Ester, manganate

The intermediate formed in the oxidation of alkenes by permanganate ion is considered a cycHc manganate(V) ester (92). Investigations have suggested that manganate(V) intermediates play a significant role in virtually all permanganate oxidation reactions. It is therefore the further reactions of the... 

At pH 13 the final products are manganate and cw-diol. The observation of a large degree of transfer of 0 from labelled MnO into oleate ion at pH 12 suggests formation of a cyclic ester, viz. 

Another reaction in which the cleavage of a carbon-hydrogen bond is important is the bromination of ketones. In the bromination of ethyl acetoacetate and 2-carboethoxycyclopentanone, it was shown that multivalent cations are catalysts. In the latter reaction, cupric, nickelous, lanthanum, zinc, plumbous, manganous, cadmium, magnesium, and calcium ions were effective (45). One can interpret the effect of the metal ion in terms of its catalysis of the proton transfer from the ester to a base, whether the reaction is carried out in dilute hydrochloric acid solution (acid-catalyzed bromination) or in acetate buffer (base-catalyzed bromination). 

The preparation of ketones by dehydrogenation of secondary alcohols over zinc and copper catalysts and the decarboxylation condensation of acids over manganous oxide or thoria have been adequately covered by standard reference books on catalysis. However, the more complete but equally serviceable catalytic syntheses involving either an aldol or a Tischenko ester type of condensation have been virtually ignored. 

A wide variety of substituted y-butyrolactones can be prepared directly from olefins and aliphatic carboxylic acids by treatment with manganic acetate. This procedure is illustrated in the preparation of 7-( -OCTYL)-y-BUTYROLACTONE. Methods for the synthesis of chiral molecules are presently the target of intensive investigation. One such general method developed recently is the employment of certain chiral solvents as auxiliary agents in asymmetric synthesis. The preparation of (S.SM+H, 4-BIS(DIMETHYLAMINO)-2,3-DIMETHOXY-BUTANE FROM TARTARIC ACID DIETHYL ESTER provides a detailed procedure for the production of this useful chiral media an example of its utility in the synthesis of (+)-(/ )-l-PHENYL-l-PEN-TANOL from benzaldehyde and butyllithium is provided. 

Mechanism The Mn02 oxidation reaction is believed to proceed by adsorption of alcohol on Mn02 followed by coordination of both alcohol and Mn02- Electron transfer then produces the radical, and Mn(IV) is reduced to Mn(III). Another electron transfer is followed by the release of adsorbed carbonyl product with the loss of water from Mn(OH)2 (Scheme 7.4). An ionic mechanism is also proposed for this oxidation which involves the formation of manganate ester. ... 

Most of the reported work on the kinetics of catalysed polycondensation by transesterification is quite recent and in the main deals with the preparation of PET, though related work on other esters from ethylene glycol has been reported. Reinisch et al. [34] found that the melt polycondensation leading to poly(ethylene sebacate) in 3—4 mm films under vacuum, with manganous acetate as catalyst, was second order from p = 0.70 to p = 0.97. Rate coefficients are listed in Table 5 for this reaction, for the formation of poly(ethylene sebacate-co-terephthalate) and for PET. 

Dihydrofumnes. Dihydrofuranes are obtained in fair to high yield by reaction of readily enolizable ketones (/3-diketones, /3-keto esters) with olefins in the presence of 2 eq. of manganic acetate. The reaction is considered to involve generation and oxidation of free radicals. 

Diketones. The reaction of enol esters with ketones at 50-70° in the presence of manganic acetate (2 eq.) leads to 1,4-diketones in moderate yields ... 

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