Unexpected production of 2,4,6-triphenyl-1,3,5-triazine in the electroreduction of 3,4-diphenyl-1,2,5-thiadiazole 1-oxide. Theoretical estimation of reactive sites for 1-oxide and 1,1-dioxide 1,2,5-thiadiazoles

3,4-Diphenyl-1,2,5-thiadiazole 1-oxide (1a) in acetonitrile solution is electroreduced to 2,4,6-triphenyl-1,3,5-triazine and 3,4-diphenyl-1,2,5-thiadiazole. This behavior is very different from that of similar compounds with other oxidation states of the heterocyclic sulfur atom, such as the 1,1-dioxide derivative (2) and the aromatic 3,4-diphenyl thiadiazole parent ring. The Fukui functions were calculated for 1a and 2 to estimate their reactivity, compare their reactive site, and rationalize the divergent electrochemical properties of 1a.