Cc. Tzeng et al., CONDENSED 1,2,4-TRIAZINES - SYNTHESIS OF 5-BENZYL-5H-IMIDAZO[4,5-E]-1,2,4-TRIAZINE 1-OXIDES (9-BENZYL-6-AZAPURINE 6-OXIDES), Journal of the Chemical Society. Perkin transactions. I, (16), 1994, pp. 2253-2256
A number of 5-benzyl-5H-imidazo[4,5-e]-1,2,4-triazine 1-oxides, bioiso
steric isomers of antiviral 9-benzylpurines, have been prepared. Oxida
tion of mino-5-benzylamino-3-methylsulfanyl-1,2,4-triazine 1 with exce
ss of m-chloroperbenzoic acid afforded mino-5-benzylamino-3-methylsulf
onyl-1,2,4-triazine 1-oxide 2 in 75% yield. The 3-methylsulfonyl group
, which is a good leaving group, has been replaced with various nucleo
philes to give 3-amino 4, 3-methoxy 5 and 3-hydrazino 8 derivatives. O
xidative dehydrazination of 8 with mercury(II) oxide (HgO) in ethanol
gave 6-amino-5-benzylamino-1,2,4-triazine 1-oxide 9 in a moderate yiel
d. The 1,2,4-triazine 1-oxides were then cyclized with triethyl orthof
ormate (TEOF) to afford the title compounds in 28-88% yields.