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DOI: 10.1055/sos-SD-026-00532

Landais, Y.; Vincent, J. M.Science of Synthesis, (200526672.

Photosensitized oxygenation of α-diazo ketones gives 1,2-diketones, for example, 3-diazoc­amphor 124 provides the 1,2-diketone 126 together with the corresponding anhydride 127. The reaction is thought to proceed through the intermediacy of a carbonyl oxide species 125 (Scheme 30).[‌98‌] meso-Tetraphenylporphyrin (TPP) is generally used as a sensitizer but methylene blue is equally efficient.[‌98‌,‌99‌] However, this method is not generally utilized and improved results are obtained by carrying out the oxygenation with oxidants such as 3-chloroperoxybenzoic acid[‌100‌] or dimethyldioxirane (e.g., conversion of 128 into trione 129);[‌101‌] generally near quantitative yields of 1,2-diketones are produced using this approach. A two-step protocol also provides good yields of 1,2-diketones through consecutive treatment of α-diazo ketones with triphenylphosphine and sodium nitrite under acidic conditions.[‌102‌,‌103‌] The sequence probably involves a phosphazine intermediate, which is then oxidized by the nitrous acid.[‌103‌]

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