Ring contraction of 1,2,4-triazin-3-ones to imidazolin-2-ones and 1,2,3-triazoles
Abstract
On treatment with hydroxylamine-O-sulphonic acid 1,2,4-triazin-3-ones undergo ring contraction to give imidazolin-2-ones in high yield. N-Aminotriazinones are proposed as intermediates but were not isolated. However, cinnolin-3-one undergoes an analogous ring contraction to oxindole and the intermediate N-aminocinnolinone was isolated and shown to rearrange to oxindole.
On treatment with ethereal chloramine at room temperature the 1,2,4-triazin-3-ones undergo a different ring contraction, via N-chloro-derivatives, to give 1,2,3-triazoles in high yield.
Mechanisms are proposed for these reactions.