New impurity of erlotinib, and preparation method thereof

The present invention discloses a new impurity related with erlotinib synthesis, and a preparation method thereof, wherein the new impurity is 3-(3-ethynyl-phenyl)-6,7-bis(2-methoxyethoxy)quinazolin-4(3H)-imine. According to the present invention, the precise control on the N'-[2-cyano-4,5-bis(2-methoxyethoxy)phenyl]-N,N-dimethyl-formamidine and m-aminophenylacetylene synthesis reaction condition is used to prepare the new impurity, and then column chromatography separation and re-crystallization refining are performed to obtain the high purity product of the new purity; the impurity has the novel structure so as to easily perform the quality control of the erlotinib bulk drug; and the production method has characteristics of short synthesis route and simple operation, and the obtained product has the high purity and can be used for reference substance research and the like.