Cerium acetate ammonium nitrate

Partial oxidation of 158 by bromine yields bromine-free 159 together with mono-, di-, and tribromo derivatives. Other useful reagents are nitrous acid (54JCS286) or the one-electron oxidants silver acetate (in substoichio-metric quantity) and cerium(IV) ammonium nitrate (only for the methyl ether of 158 86BCJ511). 

Another transient aminoxyl radical has been generated , and employed in H-abstraction reactivity determinations" . Precursor 1-hydroxybenzotriazole (HBT, Table 2) has been oxidized by cyclic voltammetry (CV) to the corresponding >N—O species, dubbed BTNO (Scheme 9). A redox potential comparable to that of the HPI —PINO oxidation, i.e. E° 1.08 V/NHE, has been obtained in 0.01 M sodium acetate buffered solution at pH 4.7, containing 4% MeCN". Oxidation of HBT by either Pb(OAc)4 in AcOH, or cerium(IV) ammonium nitrate (CAN E° 1.35 V/NHE) in MeCN, has been monitored by spectrophotometry , providing a broad UV-Vis absorption band with A-max at 474 nm and e = 1840 M cm. As in the case of PINO from HPI, the absorption spectrum of aminoxyl radical BTNO is not stable, but decays faster (half-life of 110 s at [HBT] = 0.5 mM) than that of PINO . An EPR spectrum consistent with the structure of BTNO was obtained from equimolar amounts of CAN and HBT in MeCN solution . Finally, laser flash photolysis (LFP) of an Ar-saturated MeCN solution of dicumyl peroxide and HBT at 355 nm gave rise to a species whose absorption spectrum, recorded 1.4 ms after the laser pulse, had the same absorption maximum (ca 474 nm) of the spectrum recorded by conventional spectrophotometry (Scheme 9)59- 54... 

Ates, A., Gautier, A., Leroy B., Plancher, J.-M., Quesnel, Y, Vanherck, J.-C. and Marko, I.E. (2003) Mild and chemo-selective catalytic deprotection of ketals and acetals using cerium(IV) ammonium nitrate. Tetrahedron, 59 (45),... 

Diethylamino)sulfur trifluoride, 110 Formylation (see also Carbonylation) Vilsmeier reagent, 341 Fragmentation reactions Cerium(IV) ammonium nitrate, 67 Copper(II) acetate-Iron(II) sulfate, 85 Lead tetraacetate, 155 Friedel-Crafts alkylation Aluminum chloride, 15... 

Cerium(IV) ammonium nitrate (CAN) in acetic acid oxidizes potassium bromide and, consequently, brominates methylbenzenes at a benzylic position with 50-80% yield293. f-Butyl hydroperoxide (TBHP) oxidizes CuBr2 which a-brominates toluenes to benzyl... 

Benzyltrimethylsilanes, on the other hand, give products of C-Si cleavage, i.e. benzyl nitrate and acetate, on treatment with cerium(IV) ammonium nitrate in AcOH based on ring substituent effects, a one-electron transfer mechanisms seems to be in operation. 

Dimerizations of aryldiazomethanes to 1,2-diarylethylenes were reported to be catalyzed by cerium(IV) ammonium nitrate (4J), lithium bromide (42), copper(II) salts (43), and rhodium(II) acetate (44) and to be induced by photolysis (45). Catalysis of copper ion-exchanged zeolite (CuNaY) was compared with reactions of copper salts supported on AI2O3 and a homogeneous catalyst, Cu(C104)2, for the dimerization [Eq. (11)] of aryldiazomethane (Table XIII) (-/6). 

Considerable interest has been shown recently in the use of cerium (IV) salts as oxidizing agents. Cerium (IV) ammonium nitrate can also be a nitrating agent 1125]. It can also act in the presence of acetic acid 1119]. In the presence of nitric acid [120] it can form nitrate esters from the methyl group, viz. ... 

CAN serves as a convenient reagent for the generation of radicals from CH-acidic substrates (Sec. 2.4.1) [3]. Because of the comparable oxidation potential of CAN (-1-1.61 V vs NHE) and manganese(III) acetate (+1.54 V vs NHE), both one-electron oxidants exhibit a similar reactivity pattern. However, the advantage of cerium(IV) ammonium nitrate consists in the milder reaction conditions, which allow the generation of radicals in methanol or acetonitrile at lower temperatures. 

In summary, oxidative radical reactions by other metals are less common than single-electron transfer to cerium(IV), iron(III), copper(II), and especially manganese(III) complexes. However, even for manganese(III) acetate and cerium(IV) ammonium nitrate the synthetic potential is not completely utilized. During the next few years, many new applications should arise, which will focus on stereoselective reactions and the synthesis of complex organic molecules. 

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... 

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. ... 

Cerium(lll) ammonium nitrate (CAN) in acetic anhydride is also an efficient nitrating reagent for aromatic compounds [135]. The nitration of thiophene by CAN gave a mixture of 2-nitro- (58%) and 3-nitrothiophene (12%) (Scheme 86) [134]. 

---