Oxidation with Ce

The oxazoloquinolinequinone derivative 610 was prepared from the allylphenol 605 which was transformed to the alcohol 606 and then to the aldehyde 607. Subsequent debenzylation gave 608 that was oxidized with Ce(NH4)2(N02)6 to the quinone 609 that upon cyclization with ethanolamine gave the oxazoloquinolinequinone 610 which showed... 

The rate of oxidation with Ce(IV) perchlorate depends on the method of preparation . The material from certain preparations gives a deep red complex, containing two equivalents of Ce(IV) to one molecule of H2O2, which decomposes in second order fashion-presumably by means of two concerted one-equivalent oxidations of the substrate. Other preparations give no complex and decompose peroxide much faster. The difference is thought to lie in the degree of association of the oxidant cf. the Ce(IV) oxidation of iodide ion, p. 359). 

In most cases oxidation of uncharged borabenzene complexes produces cations which can only be observed electrochemically. The iron compounds 62 and 63 may serve as an example. Oxidation is fully reversible in rigorously dried CH2C12 but irreversible in more basic solvents such as THF and acetonitrile (62). Preparative oxidation with Ce(IV) salts cleanly produces monosubstituted ferricenium cations 64 (Scheme 10) (66). In contrast to the above mentioned boranediyl extrusions, the substituent at boron is retained here in the newly formed cyclopentadienyl ring. 

A synthetic application of the sonolysis of iron carbonyls is the preparation of useful ferrilactones. The alkenyl epoxides (2, R = H, Ph, 1-hexanyl) are smoothly converted to the corresponding ferrilactone complexes (3) on reaction with Fe2(CO)9 suspended in THF and sonicated at room temperature [53]. Such complexes undergo several synthetically useful transformations (Scheme 3.7) including oxidation with Ce(IV) as a route to P-lactone natural products or P-lactam antibiotics and reaction with CO to afford 5-lactones [54]. Somewhat surprisingly this reaction is efficient even in diethyl ether, a volatile solvent which delivers low cavitation energy. 

Oxidation of [Ru edta)(OH2)] produces the Ru Ru yt-oxo ion [ Ru(edta) 2(//-0)] " which was characterized by Raman spectroscopy. " Further one-electron oxidation with Ce ... 

Exercise 31-2 The cyclobutadiene iron complex, 10, has been prepared optically active, and when oxidized with Ce(IV) in the presence of tetracyanoethene gives a mixture of cyclobutadiene cycloadducts, all of which are optically inactive. 

Later on, all the protecting groups will be removed the silyl groups with fluoride and the p-methoxybenzyl ether by oxidation with Ce(IV). In Ley s recently completed synthesis9 of azadirachtin 64 after 22 years of hard labour the key intermediate was 65. You will notice benzyl ethers, acetals and a silyl ether. This is a more modem, one might almost say minimalist, use of protection. In an ideal world no protecting groups would be necessary but in a real synthesis they will almost certainly be required as we shall see in the rest of the book. But our aim should be to keep them to a minimum. 

Gentisyl quinonc isovalerate German cockroach Blultella germanica) Fs simple acylation an oxidation with Ce(IV) IIS51... 

The cobaltacyclopentadiene complex reacts with a variety of compounds containing multiple bonds to give cyclic compounds (Scheme 11.3) [21]. In some cases, the organic products remain coordinated to Co they can be removed by oxidation with Ce or Fe. ... 

Lee and Field reported a selective fluorescence detection method for the determination of some A -nitrosamines after a postcolumn reaction. The nitrosamines eluted from the column are first hydrolyzed to produce the nitrite anion, which is then oxidized with Ce" to give the fluorescent Ce. The detection limit for this method is at the ppb level. A more sensitive fluorimetric method has been developed based upon the reaction of nitrite with 2,3-diaminonaphthalene to form the highly fluorescent product l-(H)-naphthotriazole. About 10 nmol/1 of nitrite can be detected by this procedure. 

W. A similar surface polymerization of surface-active derivatives of pyrrole by the oxidation with Ce(S04)2 has been recently reported [48]. Surface films gradually formed at the interface impede the transfer of tetramethylammonium (TMA ) ions across the DCE W interface and, to a lesser extent, the transfer of PFg ions. These two examples are the interfacial radical polymerization initiated by the direct oxidation of monomers. 

Electrochemical oxidation with Ce(IV) avoids some of the deficiencies of the Ag(II) process for example, unlike Ag, Ce does not form an insoluble salt with chloride ions. Nevertheless, like the Ag(II) process, the Ce(IV) process requires large quantities of corrosive nitric acid and gener-... 

EDS applications. In addition, new test data from the ACWA Program indicate that polynitroaromatic compounds (e.g., trinitrobenzoic acid and trinitrobenzene) precipitate during treatment of liquid wastes containing explosive residues, which may be present in EDS neutralents (Winkler, 2001). Electrochemical oxidation with Ce(IV) is also dropped from track two, owing to its relative immaturity and the possibility of corrosion and plugging of the electrochemical cells as a result of higher levels of metal ions in the EDS neutralents. 

Fluorimetry was considered in the 1950s as the natural detector for pharmaceuticals, due to its improved selectivity and sensitivity compared with UV-Vis absorption. Recent FIA applications include the determination of diazepam, nitrazepam, and oxazepam in pharmaceutical formulations using acidic hydrolysis and fluorimetric detection. Oxidation with Ce(IV) and measurement of the fluorescence from the released Ce(III), which can be considered as a classical strategy, is an appropriate technique for mixtures of amoxycillin and clavulanic acid where kinetic data are used in combination with partial least-squares multivariate calibration. 

---