(The) synthesis of α-oximinoketones using t-butyl thionitrate

Abstract

A new method to synthesize -oximinoketones using alkyl thionitrates under the mild conditions was found. The reactions of ketones with t-butyl thionitrate or t-butyl thionitrite in anhydrous tetrahydrofuran containing gaseous hydrogen chloride at 0$^\circ$C afforded the corresponding oximes. In the case of using more stable t-butyl thionitrate, the better yields of oximes were obtained than using t-butyl thionitrite probably due to the instability of t-butyl thionitrite. Since the sulfur-nitrogen bond of thionitrite and thionitrate is relatively weaker than the oxygen-nitrogen bond of nitrites and also $RS^-$ is better leaving group than $RO^-$ in the nitrosation step, thionitrates are considered to be better reagent than thionitrate or alkyl nitrite for the nitrosation of ketones. Undoubtly, this reaction appears to be initiated by nitrosation on the $\alpha$-carbon of carbonyl group. Alkyl or benzyl alkyl ketones reacted with t-buthyl thionitrate to give the corresponding $\alpha$-oximinoketones in excellent yields (80-97\%). While, in the case of bibenzoyl methan, the yield of $\alpha$-oximinoketone was low (50\%).