Abstract: The present inventors found a novel method for reducing formyl groups with the use of a Lewis acid and a hydride reducing agent in a production method for a 3-methyl-4-haloindole derivative. The present inventors also found that demethylation and/or dehalogenation of the derivative are suppressed by this method, making post-treatment easier or the derivative obtained at a high yield.

Abstract: The present invention relates to a novel method for producing diarylpyridine derivatives, and the object of the present invention is to provide a novel, industrially useful method. The present inventors developed a novel method for synthesizing pyridine rings without using palladium, a strong base, or a high-temperature reaction. In particular, they successfully developed a method that can be used to synthesize iminium salts as intermediates, synthesize cyano compounds from these iminium salts, and cyclize the cyano compounds into pyridines under very mild reaction conditions.