Bouveault-Blanc reaction

Methods to transform ketones into alcohols are based on using of alkali metals as electron donors. One of these methods is the Bouveault-Blanc reaction A ketone is dissolved in an alcohol and boiled with an excess of sodium. Sometimes, a ketone-alcohol mixture is rapidly added to molten sodium. Sodium reacts with both ketone and alcohol. 

The reaction of esters with sodium in ethanol is referred to as the Bouveault-Blanc reaction. Prior to the discovery of complex metal hydrides, this reaction was the only method for the reduction of esters to alcohols. The diesters shown in Figure 17.59 produce a diol in this way. 

Although lactones may be reduced electrochemically or via Bouveault-Blanc reactions to produce diols, such reactions are more frequently used to prepare lactols. Both cathodic (Hg or Pb) and Na/Hg reduction are useful in the preparation of alditols from aldonic acid y-lactones. The reductions may be easily stopped at the intermediate aldose stage. ... 

Sodium metal in conjunction with a protic solvent such as an alcohol is sometimes used as a less expensive substitute for lithium aluminum hydride for reducing esters to alcohols in an industrial setting. This is the Bouveault-Blanc reaction. A modem version of this old reaction employs sodium-in-silica-gel (Na-SG), a safe fi ee-flowing powder, instead of the bulk metal (B. S. Bodnar, P. F. Vogt, J. Org. Chem. 2009, 74, 2598-2600) ... 

Benzilic acid rearrangement Benzoin reaction (condensation) Blanc chloromethylation reaction Bouveault-Blanc reduction Bucherer hydantoin synthesis Bucherer reaction Cannizzaro reaction Claisen aldoi condensation Claisen condensation Claisen-Schmidt reaction. Clemmensen reduction Darzens glycidic ester condensation Diazoamino-aminoazo rearrangement Dieckmann reaction Diels-Alder reaction Doebner reaction Erlenmeyer azlactone synthesis Fischer indole synthesis Fischer-Speior esterification Friedel-Crafts reaction... 

The Riihlmann modification (Bouveault-Blanc Condensation or Riihlmann Reaction) traps the dienolate as a TMS derivative. This protocol generally results in improved yields. 

Octanol has previously been prepared from ethyl caprylate by catalytic hydrogenolysis,21 and by the Bouveault-Blanc method using sodium and alcohol in toluene.22 Other preparative methods include the reaction between fi-hexylmagnesium... 

If the reaction is carried out in the presence of a proton donor, such as alcohol, simple reduction of the ester to the alcohol takes place (Bouveault-Blanc Reduction). 

The so-called acyloin condensation consists of the reduction of esters—and the reduction of diesters in particular—with sodium in xylene. The reaction mechanism of this condensation is shown in rows 2-4 of Figure 14.51. Only the first of these intermediates, radical anion C, occurs as an intermediate in the Bouveault-Blanc reduction as well. In xylene, of course, the radical anion C cannot be protonated. As a consequence, it persists until the second ester also has taken up an electron while forming the bis(radical anion) F. The two radical centers of F combine in the next step to give the sodium glycolate G. Compound G, the dianion of a bis(hemiacetal), is converted into the 1,2-diketone J by elimination of two equivalents of sodium alkoxide. This diketone is converted by two successive electron transfer reactions into the enediolate I, which is stable in xylene until it is converted into the enediol H during acidic aqueous workup. This enediol tautomerizes subsequently to furnish the a-hydroxyketone—or... 

The reduction of esters by sodium and alcohol (Bouveault-Blanc) is widely used. An alcoholic solution of the ester is added to a large excess of sodium under benzene or toluene. The use of absolute alcohol is essential otherwise an appreciable quantity of acid is produced by saponification. Straight-chain primary alcohols containing up to thirty-five carbon atoms have been made by the reduction of the corresponding esters with sodium sand and n-butyl alcohol. An improved technique based on the mechanism of the reaction is described. By this procedure a xylene solution of the ester and the reducing alcohol is added to molten... 

Alcohols will form metal salts. Thus treatment with sodium, potassium or magnesium leads to the evolution of hydrogen and the formation of the alkoxides (Scheme 2.11b). The liberation of hydrogen in this reaction is used in the Bouveault-Blanc reduction of ketones, esters and nitro compounds. 

This reaction, known as the Bouveault-Blanc reduction,... 

The hydrolysis of aphylline and of aphyllidine (XCV) gives aphyllinic acid (mp 214°) and aphyllidinic acid (mp 221°), respectively. Aphyllinic acid can be converted into sparteine by the following sequence of reactions esterification, Bouveault-Blanc reduction, chlorination, and cyclization with alkali 76). Aphylline and aphyllidine react with sodium amide in benzene solution to give the corresponding amides, XCVI and XCVII (77). 

Saturated ketones are reduced to the thermodynamically more stable alcohols in the Bouveault Blanc reduction by an almost identical mechanism. This old reaction has been largely superseded by the advent of complex metal hydrides like NaBH4 and LiAlH4, but it is still useful when the metal hydride gives the undesired, nonthermodynamic product. 

Addition of Sodium to Esters. When sodium is added to esters, different products are obtained, depending upon the solvents employed. In alcohol solution the Bouveault-Blanc reduction occurs and an alcohol is formed. In an inert solvent such as ether, acyloins are produced. These reactions are closely related and will be considered together. 

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