Industrial preparation method of 4-bromopyridazine

The invention relates to an industrial preparation method of 4-bromopyridazine. 4-bromopyridazine is prepared by taking 3,6-dichloropyridazine as a raw material trough the following four steps of (I) chlorinating 3,6-dichloropyridazine to prepare 3,4,6-trichloropyridazine white powder, (II) preparing 3,4,6-trichloropyridazine into 3,6-dichloro-4-hydroxypyridazine, (III) preparing 3,6-dichloro-4-hydroxypyridazine into 4-hydroxypyridazine, and (IV) preparing 4-hydroxypyridazine into 4-bromopyridazine. The method provided by the invention is used for synthesizing 4-bromopyridazine with high yield and has the advantages of short steps, high yield, simple reaction process, easiness in raw material getting and relatively high industrial application value.