Manganese complexes ketones

Ketones are resistant to oxidation by dioxygen in aqueous solutions at T= 300-350 K. Transition metal ions and complexes catalyze their oxidation under mild conditions. The detailed kinetic study of butanone-2 oxidation catalyzed by ferric, cupric, and manganese complexes proved the important role of ketone enolization and one-electron transfer reactions with metal ions in the catalytic oxidation of ketones [190-194],... 

Aryl alkyl ketones (e.g. 161) can be converted to amides (e.g. 162), with a loss of the alkyl group, by reaction with a carbodiimide. This unusual C -C arbonyi single-bond cleavage is catalysed by manganese complexes such as [HMn(CO)4l3 or Mn2(CO)io-Aryl isocyanates, Ar-N=C=0, are mechanistically implicated, as the reaction can also be carried out using such isocyanates, and indeed, two isocyanate molecules can be converted to the corresponding carbodiimide using either catalyst. ... 

Epoxidation of olefins was catalyzed by the ruthenium(II) complex of the above perfluorinated y3-diketone in the presence of 2-methylpropanal (Scheme 50). Unfunctionalized olefins were epoxidized with a cobalt-containing porphyrin complex, and epoxidation of styrene derivatives was catalyzed by chiral salen manganese complexes (248) (Scheme 50). In the latter case, chemical yields were generally high, however, the products showed low enantiomeric excess with the exception of indene (92% ee). [Pd(C7Fi5COCHCOC7Fi5)2] efficiently catalyzed the oxidation of terminal olefins to methyl ketones with f-butylhydroperoxide as oxidant in a benzene-bromoperfluoro-octane solvent system (Scheme 50). In all these reactions, the product isolation and efficient catalyst recycle was achieved by a simple phase separation. 

Manganese(III) palmitate was found to be a selective catalyst for the conversion of dialkyl ketones to carboxylic acids at temperatures of 110 or greater [276]. A single carboxylic add could be formed from synunetrical ketones [276]. The ease with which manganese complexes convert aldehydes to carboxylic acids (Section 13) is utilized in this conversion. 

Anionic Additions to Aldehydes. The addition of l,3-bis(silyl)-propenes to aldehydes and ketones to yield the vinyl silyl alcohol was explored. This was done using TBAF and good to excellent yields were achieved (eq 11). A further extension of this work was the addition of the (l,3-bis(silyl)allyl)lithium to ketones and aldehydes (eq 12). In this reaction, the substituted silyl diene was isolated in moderate to good yields. These substrates were then explored as ligands for both iron and manganese complexes. 

Reactions 33 and 35 constitute the two principal reactions of alkyl hydroperoxides with metal complexes and are the most common pathway for catalysis of LPOs (2). Both manganese and cobalt are especially effective in these reactions. There is extensive evidence that the oxidation of intermediate ketones is enhanced by a manganese catalyst, probably through an enol mechanism (34,96,183—185). 

An electron-deficient manganese(III) porphyrin complex was reported to catalyze the oxidation of alkanes by PhI(OAc)2 in mixed [BMIM]PF6/CH2Cl2 at room temperature (230). Cyclic alkanes were oxidized to secondary alcohols and ketone. A highly active and short-lived intermediate, Mn = O, was observed in the ionic liquid, whereas in CH2CI2 the same reaction gave only a less-active intermediate, Mn " = O. 

Taylor and Flood could show that polystyrene-bound phenylselenic acid in the presence of TBHP can catalyze the oxidation of benzylic alcohols to ketones or aldehydes in a biphasic system (polymer-TBHP/alcohol in CCI4) in good yields (69-100%) (Scheme 117) °. No overoxidation of aldehydes to carboxylic acids was observed and unactivated allylic alcohols or aliphatic alcohols were unreactive under these conditions. In 1999, Berkessel and Sklorz presented a manganese-catalyzed method for the oxidation of primary and secondary alcohols to the corresponding carboxylic acids and ketones (Scheme 118). The authors employed the Mn-tmtacn complex (Mn/168a) in the presence of sodium ascorbate as very efficient cocatalyst and 30% H2O2 as oxidant to oxidize 1-butanol to butyric acid and 2-pentanol to 2-pentanone in yields of 90% and 97%, respectively. This catalytic system shows very good catalytic activity, as can be seen from the fact that for the oxidation of 2-pentanol as little as 0.03% of the catalyst is necessary to obtain the ketone in excellent yield. 

Ojima and co-workers first reported the RhCl(PPh2)3-catalyzed hydrosilylation of carbonyl-containing compounds to silyl ethers in 1972.164 Since that time, a number of transition metal complexes have been investigated for activity in the system, and transition metal catalysis is now a well-established route for the reduction of ketones and aldehydes.9 Some of the advances in this area include the development of manganese,165 molybdenum,166 and ruthenium167 complex catalysts, and work by the Buchwald and Cutler groups toward extension of the system to hydrosilylations of ester substrates.168... 

A catalytic route using a manganese (III) complex has been developed for a-hydroxylation of ketones avoiding the use of water or a protic solvent mixtures of a-hydroxyketones and their silyl derivatives were formed in excellent yield. By using a chiral pyrrolidine-based manganese (III) complex as catalyst, asymmetric oxidation was effected, with enantiomeric excess varying from 14 to 62% [30], Another kind of a-functionalized ketones resulted from silyl enol ethers which after the addition of IOB.BF3 were treated with triethyl phosphite a-ketophosphonates were obtained in this way [31] ... 

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