烷氧羰基取代的1,2-二氢喹啉.需要指出的是,除3-位或4-位含有取代基的底物能得到单一的目标产物外,其他底物都会生成过度还原的四氢喹啉副产物,二氢喹啉与四氢喹啉比例均大于4:1.同时,该方法相较于文献中的方法操作简便,无须使用大大过量的氯甲酸酯,增强了反应的实用性.

An efficient conversion of quinolines to 1,2-dihydroquinolines(50%~96%yield)was developed via the modification of the known methods.It was found that using sodium cyanoborohydride as a reductant would overcome the low conversion often encountered in previous studies.A series of N-alkoxycarbonyl-1,2-dihydroquinolines were obtained through reduction of activated quinolium salts.Notably,with the exception of the 3-and 4-substituted substrates,a mixture of 1,2-dihydro-quinolines and the over reduced tetrahydroquinolines was obtained with the ratio over 4:1.Besides,compared to the established methods,an easy operation without using large excess of chloroformate further enhances practicability of the methodology.