nitrogen. The solid was filtered and addition of petroleum ether (bp 30-60°) gave a second crop. The solid was recrystallized twice from methanol to remove tin salts, giving 3.8 g of biuret as a white solid, mp 175.
The synthesis of 3‐methyl‐2‐phenylbenzimidazole‐1‐oxide (VIII) has been accomplished. Consequently, it has been possible to establish the tautomeric structure of I as 1‐hydroxy‐2‐phenylbenzimidazole (Ia). Contrary to recent observations on the parent 1‐oxybenzimidazole (IV), I shows no tendency to exist as an N‐oxide (Ib) in aqueous solution.
metastable peaks are denoted by m*. Unless otherwise specified, reagents were obtained from regular commercial sources. MgSC>4 was the drying agent used.
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