Alcohols cerium ammonium nitrate

Goumont et al. exploited this kind of reactivity for the nucleophilic substitution of the hydrogen atom in position 5 by carbon nuclophiles <20030BC2192> (Scheme 18). These authors reported that 6,8-dinitrotetrazolo[l,5- ]pyr-idine 11 easily reacts with potassium nitropropenide to yield an adduct similar to those obtained with alcohols 12. This adduct when oxidized by cerium ammonium nitrate yields the nitroalkyl-substituted aromatic compound 64. 

Yamashiro et al. 1972), boron trifluoride etherate in acetic acid (Schnabel et al. 1971), trimethylsylil triflate (Schmidt et al. 1987), trimethylsilyl perchlorate (Vorbrueggen Krolikiewicz 1975), and, most frequently, trifluoroacetic acid (Farowicki Kocienski 1995 and references therein). Deprotection of the /-HOC group under neutral conditions was not described until recently, yet it is highly desirable. Now it has been found that the tert-butoxycarbonyl protecting group for amines, alcohols, or thiols is removed efficiently (90-99% yield) with use of 0.2 equivalent of cerium ammonium nitrate in acetonitrile at 80°C (Hwu et al. 1996) ... 

JOC6261> and peptide isosteres <1995JOC8074>. The A, A -diprotected phenylalaninal 465 (Scheme 119) was obtained from L-phenylalanine 464 in good yield. The reaction of 465 with 2-TST provided the expected a -amino alcohol 466 as a major product. The oxidative removal of the -methoxybenzyl group with cerium ammonium nitrate (CAN, (NH4)2Ce(N03)6) and silylation furnished the compound 467, which was transformed into the aldehyde 468 in excellent yield. 

Selective oxidation of methyl groups can be achieved by platinum salts in aqueous solution. Thus, p-toluenesulfonic acid is oxidized to the alcohol and then to the aldehyde by the Pt(II)/Pt(IV) system. Likewise the methyl group of ethanol can be oxidized without affecting the hydroxyl group [208]. Potassium or sodium bromate in the presence of cerium ammonium nitrate in a water/di-oxane (2 3) mixture can oxidize toluene into a 1 1 mixture of benzaldehyde and benzoic acid. Ethylbenzenes yielded acetophenones [209]. 

Xu, X., Jiang, R., Zhou, X., liu, Y., Ji, S., and Zhang, Y. (2009). Cerium ammonium nitrate an efficient catalyst for carbon-carbon bond formation from ferrocenyl alcohol substrate. Tetrahedron, 65, 877-882. 

More recently, Menendez et al. reported a closely related four-component access to tetrahydropyridines, the amino alcohol being replaced by a primary amine and an alcohol. Thus, the cerium(IV) ammonium nitrate (CAN)-catalyzed reaction between primary aliphatic amines, 1,3-dicarbonyls, cx,p-unsaturated aldehydes, and alcohols resulted in the formation of 6-aUcoxy-2-methyl-l,4,5,6-tetrahydropyridines with... 

Apart from sodium hypochlorite, a number of alternative secondary oxidants for TEMPO-mediated alcohol oxidations can be employed. These include cerium (IV) ammonium nitrate (CAN),24 trichloroisocyanuric acid (TCCA),25 oxone ,26 MCPBA,2,3,7 PhI(OAc)2,27 W-chlorosuccinimide,28 sodium bromite,29 electrooxidation,8,21 H5IO626 and a polymer-attached diacetoxybromide (I) complex.30... 

Cerium (TV) ammonium nitrate (CAN)37 and a cerium (TV) impregnated resin38 are able to catalyze the selective oxidation of secondary alcohols with sodium bromate (NaBrOi). Stoichiometric cerium bromate— CelBrCb h, prepared in situ from barium bromate and cerium (III) sulfate, is also able to perform selective oxidations of secondary alcohols.39... 

Nitration of naphthalene by use of cerium(IV) ammonium nitrate suspended on silica gel, or in homogeneous solution, in the presence of alcohols, sodium or tetrabutylammonium nitrite and acid gives mainly l-alkoxy-4-nitronaphthalenes together with some of the 2-nitro isomers.34 The results are consistent with initial attack by N02- alone or complexed with cerium(IV) ion at the 1- and 2-positions in a ratio of 5 1. 

At the exotic end of the Lewis acid scale is tetrafluorosilane (mp -90 5C, bp -86 UC) first proposed by Corey and Yi as a mild and selective reagent for the cleavage of silyl-protected alcohols with the reactivity order being EtiSi > f-Bu-Me2Si f-BuPhiSi/ 1 The substrate in dichloromethane or acetonitrile, is stirred at room temperature under an atmosphere of excess tetrafluorosilane provided by a gas-filled balloon. The reaction is slow in dichloromethane but quite fast (ca. 15 min) in acetonitrile. In the final step of Yamamoto s synthesis of the Hemibrevetoxin B [Scheme 4.40]61 the secondary TIPS and TBS ethers were removed from 40.1 with tetrafluorosilane. Identical conditions were used by Nicolaou et al to remove two TBS ethers in the final step of their synthesis of Hemibrevetoxin B.62 In the example shown in Scheme 4,41, deprotection with fluoride (basic) or cerium(lV) ammonium nitrate (CAN) in methanol (neutral) isomerised the angelate to the more thermodynamically stable tiglate.63 However, with tetrafluorosilane, no isomerisation occurred during the deprotection step. 

Cerium(IV) ammonium nitrate in aqueous acetonitrile is an alternative oxidant for the cleavage of p-methoxybenzyl ethers.335 Compared with DDQ, it is seldom used336 337 but there are circumstances where it will work when DDQ fails. A case in point is shown in Scheme 4.182.338 The ditosylate 182.1 underwent oxidative hydrolysis in the usual way with DDQ to give the alcohol 18U in 80% yield but attempts to deprotect the monotosylate 182.3 failed under the same conditions. However, with CAN, the monotosylate gave the desired diol 182.4 in 30% yield together with the p-methoxybenzoate 1825 in 24% yield. 

Cerium(IV) ammonium nitrate in aqueous acetonitrile will also cleave a p-methoxyp/zeny/ ether (presumably to benzoquinone).335 The reaction was used in a synthesis of Stigmastellin A [Scheme 4.183] to release a primary alcohol in the presence of a benzyl ether.339 In an extension of the method, a bidirectional strategy for the synthesis of 2,3 5-trisubstitute d tetrahydrofuran components of annonaceous acetogenins benefited from the simultaneous protection of two primary hydroxyls as their Cj-symmetric hydroquinone ether [Scheme 4.184].340... 

Cyclic ethers are oxidized to lactones in the presence of cerium(IV) salts. Treatment of tetrahydiofu-ran with cerium(rV) ammonium nitrate in the presence of primary, secondary or tertiary alcdiols leads to the formation of the corresponding tetrahydrofuranyl ethers in quantitative yield. Fuitfaermoie, 4-meth-oxybenzyl ether derivatives of carbohytbates are selectively deprotected to the parent alcohols on reaction with cerium(IV) ammonium nitrate in aqueous acetonitrile. ... 

Primary benzylic alcohols (equation 10) can be oxidized in the presence of saturated primary alcohtris using a catalyst derived from ammonium cerium(IV) nitrate supported on charcoal with air as the cooxidant (under these conditions a-hydroxy ketones are oxidized to a-diketones). ... 

Ammonium cerium(IV) nitrate or cerium(IV) sulfate will catalyze the selective oxidation of secondaiy alcohols with sodium bromate as cooxidant, in this case remote C—C double bonds interfere, but 1,2-diols are not cleaved. It has been found that sodium bromite in aqueous acetic acid will act as a selective oxidant for secondary mary diols without the need for other catalysts (Scheme 21). ... 

Cerium(IV) Nitrate Test (Ammonium Hexanitratocerium(IV) Test). Dissolve 15 mg of the unknown in a few drops of water or dioxane in a reaction tube. Add to this solution 0.25 mL of the reagent and mix thoroughly. Alcohols cause the reagent to change from yellow to red. 

Alcohols were determined using ammonium cerium (IV) nitrate reagent, which reacts with alcohols to form a stable colour complex. Colour intensity was... 

The action of n-butyllithium in THF at low temperature leads to the anion. After reaction with an electrophilic compound, e hydrolysis can generally be carried out in polar solvents (acetone, alcohols, acetonitrile) in the presence of mercury(II) chloride or oxide and water.In other cases, NBS, - chloramine T, cerium(IV) ammonium nitrate, n-tributyltin hydride, trialkyloxonium tetrafluorobor-ate, thallium nitrate or photochemistry can be used. Desulfurization by Raney nickel gives hydro-carbons. ... 

Benzaldehydes can be prepared in good yield from benzyl alcohols by means of various oxidants, including dinitrogen tetroxide (for its preparation see Park and Partington412) in chloroform or carbon tetrachloride,413 concentrated nitric acid,414a aqueous hypochlorite,414b or cerium(iv) ammonium nitrate in 50% acetic acid.415... 

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