Carbonyl compounds oxidations, cerium ammonium nitrate

TRAHANOVSKY Ether oxidation Oxidation ot aromatic ethers to carbonyl compounds with cerium ammonium nitrate... 

Acetyl- and 3-benzoylisoxazoles have been conveniently obtained by one-pot reactions of alkynes with ammonium cerium(IV) nitrate or ammonium cerium(III) nitrate tetrahydrate in acetone or acetophenone these processes probably involve 1,3-DC of nitrile oxides formed by nitration of the carbonyl compound by cerium salts <02TL7035>. 

Acetyl- and 3-benzoylisoxazoles 389 (and isoxazolines) have been prepared by one-pot reactions of alkynes (and alkenes) with ammonium cerium(iv) nitrate (CAN(lv)) or ammonium cerium(lll) nitrate tetrahydrate (CAN(m))-formic acid, in acetone or acetophenone. These processes probably involve 1,3-dipolar cycloaddition of nitrile oxides produced via nitration of the carbonyl compound by cerium salts. The existence of nitrile oxides as reaction intermediates was proved by the formation of the dimer furoxan 390 when the above reaction was carried out in absence of any dipolarophile (Scheme 95) <2004T1671>. An analogous improved procedure has been applied to alkynyl glycosides as dipolarophiles for the preparation of carbohydrate isoxazoles <2006SL1739>. 

Different from the hydroxyalkylation reactions using carbonyl compounds as substrates, Nicolaou s and Macmillan s groups developed independently the intramolecular asymmetric Friedel-Crafts-type a-arylation of aldehydes with electron-enriched arenes based on the SOMO activation strategy. Using chiral imidazolidione as catalyst, a series of cyclic aldehydes were obtained in good yields and enantioselectivities with cerium ammonium nitrate (CAN) as single electron transfer oxidant [46]. 

N03)j, a newcomer to the arena of oxidants, is useful for the acetoxylation of aromatic side chains in benzylic positions [415, 416] and for the oxidation of methylene or methyl groups that are adjacent to aromatic rings to carbonyl groups [238, 415, 417]. The reagent also oxidizes alcohols to aldehydes [418, 419, 420, 421] and phenols to quinones [422, 423], cleaves vicinal diols to ketones and a-hydroxy ketones to acids [424, 425], and converts diaryl sulfides into sulfoxides [426]. A specialty of ammonium cerium nitrate is the oxidative recovery of carbonyl compounds from their oximes and semicarbazones [422, 427] and of carboxylic acids from their hydrazides [428] under mild conditions. 

Oxidation with ammonium cerium nitrate has to be done in 100% acetic acid (equation 165). In 50% acetic acid, carbonyl compounds are... 

Oxidation and Bromination of Other Functional Groups. Selective oxidation of alcohols may be achieved using a 1 1 complex of NBS and tetrabutylammonium iodide, whereas 1,2-diols are converted into 1,2-diketones using iV-bromosuccini-mide. An efficient and mild procedure has been reported for the preparation of benzoic acids via oxidation of aromatic carbonyl compounds by employing NBS and mercuric acetate. Selective and efficient oxidation of sulfides to sulfoxides has been achieved with NBS in the presence of /3-cyclodextrin in water. Epoxides and aziridines are conveniently oxidized to the corresponding a-hydroxy or Q -amino ketones using cerium(IV) ammonium nitrate and NBS. ... 

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