Sodium hypochlorite secondary alcohols

In another procedure, oxidation is carried out in the presence of chloride ions and ruthenium dioxide [31]. Chlorine is generated at the anode and this oxidises ruthenium to the tetroxide level. The reaction medium is aqueous sodium chloride with an inert solvent for the alkanol. Ruthenium tetroxide dissolves in the organic layer and effects oxidation of the alkanol. An undivided cell is used so that the chlorine generated at the anode reacts with hydroxide generated at the cathode to form hypochlorite. Thus this electrochemical process is equivalent to the oxidation of alkanols by ruthenium dioxide and a stoichiometric amount of sodium hypochlorite. Secondary alcohols are oxidised to ketones in excellent yields. 1,4- and 1,5-Diols with at least one primary alcohol function, are oxidised to lactones while... 

Nickel(lll) oxide, prepared from a nickel(ii) salt and sodium hypochlorite, is used for the oxidation of alkanols in aqueous alkali [46]. Residual nickel(Ii) oxide can be re-activated by reaction with sodium hypochlorite. Nickel oxides have also long been used in the manufacture of the positive pole in the Edison nickel-iron rechargeable battery, now largely superseded by die lead-acid accumulator, and in the Jungner nickel-cadmium batteries used as button cells for calculators [47]. Here, prepared nickel oxide is pressed into a holding plate of perforated nickel. Such prepared plates of nickel(lli) oxide have been proposed as reagent for the oxidation, in alkaline solution, of secondary alcohols to ketones and primary alcohols to carboxylic acids [48]. Used plates can be regenerated by anodic oxidation. 

A convenient procedure for the oxidation of primary and secondary alcohols was reported by Anelli and co-workers (8,9). The oxidation was carried out in CH2CI2 with an aqueous buffer at pH 8.5-9.5 utilizing 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO, 1) as the catalyst and KBr as a co-catalyst. The terminal oxidant in this system was NaOCl. The major disadvantage of using sodium hypochlorite or any other hypohalite as a stoichiometric oxidant is that for each mole of alcohol oxidized during the reaction one mole of halogenated salt is formed. Furthermore,... 

Oxidation of CHOH (7, 337). Sodium hypochlorite solutions1 oxidize secondary alcohols dissolved in acetic acid to ketones in yields of 90-95%. Selective oxidation in the presence of a primary alcohol group is possible. The oxidation has been conducted, with suitable precautions, on a large scale.2... 

Although NaI04 or KI04 are the secondary oxidants used in the vast majority of cases in which alcohols are oxidized with catalytic Ru04, the employment of sodium hypochlorite (NaOCl),31 sodium bromate (NaBrOj )32 or Cl+, electrolytic-ally generated by oxidation of chloride ion,33 have also been reported. 

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... 

The very common TEMPO-mediated Anelli s protocol for the oxidation of alcohols, involving a biphasic CH2Cl2-water mixture containing catalytic TEMPO, or an analogue thereof, and sodium hypochlorite as a secondary oxidant, shows a great selectivity for the oxidation of primary alcohols in the presence of secondary ones9 and has found some use in Synthetic Organic Chemistry.10... 

In 1980, Stevens et al.10 reported that a plain solution of sodium hypochlorite, which is easily available as swimming pool chlorine , is able to efficiently oxidize secondary alcohols in a solution in acetic acid, while primary alcohols react very slowly. Two years later, this research team published11 a more detailed account on the ability of NaOCl/AcOH to perform the selective oxidation of secondary alcohols in the presence of primary ones. Stevens oxidant became one of the standard reagents for the selective oxidation of secondary alcohols.12... 

General Procedure for Selective Oxidation of Secondary Alcohols in Presence of Primary Alcohol, Using Stevens Protocol (Sodium Hypochlorite in Acetic Acid)... 

Sodium hypochlorite (household bleach) and acetic acid offers a very cheap and effective alternative to Jones reagent for the oxidation of secondary alcohols to ketones and has been widely used for the synthesis of ketones. 

Is there a more environmentally friendly reagent available to accomplish the oxidation of alcohols Recently, it has been shown that sodium hypochlorite (NaOCI) in acidic solution is an excellent reagent for the oxidation of secondary alcohols to ketones. Examples are shown in the following equations ... 

Primary and secondary alcohols are easily oxidized by a variety of reagents, including chromium oxides, permanganate, nitric acid, and even household bleach (NaOCl, sodium Oxidation hypochlorite). The choice of reagent depends on the amount and value of the alcohol. We of AI CO h OIS use cheap oxidants for large-scale oxidations of simple, inexpensive alcohols. We use the most effective and selective reagents, regardless of cost, for delicate and valuable alcohols. 

Many reagents are available to oxidize a simple secondary alcohol to a ketone. Most labs would have chromium trioxide or sodium dichromate available, and the chromic acid oxidation would be simple. Bleach (sodium hypochlorite) might be a cheaper and less polluting alternative to the chromium reagents. DMP and the Swem oxidation would also work. 

As mentioned before a PEG-supported TEMPO proved to be very efficient in the oxidation of 1-octanol to octanal not only with sodium hypochlorite, but also in combination with different terminal oxidants such as bis(acetoxy)iodobenzene and trichloroisocyanuric acid. This reaction could be extended to acyclic and cyclic primary and secondary alcohols with excellent results. It is remarkable that the PEG-supported TEMPO maintained the good selectivity for primary vs secondary ben-zylic alcohol oxidation typical of non-supported TEMPO. 

Barton oxidation was the key to form the 1,2-diketone 341 in surprisingly high yield, in order to close the five-membered ring (Scheme 38). The conditions chosen for the deprotection of the aldehyde, mercuric oxide and boron trifluoride etherate, at room temperature, immediately led to aldol 342. After protection of the newly formed secondary alcohol as a benzoate, the diketone was fragmented quantitatively with excess sodium hypochlorite. Cyclization of the generated diacid 343 to the desired dilactone 344 proved very difficult. After a variety of methods failed, the use of lead tetraacetate (203), precedented by work performed within the stmcmre determination of picrotoxinin (1), was spectacularly successful (204). In 99% yield, the simultaneous formation of both lactones was achieved. EIcb reaction with an excess of tertiary amine removed the benzoate of 344 and the double bond formed was epoxidized with peracid affording p-oxirane 104 stereoselectively. Treatment of... 

There is an alternative oxidant for secondary alcohols that is just as efflcientand much safer from an environmental standpoint 5.25% (0.75 M) sodium hypochlorite solution available in the grocery store as household bleach. The mechanism of the reaction is not clear. It is not a free radical reaction the reaction is much faster in acid than in base elemental chlorine is presumably the oxidant and hypochlorous acid must be present. It may form an intermediate alkyl hypochlorite ester, which, by an Ej elimination, gives the ketone and chloride ion. 

Sodium hypochlorite is used for the epoxidation of double bonds [659, 691] for the oxidation of primary alcohols to aldehydes [692], of secondary alcohols to ketones [693], and of primary amines to carbonyl compounds [692] for the conversion of benzylic halides into acids or ketones [690] for the oxidation of aromatic rings to quinones [694] and of sulfides to sulfones [695] and, especially, for the degradation of methyl ketones to carboxylic acids with one less carbon atom [655, 696, 697, 695, 699] and of a-amino acids to aldehydes with one less carbon [700]. Sodium hypochlorite is also used for the reoxidation of low-valence ruthenium compounds to ruthenium tetroxide in oxidations by ruthenium trichloride [701]. 

Hypochlorites are very good oxidizers of alcohols and are frequently selective enough to oxidize secondary alcohols in preference to primary alcohols see equations 288-291). Solutions of sodium hypochlorite in acetic acid react exothermically with secondary alcohols within minutes [693]. Calcium hypochlorite in the presence of an ion exchanger (IRA 900) oxidizes secondary alcohols at room temperature in yields of 60-98% [76 5]. Tetrabutylammonium hypochlorite, prepared in situ from 10% aqueous sodium hypochlorite and a 5% dichloromethane solution of tetrabutylammonium bisulfate, oxidizes 9-fluorenol to fluorenone in 92% yield and benzhydrol to benzophenone in 82% yield at room temperature in 35 and 150 min, respectively [692]. Cyclohexanol is oxidized to cyclohexanone by teit-butyl hypochlorite in carbon tetrachloride in the presence of pyridine. The exothermic reaction must be carried out with due precautions [709]. 

A general rule is that allylic alcohols are more readily oxidized than saturated secondary alcohols [975], and these, in turn, are more readily oxidized than saturated primary alcohols [681, 741, 1041, 1152], Ceric sulfate [741], ceric ammonium nitrate [741], chlorine [681], sodium hypochlorite [1152], and 2,3-dichloro-5,6-dicyano-p-benzoquinone [975] are successfully used for this purpose (equations 287-289). 

If a secondary alcohol is not easily oxidized by other methods the ruthenium(Vin) oxide catalyzed procedure is often recommended. As mentioned previously, this is a strong oxidation method which is not compatible with a number of functional groups. Sodium periodate usually serves as the stoichiometric oxidant, but sodium hypochlorite has also been used in the oxidation of secondary alcohols [94]. Because of the cheap oxidants and a straightforward work-up this reaction is well suited for large-scale oxidations [95]. The TEMPO procedure also employs a cheap stoichiometric oxidant and has been applied in the oxidation of 23 on a kilogram scale [87]. The TPAP-catalyzed method is a milder procedure and many functional groups are stable to these conditions. However, secondary alcohols are still oxidized to ketones in high yield with NMO as the co-oxidant [24]. 

An enhanced IPTC activity was observed for water-soluble /1-cyclodextrin-epichlor-ohydrin copolymers in the nucleophilic substitution reactions of alkyl bromides and sodium iodide [165]. However, in the hypochlorite-induced oxidation of 1-phenyl-1-propanol or benzyl alcohol in the presence of /1-cyclodextrin, the reactions were enhanced by lowering the pH of the aqueous phase rather than by the IPTC catalyst [166]. In contrast, the secondary alcohol was inert in aqueous hypochlorite solution maintained at high pH, even in the presence of the cyclodextrin. 

The stable, commercially available nitroxyl radical 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO) 51 is an excellent catalyst, in conjunction with a co-oxidant, for the oxidation of alcohols. The most popular co-oxidant is buffered sodium hypochlorite (NaOCl). Oxidation of the nitroxyl radical gives the oxoammonium ion 52, which acts as the oxidant for the alcohol to form the carbonyl product. Primary alcohols are oxidized faster than secondary and it is often possible to obtain high chemoselectivity for the former. For example, oxidation of the triol 53 gave the aldehyde 54, with no oxidation of the secondary alcohols (6.44). The use of TEMPO is particularly convenient for the oxidation of primary alcohols in carbohydrates, avoiding the need for protection of the secondary alcohols. 

Oxidation of alcohols is often aeeomplished conveniently by or via hypochlorites in sueh Ireatment of primary-seeondary diols, a selectivity of 1 7-20 is reached for the seeondary hydroxyl group. In general, sodium hypochlorite in acetic acid solution is used for this purpose (25). We obtained very good results, based on chlorine or trichloroisocyanuric acid (TCIA) in methanol in acid-buffered medium. The hy-droxyketone [7] can be formed reliably with a selectivity of 1 50-65. The improved selectivity is based on the use of the lowest convenient temperature and on the Promotion of the exchange of positive chlorine between primary and secondary alcohol positions (including from relatively stable methyl hypochlorite). 

The application of environmentally benign principles to laboratory-scale synthesis can be illustrated by revisiting the oxidation of alcohols. As noted in Section 15.9, an alternative to chromium (Vl)-based oxidants is the Swern oxidation. Another method is one that uses sodium hypochlorite. Aqueous solutions of sodium hypochlorite are available as swimming-pool chlorine, and procedures for their use in oxidizing secondary alcohols to ketones have been developed. 

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