Perborate, oxidation with

Impurities in CL have also been destroyed by oxidation with ozone22 followed by distillation. Ozonation treatment of waste CL leaves no ionic impurities. However, the most commonly used oxidizing agents are potassium permanganate, perboric acid, perborate, and potassium bromate. Treatment of CL with these oxidizing agents is carried out in a neutral medium at 40-60°C. Strongly alkaline or acidic conditions accelerate the oxidation of CL to form isocyanates. Hie undesirable oxidation reaction is fast above pH 7 because of the reaction with isocyanate to form carbamic acid salts, which shifts the equilibrium to form additional isocyanate. 

This is an alternative method of introducing copper into an o-hydroxyazo dye structure. The azo compound is treated with a copper(II) salt and an oxidant in an aqueous medium at 40-70 °C and pH 4.5-7.0. Sodium peroxide, sodium perborate, hydrogen peroxide or other salts of peroxy acids may be used as oxidants, the function of which is to introduce a second hydroxy group in the o -position [25]. This process is reminiscent of earlier work on Cl Acid Red 14 (5.51 X = H), an o-hydroxyazo dye that will not react with a chromium (III) salt to form a 1 1 complex but will do so by oxidation with an acidified dichromate solution. This oxidation product was later found to be identical with that obtained by conventional reaction of Cl Mordant Black 3 (5.51 X = OH) with a chromium(III) salt [7]. 

Sodium perborate oxidation of alcohols by is aided by Aliquat, but also requires the addition of chromium oxide [17]. However, the long reaction times at 60-80°C and the variable yields do not make the procedure particularly attractive. In contrast, direct epoxidation of a,p-unsaturatcd ketones has been conducted with moderate success using sodium perborate catalysed by tetra-n-hexylammonium hydrogen sulphate [18, 19]. 

Bis(pinacolato)diboron 355 has also been used as a source of the analogous pyrimidine-5-boronate 357 with subsequent oxidation with sodium perborate giving 5-hydroxypyrimidines 358 in 33-96% overall yield <2006TL7363>. 

The enzyme-catalyzed stereoselective oxidations of 1,2-dithiane and l,4-dihydro-2,3-benzodithiin were also investigated <2002CC1452>. Using naphthalene dioxygenase and chloroperoxidase, enantiomerically enriched sulfoxides (1,2-dithiane 1-oxides) were obtained l,4-dihydro-2,3-benzodithiin yielded a product of 32—47% ee with an excess of the (6)-configuration while 1,2-dithiane yielded almost enantiopure (96% ee) (R)-configured 1-oxide. Finally, 1,4-dihydro-2,3-benzodithiin 2-oxide was also prepared by perborate oxidation <1988JOC2608>. 

The formation of peracids as the effective oxidizing species has often been proposed for oxidations with sodium percarbonate in the presence of organic acids or acid anhydrides30-32. It was observed that at room temperature and in dichloromethane as solvent, the addition of acetic anhydride induced the epoxidation by sodium perborate of mono-, di- and trisubstituted alkenes, including a,/i-unsaturated ketones in a slightly exothermic reaction33 (equation 6). 

Molybdenum(VI)-catalysed perborate oxidation of sulfides is first order with respect to the sulfide and Mo(VI) but zero order in perborate. The uncatalysed reaction is first order in each the reductant and oxidant. Trichloroacetic acid enhances the oxidation rate. Oxidation of para-substituted. S -phenylmcrcaploacclic acids yielded a Hammett p of -0.54 at 293 K, indicating an electron-deficient sulfur atom in the transition state. 

Dichloroiodo)arenes may also be converted to (diacetoxyiodo)arenes upon treatment with mercuric acetate. This approach and also perborate oxidation of iodides were used for the preparation of some chiral l,l -binaphthyl derivatives [28]. 

The best known member among the various classes of these iodanes is undoubtedly [hydroxy(tosyloxy)iodo]benzene (HTIB), sometimes called Koser s reagent. It is prepared readily from (diacetoxyiodo)benzene and p-toluenesul-fonic acid monohydrate in acetonitrile. The same method using p-nitroben-zenesulfonic acid or 10-camphorsulfonic acid leads to the corresponding sul-fonyloxy analogs [41,42]. Of special interest are some iodanes of this type coming from a chiral ether. Their preparation was effected by direct oxidation with sodium perborate and the isolated diacetoxy derivatives were separately treated with p-toluenesulfonic acid in acetonitrile (Scheme 8) [43]. 

Hydroboration is not restricted to alkenes alkynes also react well to give vinyl boranes. These may be used directly in synthesis or oxidized to the corresponding enol, which immediately tautomerizes to the aldehyde. An example of this transformation is the conversion of 1-octyne into octanal by hydroboration with disiamylborane and oxidation with sodium perborate under very mild conditions. 

Steric effects were responsible for the complete diastereocontrol observed in the oxidation of various 6-halopenicillins by dimethyl dioxirane (DMD). Only one of the two possible diastereomeric sulfoxides has been obtained in each case23 (Table 1). Scheme 3 shows that perborate oxidation of optically active sulfide 16 affords, with moderate diastereoselectivity (78% de), the (f )-sulfoxide 17,24 designed as chiral ligand for catalytic asymmetric synthesis. 

Direct activation methods are not normally successful for the oxidation of alcohols using hydrogen peroxide. An advantage of this is that alcohols can often be used as solvents for other oxidations, which do not use direct activation methods. However, hydroxy ketals can be cleaved with aqueous hydrogen peroxide, and the ene-diol of L-ascorbic acid can be oxidized with sodium perborate.185 Under the conditions employed, it is likely that the active oxidant is free hydrogen peroxide rather than any boron species. 

Many heterocyclic bases can be oxidized to A-oxides with sodium perborate and acetic acid in the absence of metal catalysts.352 Use of a smaller excess of oxidant leads to diazo compounds.353 Aliphatic amines can be converted to nitroso products. Sodium perborate/acetic acid systems can also cleave hydra-zones, regenerating carbonyl compounds which have been protected by hydrazine formation.354... 

Rarely used oxidants with potential advantages as chemoselective or regioselective reagents include silylated forms of HOOH and peroxysulfuric acid, and the safe and inexpensive weak oxidant sodium perborate. Benzeneseleninic acid/30% hydrogen peroxide has been reported as a polystyrene-bound version, " as has peroxyarsenic acid. ... 

A comparative analysis of oxidants used for the preparation of Met(O) derivatives from the related N -protected amino acid (Table 1) indicates that sodium perborate is apparently the most convenient reagent, since only negligible amounts of the sulfones are formed. In all cases a heterogeneous mixture of the two sulfoxide diastereoisomers is obtained with an (S,SIR,R) ratio of ca. 1 in the case of the perborate oxidation. ... 

As an alternative, organoboranes can be oxidized with Na-perborate (NaB03 4 H20)" or with trimethylamine N-oxide (MejNO). Oxidation of trialkylboranes with pyridinium chlorochromate (PCC) leads directly to the corresponding carbonyl compounds. ... 

With acetic acid as solvent, sodium perborate oxidizes p-substituted derivatives of aniline to azobenzenes at temperatures of 35-60°. An example is formulated ... 

A number of anilines have been oxidized with the same reagent in AcOH (50-60 °C, 1.5-2 h) to afford nitroarenes in 47-92% yields (Scheme 118) ° . 4-Methoxy- and 4-cyanoanilines (618 and 619) underwent sodium perborate oxidation in AcOH to the corresponding nitroarenes 620 and 621 in 70 and 91% yields, respectively. 

Fig. 3. Oxidations with sodium perborate. Current Production > 106 t year 1 Major Uses Detergents, Antiseptic...

Diastereoselective hydrogenation of vinyl sulfones and sulfoxides. Hydrogenation of the vinyl sulfone 2 with the Rh catalyst 1 proceeds in 99% de to give 3. Similar hydrogenation of the corresponding sulfoxide provides 5, which on perborate oxidation gives the t/ireo-isomer of 3. Apparently the steric course of hydrogen-... 

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