Bouveault reaction

The non-ultrasonic Bouveault reaction suffers from numerous side reactions. 

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Disubstituted formamides can give addition of 2 mol of Grignard reagent. The products of this reaction (called Bouveault reaction) are an aldehyde and a tertiary amine.The use of an amide other than a formamide can give a ketone instead... 

Extensions of the use of ultrasound in lithiation reactions have been profitable for a variety of reactions. The Bouveault reaction for the synthesis of aldehydes [Eq. (40)] suffers from side reactions and low yields. 

The Bouveault reaction is the preparation of an aldehyde by a one pot reaction between an organic halide and lithium metal in dimethylformamide. Ultrasound has been found to markedly enhance this reaction when it is performed in tetrahydrofuran [93]. Use of an ultrasonic bath at 10-20 °C affords short reaction times of between 5 and 15 min and generates yields in the range 70-88%. Using this methodology the conversion of 1-bromobutane to pentanal (88%) can be achieved in only 5 minutes. This must be contrasted with the yield of less than 10 % which is obtained under the normal stirred conditions in the same time period. This result confirms that the effect of irradiation goes beyond mere agitation (Eq. 3.11). 

Formylation of an alkyllithium (1, 280).1 Formylation of an alkyllithium or a Grignard reagent with DMF (Bouveault reaction) is generally unsatisfactory because of side reactions. However, sonication of the mixture of an alkyl or aryl halide, lithium, and DMF substantially improves the rate and the yield. The method is applicable to primary, secondary, and tertiary bromides or chlorides. Typical yields are in the range 65-85%. 

This type of reaction with A N-disubstituted formamides, giving aldehydes, was an early application of Grignard reagents, sometimes known as the Bouveault reaction [A]. Dimethylformamide and N-methylformanilide, PhN(Me)CHO, have been most commonly used, but more recently iV-formylpiperidine and 2-(/V-formylmethylamino)pyridine have been recommended examples are listed in Table 6.5, and a recent example of the traditional procedure follows. It should be noted that these reactions are subject to a number of side-reactions [A]. One useful one is the formation of enamines by elimination from the initial adduct [9] ... 

Also known as the Bouveault reaction. Reduction of esters to the corresponding alcohols using sodium in an alcoholic solvent. 

The title aldehyde was prepared as a hydrate by a modified Bouveault reaction. This procedure is usually carried out with magnesium or lithium, and sonication greatly enhances its yields. 0 In the present case, optimal results are obtained with an aluminum-tin couple. 

Sonication of aryl halides with lithium with low intensity ultrasonic gives organolithium reagents. These are used in Bouveault reaction giving higher yields of aldehydes (Scheme 27) than the traditional methods." ... 

Problem 10.8. In Scheme 10.40, the Bouveault reaction, two different results are obtained. Using the original literature (reference given) or any other source, attempt to justify the outcome. 

Turning their attention to the Bouveault reaction, Luche et al. found that aldehydes could be generated from alkyl halides in a one-pot reaction (Scheme 31). 

Luche et al. have since extended the scope of these reactions by using formamides to direct 6 r /io-lithiation of substituted benzenes, thus generating the 6 r / 6 -dialdehyde (6) from monohalogenated benzene via a double Bouveault reaction [97, 98] (Scheme 33). 

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