Ceric ammonium nitrate oxidant

Figure 1. Heat developed as a function of reactant ratio for ceric ammonium nitrate oxidation in ethanol of ethyl 10-ethoxydecanoate-10-hydroperoxide...

Cava and coworkers demonstrated that ceric ammonium nitrate oxidation of 4,6,7-trimethoxytryptamines, followed by cyclization, can efficiently generate the pyrrolo[4,3,2-de]quinoline nucleus which forms the heterocyclic core of a group of marine alkaloids which includes the makaluvamines and discorhabins. <95JOC 1800> Previous studies in this area have shown that the methoxy group can subsequently be replaced by amines to provide the natural substances. 

Oxidation of these complexes releases the apical carbon atom and its substituent in the form of an organic derivative.2 Thus ceric ammonium nitrate oxidation of an RCCo3(CO)9 complex produces the carboxylic acid, RC02H, when the reaction is carried out in aqueous acetone. Thermolysis of RCCo3(CO)9 produces acetylenes or acetylene hexacarbonyl dicobalt complexes, depending on the reaction conditions. Useful applications of these cluster complexes in organic synthesis remain to be developed. 

Oxidation of diaryl u fidesJ Ceric ammonium nitrate oxidizes diaryl sulfides in high yield to the corresponding sulfoxides without ovcroxidalion to sulfoncs. The... 

Another dicarboxylic peroxy acid, peroxyphthalic acid, is used for the Baeyer-Villiger reaction of p-diketones and a-keto esters [334]. Besides peroxy acids, ceric ammonium nitrate oxidizes 2-adamantanone to 2-oxa-homoadamantanone in aqueous acetonitrile in 73% yield at 60 °C after 3 h [422]. Tetracyclone (2,3,4,5-tetraphenyl-2,4-cyclopentadien-l-one) is oxidized by ceric ammonium nitrate in aqueous acetonitrile to tetraphenyl-2-pyrone in 77% yield [422]. 

Polyethers are readily accessible by tandem radical cyclizations. For example, bis-allylether 480a,b reacts with a trimethyl tin radical and then undergoes a sequential radical cyclization to provide 481a,b in 86 and 85% yield, respectively (equation (13)) (92JA3115). A ceric ammonium nitrate oxidation of 481 was carried out in methanol and converted the stannyl moiety into the corresponding dimethylacetal. 

Production of singlet oxygen (both Eg and Ag) by selfreaction of s-butylperoxy radicals and the peroxy radicals derived from linoleic acid has very recently been confirmed by analysis of the emission spectra observed during ceric ammonium nitrate oxidation of the. appropriate hydroperoxide ( 8). 

Benzyne intermediates are probably involved in the ring-closure of 2-(or 3-) chloro-2 -(methylthio)benzophenones to thioxanthones. Xanthones were prepared analogously. Syntheses of several pharmacologically useful thioxan-thene derivatives have been described. Ceric ammonium nitrate oxidizes thioxanthene to thioxanthone. ... 

The dimethyl ethers of hydroquiaones and 1,4-naphthalenediols can be oxidized with silver(II) oxide or ceric ammonium nitrate. Aqueous sodium hypochlorite under phase-transfer conditions has also produced efficient conversion of catechols and hydroquiaones to 1,2- and 1,4-benzoquiaones (116), eg, 4-/-butyl-l,2-ben2oquinone [1129-21-1] ia 92% yield. 

H2O2—heavy-metal oxide (31), H IO, ceric ammonium nitrate, KNO2, NaBrO, andNaC102. 

The oxidation of 1-nitronaphthalene by ceric ammonium nitrate has been reported (16). The resulting 1-iiitronaphthoquinone condenses with 1,3-butadiene followed by air oxidation under alkaline conditions to form 1-nitroanthraquinone, or l-aminoanthraquinone is formed direcdy by an intramolecular redox reaction. 

Amines can also be protected by this reagent cleavage must be carried c acidic media to avoid amine oxidation. The byproduct naphthoquinone can 1 moved by extraction with basic hydrosulfite. Ceric ammonium nitrate also s as an oxidant for deprotection, but the yields are much lower. 

Dimethoxybenzyl esters prepared from the acid chloride and the benzyl alcohol are readily cleaved oxidatively by DDQ (CH2CI2, H2O, rt, 18 h, 90-95% yield). A 4-methoxybenzyl ester was found not to be cleaved by DDQ. The authors have also explored the oxidative cleavage (ceric ammonium nitrate, CH3CN, H2O, 0°, 4 h, 65-97% yield) of a variety of 4-hydroxy- and 4-amino-substituted phenolic esters. ... 

The /7-nitrophenyl ether was used for the protection of the anomeric position of a pyranoside. It is installed using the Konigs-Knorr process and can be cleaved by hydrogenolysis (Pd/C, H2, AC2O), followed by oxidation with ceric ammonium nitrate (81-99% yield). ... 

The immediate outcome of the Hantzsch synthesis is the dihydropyridine which requires a subsequent oxidation step to generate the pyridine core. Classically, this has been accomplished with nitric acid. Alternative reagents include oxygen, sodium nitrite, ferric nitrate/cupric nitrate, bromine/sodium acetate, chromium trioxide, sulfur, potassium permanganate, chloranil, DDQ, Pd/C and DBU. More recently, ceric ammonium nitrate (CAN) has been found to be an efficient reagent to carry out this transformation. When 100 was treated with 2 equivalents of CAN in aqueous acetone, the reaction to 101 was complete in 10 minutes at room temperature and in excellent yield. 

This technique is based in the fact that when cellulose is oxidized by ceric salts such as ceric ammonium nitrate Ce(NH4)2(N03)6 free radicals capable of initiating vinyl polymerization are formed on the cellulose. However, the possibility remains that the radical formed is an oxygen radical or that the radical is formed on the C-2 or C-3 instead of the C-6 carbon atom. Another mechanism, proposed by Livshits and coworkers [13], involves the oxidation of the glycolic portion of the an-hydroglucose unit. Several workers [14,15], however, have found evidence for the formation of some homopolymer. In the ceric ion method free radicals are first generated and are then capable of initiating the grafting process [16-18]. 

Other oxidizing agents may he used to degrade cyclobutadieneiron tricarbonyl in those cases in which the reactants or products are sensitive to the acidic ceric ammonium nitrate solutions, lead tetraacetate in pyridine can be used. 

Among other oxidizing agents that have been used to accomplish the conversion of ArCHs to ArCHO are ceric ammonium nitrate, ° ceric trifluoroa-cetate, and silver(II) oxide.Oxidation of ArCHa to carboxylic acids is considered at 19-11. 

Selective oxidation of methyl pyrroles 65 possessing an a-carboxylic ester and sensitive p-substituents can be accomplished using cerium triflate in methanol <96TL315>. Moreover, the resultant a-methoxymethylpyrroles 66 may be converted to dipyrrylmethanes 67 in a "one-pot" sequence by treatment with 48% HBr. The dipyrrylmethanes, in turn, can be further oxidized to dipyrryl ketones by ceric ammonium nitrate <96JHC221>. 

Amide nitrogens can be protected by 4-methoxy or 2,4-dimethoxyphenyl groups. The protecting group can be removed by oxidation with ceric ammonium nitrate.243 2,4-Dimethoxybenzyl groups can be removed using anhydrous trifluoroacetic acid.244... 

Release and Reactivity of tf-o-QMs Although the r 2-o-QM Os complexes 11 are stable when exposed to air or dissolved in water, the quinone methide moiety can be released upon oxidation (Scheme 3.8).16 For example, reaction of the Os-based o-QM 12 with 1.5 equivalents of CAN (ceric ammonium nitrate) in the presence of an excess of 3,4-dihydropyran led to elimination of free o-QM and its immediate trapping as the Diels-Alder product tetrahydropyranochromene, 14. Notably, in the absence of the oxidizing agent, complex 12 is completely unreactive with both electron-rich (dihydropyran) and electron-deficient (A-methylmaleimide) dienes. 

The reaction of aliphatic, aromatic, heterocyclic, conjugated, and polyhydroxy aldehydes with NBS and ammonia gave the corresponding nitriles in high yields at 0°C in water (Eq. 9.18).39 Ceric ammonium nitrate (CAN)40 and iodine41 are also effective as the oxidizing reagents. 

Feldman and Skoumbourdis have utilized an oxidative hydrolysis of the thioimidate with ceric ammonium nitrate (CAN) to generate dibromophakellstatin 78 as the final step in their synthetic sequence (Equation 14) <20050L929>. 

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