Sodium bromate secondary alcohols

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. 

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... 

Both, sodium bromite (NaBr02)51 and sodium bromate (NaBr03)52 are able to carry out selective oxidations of secondary alcohols in the absence of an added catalyst under properly devised experimental conditions. 

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). ... 

Ceric ammonium nitrate or ceric sulfate is used to oxidize saturated and unsaturated secondary alcohols to ketones. The ceric salts are used only in catalytic amounts with sodium bromate as a reoxidant (equation 241) [741]. 

Secondary alcohols are oxidized in preference to primary alcohols also by sodium bromate in the presence of catalytic amounts of ceric ammonium nitrate or ceric sulfate [741]. 

A very efficient method for the oxidation of secondary alcohols to ketones makes use of sodium bromate in the presence of ruthenium dioxide. Quantitative yields are obtained in 15 min at 25°C. Pulsed irradiation, with a 20% duty cycle, was used in addition to stirring. It appears that the sonochemical rate increase is due to two factors the acceleration of the oxidation of ruthenium dioxide to the actual reactive species ruthenium tetroxide, and the very efficient ultrasonic emulsification of the biphasic carbon tetrachloride-water system. 

One of the few disadvantages of CAN lies in the quantity of material sometimes required to oxidize alcohols in addition, such processes may not be as systematic or consistent as other methods. However, both ceric ammonium sulfate and CAN have been used as catalysts in the sodium bromate oxidation of secondary alcohols to ketones (Tomioka et al., 1982). 

Sodium bromate in presence of CAN or CAS is an effective reagent for the oxidation of secondary alcohols into the corresponding ketones (Tomioka et al., 1982 Kanemoto et al., 1986). For instance cyclododecanol is oxidized in 98% yield to cyclododecanone, and bor-neol is oxidized in 77% yield into camphor. Primary alcohols are not affected, so that this is a useful methodology for the oxidation of secondary alcohols in presence of primary ones. The presence of a double bond in the substrate, even at a position far way from the sec-... 

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