反应详情

U.S. Pat. No. 4,996,323 (Pews) discloses a process for preparing 3,5,6-trichloropyridin-2-ol by conducting the following three separate reactions: trichloroacetyl chloride is added to acrylonitrile in the presence of a catalytic amount of copper or a cuprous salt to produce 2,2,4-trichloro-4-cyanobutanoyl chloride; the 2,2,4-trichloro-4-cyanobutanoyl chloride is cyclized by contacting it with acidic reagents, preferably in an anhydrous state, to form 3,3,5,6-tetrachloro-3,4-dihydropyridin-2-one; and hydrogen chloride can be eliminated from this dihydropyridinone compound to yield 3,5,6-trichloropyridin-2-ol in an aromatization reaction. However, the dihydropyridinone compound can alternatively split off water to yield 2,3,5,6-tetrachloropyridine. The water produced as a by-product during formation of the 2,3,5,6-tetrachloropyridine is a major contributor to yield loss via numerous side reactions.