Manganese dioxide active, preparation

Nickel peroxide is a solid, insoluble oxidant prepared by reaction of nickel (II) salts with hypochlorite or ozone in aqueous alkaline solution. This reagent when used in nonpolar medium is similar to, but more reactive than, activated manganese dioxide in selectively oxidizing allylic or acetylenic alcohols. It also reacts rapidly with amines, phenols, hydrazones and sulfides so that selective oxidation of allylic alcohols in the presence of these functionalities may not be possible. In basic media the oxidizing power of nickel peroxide is increased and saturated primary alcohols can be oxidized directly to carboxylic acids. In the presence of ammonia at —20°, primary allylic alcohols give amides while at elevated temperatures nitriles are formed. At elevated temperatures efficient cleavage of a-glycols, a-ketols... 

Manganese dioxide has been nsed to carry out a range of chemical oxidations, and is the reagent of choice for the oxidation of allylic alcohols (Hndlicky 1990). There are several methods for its preparation that may acconnt for differences in its activity. Although it has seldom been exploited for the oxidation of contaminants, two widely different applications have been described ... 

This photoaffinity labelling analogue of all-fraws-retinal, 95b, has been tritium labelled80 by reduction of unlabelled aldehyde 95a with [3H]-NaBH4 and subsequent oxidation of the obtained tritium-labelled retinol with activated manganese dioxide. The product 95b (specific activity 38.3 mCimmol-1) has been isolated by preparative TLC (equation 36). 

Chemical manganese dioxide (CMD). This form of Mn02 is used for batteries it is available from I. C. Sample office (Cleveland, Ohio, 44101). Shioiri et al. report it is superior to commercial activated Mn02 (Aldrich) and more convenient than freshly prepared activated Mn02 for dehydrogenation of 2-(l-ami-noalkyl)thiazolidine-4-carboxylic acids to the corresponding thiazoles (thiazole amino acids). 

Silica reinforced rubber, 22 703 Silica sheets, 22 383-385 Silica-silane system, 22 377-378 Silica sol-gel fiber processing, 23 80 Silica sols, 22 383, 473-474 applications of, 22 394 modification of, 22 393-394 preparation of, 22 392-393 properties of, 22 391-392 purification of, 22 393 Silica, solubility in steam, 23 212-213 Silica-supported activated manganese dioxide, 76 568... 

Among the oxidative procedures for preparing azo compounds are oxidation of aromatic amines with activated manganese dioxide oxidation of fluorinated aromatic amines with sodium hypochlorite oxidation of aromatic amines with peracids in the presence of cupric ions oxidation of hindered aliphatic amines with iodine pentafluoride oxidation of both aromatic and aliphatic hydrazine derivatives with a variety of reagents such as hydrogen peroxide, halogens or hypochlorites, mercuric oxide, A-bromosuccinimide, nitric acid, and oxides of nitrogen. 

The earliest methods for preparing cyclic a-diazo ketones involved the oxidation of the monohydrazones prepared from a-diketones, generally using mercuric oxide.7,8 Recent modifications of this procedure include the use of calcium hypochlorite in aqueous sodium hydroxide or activated manganese dioxide as oxidants.1 The latter reagent, especially, hoc ms preferable to mercuric oxide. The base-catalyzed decomposition of tile monotosylhydrazoneH of a-diketones has been... 

Active manganese dioxide was used by Canonica in 19472 for the oxidation of oximes into nitrocompounds before the seminal publication of Ball et al. on the oxidation of vitamin A (76). Canonica prepared active manganese dioxide by reacting MnCb with KMn04. In fact the oxidation power of precipitated manganese dioxide is known since the 1870 s.3... 

Because of the time-consuming preparation of Attenburrow active manganese dioxide, the use of a number of more readily available types of active Mn02 was proposed. These include employing ... 

The preparation of an active manganese dioxide/charcoal catalyst has been described.23 t The determination of the extent of oxidation by measurement of i.r. absorption at 3 / n has been described.26... 

The reaction conditions for FDAM labeling were optimized for cellulose to fit into the usual activation protocol prior to dissolution in DMAc/LiCl (9%). FDAM can be prepared in the GPC eluant DMAc from 9f/-fluorcn-2-yl-carboxaldehyde via its hydrazone by oxidation with excess manganese dioxide [78]. 

Gemeay AH, Nishiya H, Kuwabata S, Yoneyama H. Chemical preparation of manganese dioxide/poly-pyrrole composites and their use as cathode active materials for rechargeable lithium batteries. J Electrochem Soc 1995 142 4190-4195. 

The bifunctional cyclopropane 156 was also prepared by modified Simmons-Smith cyclopropanation 85) of 2-trimethylsilyl-2-propen-l-ol 157 84) followed by oxidation of the cyclopropylcarbinol 158 with activated manganese dioxide 88 >, in 72% overall yield, Eq. (50) 86,89). Coupling of the aldehyde 156 with 2,6-dimethylcyclohexenone 159 90) induced by the low valent titanium reagent from TiCl3 and zinc-copper couple (or lithium metal) provided the silylated cyclopropyldiene 160, in 50-60% yield, Eq. (51) 89 91>. 

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