Science of Synthesis

Aggarwal, P.; Bebbington, M. W. P., Science of Synthesis Knowledge Updates, (2012) 2, 406.

The 6-substituted 3-amino-1,2,4-triazin-5(4H)-ones ‌39‌ (X1 = O) have been reported to undergo cyclization on reaction with glyoxal in either dioxane or ethanol to give imine-containing 7-hydroxyimidazo[1,2-b][1,2,4]triazin-3(7H)-ones ‌40‌. Subsequent addition of an alcohol nucleophile (X2 = O) from the opposite face to the bulky hydroxy moiety gives 2-substituted 6-alkoxy-7-hydroxy-6,7-dihydroimidazo[1,2-b][1,2,4]triazin-3(5H)-ones ‌41‌ (X1 = X2 = O) as the trans-adducts (‌Scheme 25‌).[‌22‌] It is important to note that these reactions are completely regio- and diastereoselective, as confirmed by 1H NMR, 13C NMR, and X-ray diffraction studies. Related reactions using thiones (X1 = S) and sulfur nucleophiles (X2 = S) have also been reported.

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