1. The first reaction, the reaction time is too long, there are noise generation. Drop add completed need timely control, timely processing reaction<br>2. Fourth step reaction, the whole route difficult, the yield can not be improved, is not resolved at present, and the product can not get solid<br>3. The end product melting point is low, can be dissolved with petroleum ether, the application of a small amount of solvent crystallization.
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