Substituent Effects on the Photochemistry of 1,4-Disubstituted Tetrazolethiones

1. Substituent Effects on the Photochemistry of 1,4-Disubstituted Tetrazolethiones Sundeep Rayat, Department of Chemistry, Kansas State University A series of 1,4-diaryl tetrazol-5-ones 1a - fwere synthesized by copper mediated N-arylation of 1-phenyl-1H-tetrazol-5(4H)-one with aryl boronic acids, o-R1C6H4B(OH)2 where R1 = H, OMe, Cl, CF3, Br, CCH. The 1,4-diaryl tetrazol-5-ones substituted with OMe, Cl, CF3, Br underwent thionation with Lawesson’s reagent to yield the corresponding 5-thioderivatives 2b- e. The 1-(2-bromophenyl)-4-phenyl-1H-tetrazole-5(4H)-thione(2e)so obtained was subjected to lithiation/protonation and Sonogashira coupling to produce 1,4-diphenyl-1H-tetrazole-5(4H)-thione2a and 1-(2-ethynylphenyl)-4-phenyl tetrazole-5-thione 2f, respectively. Analogous to our previous studies on 1-methyl-4-phenyl-1H-tetrazole-5(4H)-thiones, the photolysis of 1,4-diaryl tetrazol-5-thiones 2a and 2f result in the formation of carbodiimidesas the major photoproduct with the elimination of dinitrogen and sulfur. Under triplet sensitization, the presence of an ethyne moiety ortho to a tetrazolethione ring in 1-(2-ethynylphenyl)-4-phenyl-1H-tetrazole-5(4H)-thionesallows the photochemically generated carbodiimides to further engage in a Schmittel reaction with itself to form the indoloquinolines. Future studies will be focused on investigating the photochemistry of the derivatives 2b to 2e.