
%0 Journal Article
%A Brown, DJ 
%A Shinozuka, K 
%T Triazolopteridines. I. Simple s-Triazolo[4,3-c]pteridines and their derived [1,5-c] isomers
%J Australian Journal of Chemistry
%D 1981/01/01
%V 34
%N 1
%P 189-194
%K 
%R https://doi.org/10.1071/CH9810189
%U https://www.publish.csiro.au/paper/CH9810189 
%X The reaction of appropriate pteridin-4-ylhydrazines (3) with orthoesters has been used to prepare s-triazolo[4,3-c]pteridine (la) and some C-methylated derivatives. Most of these underwent a Dimroth-like rearrangment to yield the isomeric s-triazolo[1,5-c]pteridines (2) but the 3-ethyl derivative(lc) gave an unusually stable intermediate, N-[3-(5´-ethyl-1´,2´,4´-triazol-3´-yl)pyrazin-2-yl]- formamide (4a), which resisted re-closure. In an attempt to prepare the parent rearranged heterocycle (2a) independently, the last intermediate, N-acetoxy-N´-(pteridin-4-yl)formamidine (6d), failed to cyclize: instead, it lost acetic acid to give pteridin-4-ylcyanamide (6e). The main systems (1) and (2)are easily distinguished by their characteristic n.m.r. spectra but not by u.v. spectra. 
