Allyl manganese reagent

Chem. Lett. 1983,1237. (b) Use of manganese for the preparation of allylic manganese reagent, see Hiyama, T. Obayashi, M. Nakamura, A. 

An allyl Grignard reagent also adds to the triple bond of the alkyl ether of a homopropargylic alcohol to give the monoallylated products with high regio- and stereoselectivities in the presence of a catalytic amount of manganese salt [11] (Scheme 7-8). 

Allylic acetoxylation with palladium(II) salts is well known however, no selective and catalytic conditions have been described for the transformation of an unsubstituted olefin. In the present system use 1s made of the ability of palladium acetate to give allylic functionalization (most probably via a palladium-ir-allyl complex) and to be easily regenerated by a co-oxidant (the combination of benzoquinone-manganese dioxide). In contrast to copper(II) chloride (CuClj) as a reoxidant,8 our catalyst combination is completely regioselective for allcyclic alkenes with aliphatic substrates, evidently, both allylic positions become substituted. As yet, no allylic oxidation reagent is able to distinguish between the two allylic positions in linear olefins this disadvantage is overcome when the allylic acetates are to... 

In comparison with manganese dioxide, the DDQ reagent has several advantages for the oxidation of allylic alcohols. The quinone method is more reproducible only one equivalent of oxidant need be added and generally fewer side reactions are observed. On the other hand, the workup of DDQ reactions often requires chromatography and in the simpler cases lower isolated yields may be realized. 

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 ... 

Oxidation of sensitive divinyl alcohol 20 to dienone 4 is achieved by treatment with activated manganese dioxide. Commercially available active Mn02 21 is a synthetic nonstoichiometric hydrated material. This reagent provides mild conditions for oxidation of allylic, propargylic, and benzylic alcohols.10... 

The next important reaction is a Michael addition so the alcohol must first be oxidized to a ketone. As it is an allylic alcohol, it can be oxidized by manganese dioxide. The ring is further flattened as three atoms are now trigonal. But-3-enyl Grignard reagent is next added with Cu(I)... 

Manganese dioxide is a reagent that oxidizes only allylic or benzylic hydroxyl groups to ketones,... 

This reagent can be of value not only for its inherent chemoselectivity, but also because of the mild conditions under which oxidation occurs. For example the cyclohexylideneacetaldehydes (2) can be produced by manganese dioxide oxidation of the allylic alcohols despite the instability of (2) to air, acids and bases. Manganese dioxide is known to cleave 1,2-diols, and can cause oxidative rearrangement to... 

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