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17.2.2.3.1.2.5 Cyclization of 3-Amino-1,2,4-triazin-5(4H)-ones with Glyoxal

DOI: 10.1055/sos-SD-117-00219

Aggarwal, P.; Bebbington, M. W. P.Science of Synthesis Knowledge Updates, (20122406.

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 1HNMR, 13CNMR, and X-ray diffraction studies. Related reactions using thiones (X1=S) and sulfur nucleophiles (X2=S) have also been reported.

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