Osmium tetroxide 3-diketonates

Selective hydroxylation with osmium tetroxide (one equivalent in ether-pyridine at 0 ) converts (27) to a solid mixture of stereoisomeric diols (28a) which can be converted to the corresponding secondary monotoluene-sulfonate (28b) by treatment with /7-toluenesulfonyl chloride in methylene dichloride-pyridine and then by pinacol rearrangement in tetrahydrofuran-lithium perchlorate -calcium carbonate into the unconjugated cyclohepte-none (29) in 41-48 % over-all yield from (27). Mild acid-catalyzed hydrolysis of the ketal-ketone (29) removes the ketal more drastic conditions by heating at 100° in 2 hydrochloric acid for 24 hr gives the conjugated diketone (30). 

Diarylacetylenes are converted in 55-90% yields into a-diketones by refluxing for 2-7 h with thallium trinitrate in glyme solutions containing perchloric acid [413. Other oxidants capable of achieving the same oxidation are ozone [84], selenium dioxide [509], zinc dichromate [660], molybdenum peroxo complex with HMPA [534], potassium permanganate in buffered solutions [848, 856, 864,1117], zinc permanganate [898], osmium tetroxide with potassium chlorate [717], ruthenium tetroxide and sodium hypochlorite or periodate [938], dimethyl sulfoxide and iV-bromosuccin-imide [997], and iodosobenzene in the presence of a ruthenium catalyst [787] (equation 143). 

The synthesis of porphyrinoids containing nonpyrrolic heterocycles is of interest for studying the intrinsic properties of porphoryins. These porphyrin-like molecules possess varying absorption and emission properties and abilities to interact with metals or other analytes. Akhigbe and Bruckner converted meso-tetraphenylporphyrine 140 to diketone 141 using osmium tetroxide and DDQ oxidation (Scheme 5.33T Oxime formation followed by a... 

Oxidation of the products by ruthenium(VIII) oxide with the TIPS group still in place gives a mixture of carboxylic acid and an a-keto acyl silane (silyl a-diketone (eq 13), an otherwise rare class of compounds compare the oxidation of disubstituted alkynes to 1,2-diketones by Ru04 9 and the osmium tetroxide-f-butyl hydroperoxide oxidation of TMS-aUcynes. ... 

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