Reduction, of acetone

A general study of the reduction of acetone to pinacol. Calvert, India Rubber Rev. 26, No. 9, 48 (1926). 

Furthermore, it is now clear that organometallic compounds may be unstable intermediates in other electrode processes. Thus, the reduction of acetone at a series different metals in aqueous sulphuric acid has been studied (Sekine etal., 1965), and the products of controlled-potential electrolyses are shown in Table 3. The reduction of isopropanol or pinacol... 

Organic Yield (%) from the Reduction of Acetone at 1-375 V in Aqueous Sulphuric Acid... 

Mononuclear ruthenium complexes were found to be superior to carbonyl clusters during a comprehensive comparison of a variety of catalysts in the reduction of acetone [49]. Without solvent, most catalysts were highly selective, although the activity was quite low. The addition of water to the system vastly increased yields, in agreement with Schrock and Osborrfs observations into rhodium-catalyzed hydrogenations (Table 15.9) [41],... 

It is worth noting that finding a secondary a-deuterium KIE larger than the EIE is not unique. In fact, it has been found in several other reactions. For instance, Cleland and co-workers (Cook et al., 1980,1981 Cook and Cleland, 1981a,b) found unexpectedly large secondary a-deuterium KIEs in some enzymatic reactions for example, a secondary a-deuterium KIE of 1.22 for the reduction of acetone catalysed by yeast alcohol dehydrogenase and a KIE of 1.34 for the reduction of cyclohexanone catalysed by horse-liver dehydrogenase. 

Yeast alcohol dehydrogenase (YADH), catalysis of reduction by NADH of acetone formate dehydrogenase (FDH), oxidation by NAD of formate horse-liver alcohol dehydrogenase (HLAD), catalysis of reduction by NADH of cyclohexanone With label in NADH, the secondary KIE is 1.38 for reduction of acetone (YADH) with label in NAD, the secondary KIE is 1.22 for oxidation of formate (FDH) with label in NADH, the secondary KIE is 1.50 for reduction of cyclohexanone (HLAD). The exalted secondary isotope effects were suggested to originate in reaction-coordinate motion of the secondary center. 

Although acetone is used widely as an industrial solvent, nevertheless it has become the by-product of the acetone-butanol fermentation and there is always the fear of overproduction. There is thus a need for an extension of the industrial utilization of acetone. A possibility in this direction may be in its conversion into pinacol, the preparation of which has recently been improved by McHenry, Drum and O Connor. It is obtained together with isopropyl alcohol by electrolytic reduction of acetone under controlled conditions. Pinacol (LXVI) may be dehydrated to 2,3-dimethylbutadiene which can be converted into a synthetic rubber, or converted through pinacolone (LXVII) into neohexane... 

Following the reduction of acetone in isopropanol by means of a hydride the H NMR spectrum of the crude, isolated product reveals that the reaction has not completed. The integration curve of the remaining acetone corresponds to... 

The only practical method for the preparation of pinacol hydrate is the reduction of acetone and the procedure described above is a modification of that of Holleman.1 The more common reducing agents that have been used are magnesium amalgam,2 aluminum amalgam,3 sodium,4 and sodium amalgam.5 Electrolytic reduction has also been used.6 1 Rec. trav. chim. 25, 206 (1906). 

In the past, this field has been dominated by ruthenium, rhodium and iridium catalysts with extraordinary activities and furthermore superior enantioselectivities however, some investigations were carried out with iron catalysts. Early efforts were reported on the successful use of hydridocarbonyliron complexes HFcm(CO) as reducing reagent for a, P-unsaturated carbonyl compounds, dienes and C=N double bonds, albeit complexes were used in stoichiometric amounts [7]. The first catalytic approach was presented by Marko et al. on the reduction of acetone in the presence of Fe3(CO)12 or Fe(CO)5 [8]. In this reaction, the hydrogen is delivered by water under more drastic reaction conditions (100 bar, 100 °C). Addition of NEt3 as co-catalyst was necessary to obtain reasonable yields. The authors assumed a reaction of Fe(CO)5 with hydroxide ions to yield H Fe(CO)4 with liberation of carbon dioxide since basic conditions are present and exclude the formation of molecular hydrogen via the water gas shift reaction. H Fe(CO)4 is believed to be the active catalyst, which transfers the hydride to the acceptor. The catalyst presented displayed activity in the reduction of several ketones and aldehydes (Scheme 4.1) [9]. 

The FO approximation was introduced in 1952 when all calculations were done using the Hiickel method. In these conditions, the n frontier orbitals were also the chemically reactive MOs. Semi-empirical and ah initio calculations, which are frequently used now, take into account both o and n orbitals. With these methods, the orbitals to be considered in FO theory are not necessarily the formal frontier orbitals, i.e. the highest occupied and lowest unoccupied MOs Consider, for example, the reduction of acetone by LiAlH4. The chemically important MO is of course the Jt co of the ate complex, which is in fact the LUMO + 1. The formal LUMO is the empty s orbital of the lithium cation. 

Ethylenediamine-bisborane is a white crystalline solid which is quite stable on standing and can be stored at room temperature in a desiccator for several months. It evolves hydrogen slowly on warming and decomposes rapidly at about 90°C. The use of this compound for the reduction of acetone, acrolein, cinnamaldehyde, and acetyl chloride to the corresponding alcohols (isopropyl alcohol, allyl alcohol, cinnamyl alcohol, and ethyl alcohol) has been described.1 Its solubility characteristics and its thermal and hydrolytic stability have been reported.1-4... 

Dimethyl-2,3-butanediol (pinacol) (2.12) on treatment with H2SO4 generates 3,3-dimethyl-2-butanone, commonly known as pinacolone (2.13). Pinacol itself is produced by magnesium reduction of acetone, probably by way of a ketyl intermediate. 

This hydrazine is available by catalytic reduction of acetone azine. ... 

These media are essentially an extension of dilute solutions whereby the solute now comprises a significant fraction of the total volume. Nevertheless, the principle remains the same, namely to generate the required radicals. For example, one-electron reduction of the fullerene Cg4 has been effected in nitrogen-saturated toluene/2-propanol/acetone (8 1 1) [42]. Here the solvent primary radicals are converted to (CH3)2 C0H by reduction of acetone and oxidation of 2-propanol. 

The catalytic effect of the electrode material on the branching of an electrode reaction is most often apparent at cathodes with low overvoltage but may also be observed at materials with high hydrogen overvoltage. In the reduction of acetone in 6 N H2SO4 at a platinized platinum electrode, two independent paths are accessible One leads to propane and the other to isopropyl alcohol. The rate of formation of these two products depends on the voltage and on the history of the electrode. 

The electrochemical reduction of formaldehyde to the corresponding pinacol, dihy-droxyethane, has been closely examined as a possible technical scale process. Yields are very dependent on the choice of reaction conditions. Best results are obtained with a graphite cathode and sodium formate as electrolyte at 57°C [20]. The reduction of acetone to pinacol has also been examined from a technical point of view. Moderate yields of pinacol are obtained at a lead cathode in acid solution together with isopropanol and propane. The propane arises by hydrolysis of lead alkyl intermediates and under some conditions tetraisopropyllead is formed [21]. A pilot plant scale production of acetone... 

Phenylmagnesium bromide is incapable of homolysis, phenyl radicals being extremely unstable. Also, since the reduction of acetone is much less easy than the reduction of an aromatic ketone, such as benzophenone, the transfer of one single electron (as in a reduction reaction) from phenylmagnesium bromide to acetone is very unlikely when other reaction paths are available. A concerted reaction is such a path. 

Isopropyl alcohol may be prepared from propylene by the catalytic reduction of acetone, or by fermentation of certain carbohydrates. 

This hydrazine is available by catalytic reduction of acetone azine.1 Protection of carboxylic acids.2 The reagent reacts with carboxylic acid derivatives (the acyl chloride or mixed anhydride) to give a monoacylhydrazide, RCON(CHMe2)-NH(CHMe2). The derivatives are stable to both acids and bases. They are reconverted into carboxylic acids by selective oxidation, preferably with lead tetraacetate. The new method of protection has been used for penicillins. 

In the reduction of acetone to pinacol, magnesium amalgam is generated in situ by dropwise addition of a solution of 90 g. of mercuric chloride in 505 ml. of acetone to a suspension of 80 g. of magnesium turnings in 800 ml. of benzene. 

This section is concerned with radical dimerisations of this kind (22-23), mostly to make 1,2-difunctionalised compounds. Thus a 1,2-diol (24) could be made from two radicals (25) and this is indeed how it is made. The radicals (25) are generated by metal catalysed reduction of acetone. The product (24) is known as pinacol and the reaction is sometimes called pinacol reduction. The reaction works for most ketones, including enolisable ketones. 

A similar reaction has been observed for both the ionized and unionized isopropyl radical produced, either by reduction of acetone by e aq, or by oxidation of isopropyl alcohol in N20-saturated solution (8)... 

Pinacol was made by the Germans during the war in large quantities by the reduction of acetone with aluminium. It was converted by heating under pressure into dimethyl butadiene, CH2 = C.CH3.C.CH3. =CH2, which yielded a synthetic rubber when polymerized (49). 

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