Rearomatization of trifluoromethyl sulfonyl dihydropyridines: Thermolysis vs photolysis

In this article, we describe the static gas‐phase pyrolysis, microwave‐induced pyrolysis, and photolysis reactions of trifluoromethyl sulfonyl dihydropyridines. The goal of this work was to find a methodology that allows obtaining of substituted pyridines—which are known to be difficult to synthesize—to be reused in a new substitution reaction. We demonstrated that it is possible to achieve the rearomatization process by the elimination of the trifluoromethyl sulfonyl moiety through the 3 processes, with the static pyrolysis being the best method to obtain the substituted pyridines. In addition, we propose the 1,4‐elimination (CF 3 SO 2  + H) as the first step, since it is the less energetic process, as has also been corroborated by calculations. A competitive reaction (CO 2 extrusion) also occurs, yielding undesired products.