Oxidation with Thallium Trinitrate

A solution of 1.78 g (0.01 mol) of dipbenylacetylene in 20 mL of glyme is added to a solution of 8.9 g (0.02 mol) of thallium trinitrate in 10 mL of water containing 5 mL of 70% perchloric acid. The mixture is gently refluxed for 3 h. After the mixture has been cooled, thallium mononitrate is filtered off, and the filtrate is diluted with 100 mL of water. The mixture is extracted with two 25-mL portions of chloroform. The chloroform extract is dried with anhydrous sodium 

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A facile synthesis of allenic esters (187) is by reaction between acid chlorides (185) and phosphoranes (186) derived from a-halo-esters. Yields are 10— 70% presumably ketens are intermediates. Cyclic /3-keto-esters can serve as precursors to cyclic allenic esters by sequential conversion to the 2-pyrazolin-5-one derivatives, using hydrazine and oxidation with thallium trinitrate (Scheme 26) overall yields are around 50%. ... 

While this approach to ring expansion yielded the desired product 252 in an overall yield of 47%, photochemical (room lights) and thermal sensitivity (room temperature) of the dibromomethyl intermediates inspired the development of an alternate approach. As shown in Scheme 21, decalenone 249 could be smoothly methylenated with Tebbe reagent to provide diene 255 in excellent yield. Clean and reproducible oxidative ring expansion could then be effected with thallium trinitrate to furnish enone 252 in 62% overall yield (unoptimized). 

Methylenecyclopropane undergoes oxidative cleavage and ring expansion with thallium trinitrate in methanol to furnish in quantitative yield a mixture of the ring cleavage product l-methoxybutan-3-one and cyclobutanone in the ratio of 4 1, as in equation (28). ... 

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). 

Whereas internal acetylenes are oxidized to a-diketones, terminal acetylenes give carboxylic acids with one less carbon on treatment with thallium trinitrate [413], potassium permanganate [843], iodosobenzene with tris(triphenylphosphine)ruthenium dichloride as a catalyst [787], or a rather rare oxidant, pentafluoroiodobenzene bis(trifluoroacetate) [797] (equation 144). 

Another way of oxidizing aryl methyl ketones without degradation is by their reaction with thallium trinitrate in methanolic solution and in the... 

Oxidative cleavage of hydrazino substituents in pyridazines and phthalazines proceeds with thallium trinitrate in methanol, under mild conditions (Equation (24)) to give the corresponding methoxy derivatives in moderate yields <95JOCl466>. 

Regeneration of carbonyl compounds from 1,3-dithian 1-oxides can be accomplished using triethyloxonium tetrafluoroborate. Nitrosonium salts, and nitronium salts, either preformed or prepared in situ, are effective reagents for the cleavage of dithioacetals. Similarly hydrolysis of thioacetals can be performed with thallium trinitrate, and selective hydrolysis can also be achieved with this reagent [equation (59)]. ... 

Yamamura and coworkers [158] developed an oxidative cyclization method to construct biphenyl ether bonds by thallium trinitrate (TTN) oxidation of the corresponding O,0 -dihalophenols followed by zinc reduction. The antibiotic piperazinomycin 266) was synthesized using this method as a key cyclization step [159]. As shown in Scheme 89, the diketopiperazine 263 was subjected to TTN oxidation in MeOH to afford an inseparable mixture containing plausible intermediate 264, which was directly reduced with zinc powder in AcOH-THF to give rise to the strained 14-membered biphenyl ether 265 in 19% yield together with two other isomers. 

Thallium trinitrate has been shown to be an efficient reagent for the dehydrogenation of chroma-nones and flavanones (Table 10, entry 5). the reaction being carried out in methanol at room temperature. The addition of perchloric acid to chromanone oxidations enhances the yields and reaction rates by promotion of enolization, but qiparently was without effect on flavanones. The ease with which chimanones and similar compound may be dehydrogenated has also permitted unusual procedures such as trimethylsilyl chloride/acetic anhydride and photolysis to be used (Table 10, entries 6 and... 

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