Nucleophilic substitution of hydrogen in 3,6-diphenyl-1,2,4-triazine 4-oxide

Reactions of 3,6-diphenyl-l,2,4-triazine 4-oxide 1 with indoles 2a,b in the presence of acid give the products of substitution of the H(5) atom, 5-(indolyl-3)-l,2,4-triazines 3a,b; the reaction of 1 with CH-acids in the presence of triethylamine also yields substitution products 5, and the derivative of ditriazinylmethane 6 was isolated along with product 5 in the reaction of 1 with acetyl- and benzoylacetone.