6‐ and 7‐aryl‐1,2,4‐triazolo[4,3‐b]‐1,2,4‐triazines. Synthesis and characterization

Synthetic methods for the preparation of 6‐aryl‐1,2,4‐triazolo[4,3‐b]‐1,2,4‐triazines (1) and the 7‐aryl isomers (2) are described. Compounds 1 were prepared from aryl glyoxaldoximes 76 via 6‐aryl‐1,2,4‐triazin‐3(2H)ones (75). A simple procedure for the preparation of the 7‐aryl isomers was effected using arylglyoxals 11 and the triazoles (4, 12a and 12b). However, complete regioselectivity was not realized in all cases, especially when the triazoles were substituted at the C‐5 position. A regiospecific synthesis of the 7‐aryl isomers 2 was developed via the 3‐methylthio‐5‐aryl‐1,2,4‐triazines (61). The structure of the parent 6‐phenyl derivative 5 was confirmed by x‐ray crystallography.