Preparation method of ramelteon impurity

The invention relates to a preparation method of a ramelteon impurity, and belongs to the technical field of chemical synthesis. The preparation method comprises the following steps: (1) reacting a compound I with oxalyl chloride to generate an acyl chloride compound, adding aluminum trichloride, and carrying out a Friedel-Crafts reaction to generate a compound II; and (2) directionally generatinga compound III from the compound II under the action of Raney cobalt and hydrazine hydrate. The preparation method provides a novel and safe reduction condition for direct synthesis of the monosubstituted impurity, and the product does can be directly used as an impurity reference substance without purification, and also can be directly subjected to a subsequent impurity transfer experiment. 本发明涉及一种雷美替胺杂质的制备方法，属于化学合成的技术领域。本发明的技术方案为：(1)化合物Ⅰ与草酰氯反应生成酰氯化合物，再加入三氯化铝进行傅克反应生成化合物Ⅱ；(2)化合物Ⅱ在雷尼钴、水合肼的作用下定向生成了化合物Ⅲ。本发明的有益效果为：提供了一种新型、安全的还原条件，可以定向的合成出了一种单取代的杂质，并且无需对产物进行纯化，可知直接作为杂质对照品使用，也可以直接进行后续的杂质传递实验。