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25.2.1.1.2 Method 2: Oxidation via Bromomethyl Ketones

DOI: 10.1055/sos-SD-025-00278

Olpp, T.Science of Synthesis, (200725426.

Bromomethyl ketones 11 are found to be suitable precursors for glyoxals by oxidation of the derived acetates or pyridinium salts with bromine.[‌36‌‌40‌] A direct oxidation, however, can be effected by simply dissolving bromomethyl ketone 11 in the oxidant dimethyl sulfoxide (Scheme 4, Method A; Kornblum oxidation).[‌41‌] There is also an indirect pathway via easily accessible nitrate esters 12[‌38‌] that allows the formation of glyoxals 13 by nitrite elimination effected by weak bases such as triethylamine (Method B)[‌42‌] or sodium acetate (Method C).[‌43‌] The latter process where dimethyl sulfoxide is only the solvent, not an oxidant, tolerates functional groups such as azides,[‌44‌] diaziridines,[‌45‌] or pyridine derivatives[‌46‌] (for the latter compare with Section 25.2.1.1.1). The most useful variation is the combination of the bromination and oxidation step starting from methyl ketones 10, which proceeds via 11 without its isolation (Method D).[‌47‌] Bisglyoxals are prepared by Method A[‌13‌] as well as Method D[‌48‌] and the successful use of chloromethyl ketones[‌49‌] is also reported.

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