Abstract
A combination of oxalic acid dihydrate and sodium nitrite in the presence of wet SiO2 was used as an effective nitrosating agent for the nitrosation of β-diketones to their corresponding α-oximinoketones in moderate to excellent yields under mild and heterogenous conditions.
Highlights
The α-oximinoketones are known to be important intermediates for the synthesis of aminoacids [1], nitrosopyrazoles [2], 2-vinylimidazoles [3] and so on
Nitrous acid or one of its esters [4], alkyl thionitrite or thionitrate [5], nitrosyl halides [6] and sodium nitrite in acetic acid [7] are all used for the synthesis of α-oximinoketones, the yields, selectivity for mono oximination and chemoselectivity on the methylene carbon where there are two possible sites of nitrosation are low [5]
It was observed that exclusive nitrosation of acetylacetone occurred, whereas the 2,5-hexadione remained intact in the reaction mixture, even after 5 hours (Scheme 2)
Summary
The α-oximinoketones are known to be important intermediates for the synthesis of aminoacids [1], nitrosopyrazoles [2], 2-vinylimidazoles [3] and so on. Nitrous acid or one of its esters [4], alkyl thionitrite or thionitrate [5], nitrosyl halides [6] and sodium nitrite in acetic acid [7] are all used for the synthesis of α-oximinoketones, the yields, selectivity for mono oximination and chemoselectivity on the methylene carbon where there are two possible sites of nitrosation are low [5]. We wish to report a one-pot heterogeneous procedure for Molecules 2001, 6 chemoselective mono oximination of β-diketones by oxalic acid dihydrate (C2H2O4·2H2O, Pka~2) and sodium nitrite.
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