Tofacitinib citrate intermediate impurity and preparation method thereof

The invention provides a preparation method of a tofacitinib citrate intermediate impurity (compound I), which comprises the following steps: adding sodium hydride in batches at 0-10 DEG C, heating the material to room temperature after adding, and then slowly heating the material to 50-70 DEG C for reaction, wherein the molar ratio of the compound II to the sodium hydride is 1:0.4-1:0.6, and the reaction time is 30-40 hours. In the post-treatment process, water or isopropanol is dropwise added for quenching, and after a crude product is obtained, ethyl acetate and n-heptane are used for recrystallization. The quality of the tofacitinib citrate can be better controlled due to the discovery of the impurity. 本发明提供了一种枸橼酸托法替布中间体杂质(化合物I)的制备方法，在0～10℃下，将氢化钠分批加入，加完后升温至室温，然后缓慢升温至50～70℃反应。化合物II与氢化钠摩尔比范围为1∶0.4～1∶0.6，反应时间为30～40小时。后处理的过程中，先滴加水或者异丙醇淬灭，得到粗品后，用乙酸乙酯和正庚烷进行重结晶。这个杂质的发现可以更好地控制枸橼酸托法替布的质量。