Bouveault-Blanc method

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... 

Lithium aluminum hydride shows much promise for the preparation of f>a/o and a//feoxy alcohols, although the Bouveault-Blanc method is satisfactory for the latter. 

Paquette and Nelson found this combination superior to the Bouveault-Blanc method for the selective reduction of the ester acid (1). Small portions of sodium... 

Methods Primarily of Historical Interest. In the Bouveault-Blanc deduction (79,80) phenylacetic ester is reduced with sodium and alcohol to... 

Naturally occurring fatty alcohols used in the fragrance industry are produced principally by reduction of the methyl esters of the corresponding carboxylic acids, which are obtained by transesterification of natural fats and oils with methanol. Industrial reduction processes include catalytic hydrogenation in the presence of copper-chromium oxide catalysts (Adkins catalysts) and reduction with sodium (Bouveault—Blanc reduction). Unsaturated alcohols can also be prepared by the latter method. Numerous alcohols used in flavor compositions are, meantime, produced by biotechnological processes [11]. Alcohols are starting materials for aldehydes and esters. 

Desulfonylation of a-sulfonylacetates. Desulfonylation of these substrates is not satisfactory by the usual methods (Zn-HOAc, Raney Ni-C,H5OH, sodium amalgam), but can be conducted in 70-75% yield with sodium-ethanol in THF (modified Bouveault-Blanc reduction). The substrates (2) are obtained by Wolff rearrangement of a-acyl-a-benzyl-sulfonyldiazomethanes (1).1... 

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 first commercial production of fatty alcohols in the 1930 s employed a sodium reduction process (Bouveault-Blanc) (2). However, the high usage (4 mol/mol alcohol) of expensive sodium soon led to replacement of this method of reduction by catalytic hydrogenation. 

This important fragrance material probably was introduced in commercial perfumery during the first decade of the twentieth century with the discovery of the Bouveault-Blanc reduction of esters by sodium and an alcohol (10). This is the first of several methods of preparation shown in Figure 16. Large quantities of phenylethyl alcohol were made by sodium reduction of butyl phenylacetate in normal butanol. The basic raw materials were readily available at low cost from benzyl chloride, sodium cyanide and fermentation butanol. 

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. 

The synthesis of bufotenine itself followed closely upon the proof of its structure. Hoshino and Shimodaira reduced the ethyl ester of 5-ethoxy-indole-3-acetic acid by the Bouveault-Blanc procedure to the corresponding primary alcohol, which was treated with phosphorus tribromide and then dimethylamine, to give the ethyl ether of bufotenine, which was demethylated with aluminum chloride (130). In a later synthesis, 2,5-dimethoxybenzyl cyanide (XXIII) was alkylated by Eisleb s method with dimethylaminoethyl chloride in the presence of sodamide to give l-(2,5-dimethoxyphenyl)-3-dimethylaminopropyl cyanide (XXIV), which was then hydrogenated over Haney nickel to yield 2-(2,5-di-methoxyphenyl)-4-dimethylaminobutylamine (XXV R = Me). De-methylation of this with hydrobromic acid, followed by oxidation of the product (XXV R = H) with potassium ferricyanide yielded bufotenine (XIX) via the related quinone (109). 

Optically active esters in which the activity is due to asymmetry of the a-carbon atom ate racemized by the Bouveault-Blanc and catalytic hydrogenation procedures. The optically active alcohols may be prepared by the addition of small pieces of sodium to a stirred mixture of an ethereal solution of the ester and aqueous sodium acetate at 0°. A slight acidity is maintained by periodic additions of acetic acid (Prin s method).An asymmetric center in the alpha position to a carboxyl group is not racemized by lithium aluminum hydride. ... 

Both the Bouveault-Blanc and catalytic hydrogenation proceduresare popular methods for the preparation d dials from esters of dibasic acids. The reduction of malonic esters, /3-keto esters, and /3-hydroxy esters by the usual catalytic hydrogenation procedure results in extensive bydrogenolysis of the carbon chain to give lower-molecular-weight alcohols. However, with relatively large amounts of catalyst... 

The desirable fragmentation (A) to give the alkyl radical represents a viable method for overall deoxygenation, providing that alternative processes involving O—X fission (B), or H-abstraction (C) or net two-electron reduction (D the Bouveault-Blanc reduction of esters, for example) followed by O— fission, can be minimized. Conditions have been established which cause (A) to be the dominant process for X = C, P and S this section will compare the merits of these processes for alcohol deoxygenation. 

Oleyl alcohol occurs naturally in fish oils. Synthetically, it can be prepared from butyl oleate by a Bouveault-Blanc reduction with sodium and butyl alcohol. An alternative method of manufacture is by the hydrogenation of triolein in the presence of zinc chromite. 

Protection.—Alkyl ester protection of alcohols is normally removed by methods such as base hydrolysis or reduction with LiAlH4. It has now been shown that dissolving-metal reduction of the Bouveault-Blanc type has value in this field [equation (7)] and allows recovery of primary and secondary alcohols from their... 

Small portions of Na added to a rapidly stirred soln. of trans-fi-(2-csitbo-methoxycyclohexane) propionic acid in liq. NHg and abs. ethanol, a little more ethanol finally added to decompose remaining Na, stirring continued until most of the NHg has evaporated, water added, acidified with HCl, extracted with ether, and the resulting crude hydroxy acid distilled in vacuo crude trans-3-oxa-4-oxobicyclo[5.4.0]undecane. Y 71.7%.— The above selective reduction method is superior to the Bouveault-Blanc procedure and nearly theoretical quantities of the hydroxy acid have been obtained. L. A. Paquette and N. A. Nelson, J. Org. Chem. 27, 2272 (1962). 

Na added all at once with vigorous stirring and some initial cooling to a mixture of ethyl hydrocinnamate, ethanol, phenol, and some quinoline, heated in an oil bath at 150°, then the temp, raised to 170° until the Na has disappeared after 15 min. phenylpropyl alcohol. Y 90%.—Similarly at 170-230° Ethyl L-leucinate —leucinol. Y 67%.—This method gives higher yields of amino-alcohols from amino esters with unprotected amino groups than the original Bouveault-Blanc procedure. F. e., also without addition of quinoline, s. W. Enz,. Helv. U, 206 (1961). 

Reduction of esters of monobasic acids with sodium and absolute ethyl alcohol (method of Bouveault and Blanc), for example ... 

This reaction was first reported by Bouveault and Blanc in 1903, and was further extended by Bouveault and Locquin. It is the synthesis of symmetrical a-hydroxy ketones via the reductive condensation of esters in an inert solvent in the presence of sodium. Since symmetrical a-hydroxy ketones, the aliphatic analogs of benzoins, are generally known as acyloins, the formation of a-hydroxy ketones from esters is simply referred to as acyloin condensation. In a few cases, it is also referred to as acyloin reaction." For the individual acyloin, the name is derived by adding the suffix oin to the stem name of corresponding acid, e.g., acetoin prepared from acetate. The most common method used to make acyloin is the reductive condensation of aliphatic esters with sodium in inert solvents, such as ether, xylene or even in liquid NH3 The yield of this reaction can be greatly improved when trimethylchlorosilane presents." " Intromolecular acyloin condensation from aliphatic diesters affords cyclic ketones of different ring sizes. 

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