Regiospecific Synthesis of 1,4-Diaryl-5-cyano-1,2,3-triazoles and Their Photoconversion to 2- or 3-Cyanoindoles

Abstract

We report the synthesis of 1,4-diaryl-5-cyano-1,2,3-triazoles from azides and alkynes via two copper-mediated steps. Aryl-substituted cyanotriazoles are emissive in nonpolar solvents. When the N¹-aryl group is electron-donating, the photoconversion of a cyanotriazole to a cyanoindole is efficient. Each of the seven pairs of 4- and 5-cyanotriazole isomers is photoconverted to either distinctive cyanoindoles without rearrangement or a major cyanoindole product via the presumed common intermediate azirine. The resulting cyanoindoles appear to be stronger emitters in polar solvents than the parent cyanotriazoles.