Reactions of 5-phenyl-1,2,4-triazin-3-one with indoles and ortho-phenylenediamine

5-(Indol-3-yl)-5-phenyl-3-oxo-2,3,4,5-tetrahydro-l,2,4-triazines 3a,b have been obtained upon treatment of 5-phenyl-l,2,4-triazin-3(2H)-one 1 with indoles 2a,b; the starting material 1 was regenerated when 3a was treated with bromine in acetic acid, and the reaction of 1 with ortho-phenylenediamine 4 in the presence of HCl yielded 2-phenylquinoxaline 6.