Barbier-Grignard reactions

In 1991, Whitesides etal. reported the first application of aqueous medium Barbier-Grignard reaction to carbohydrate synthesis through the use of tin in an aqueous/organic solvent mixture (Eq. 8.48).106 These adducts were converted to higher carbon aldoses by ozonolysis of the deprotected polyols followed by suitable derivatization. The reaction showed a higher diastereoselectivity when there was a hydroxyl group present at C-2. However, no reaction was observed under the reaction conditions when there was an /V-acctyl group present at the C-2 position. 

Barbier-Grignard reaction in water is very good (Li et al., 1996)... 

In the Barbier-Grignard reaction (Figure 12.12), the protection—deprotection sequence can be avoided and the products isolated by simple phase separation (rather than by distillation of an organic solvent). This modification involves the use of zinc instead of magnesium to form the organometallic intermediate (see Li and Chan, 1997). 

Styrene is an important olefinic substrate in Heck reactions a styrene carrying an alkoxysilyl moiety should open up a more convergent approach to the synthesis of the title compounds. Silane 15 was prepared via Barbier-Grignard reaction of p-bromostyrene with triethoxymethyl silane [21]. 

These simple and well-known reactions of inorganic chemistry are paralleled in organic chemistry by the Wiirtz and Fittig syntheses and the Barbier-Grignard reaction. The Wiirtz and Fittig syntheses may be formulated in most general terms as follows ... 

In these reactions, only the initial and final substances have been indicated. It is possible that the actual mechanism of the reaction is not so simple and that it takes place in several stages. Evidence for this view is to be found in an analogous reaction, in which magnesium is used in place of sodium. This reaction can be used in a great number of syntheses and is generally known as the Barbier-Grignard reaction. The ordinary formulation is as follows ... 

A reaction of this kind might be involved in the Barbier-Grignard reaction with the formation of salicylic acid from phenol, etc., without considering the intermediate products, but only the compositions and structures of the initial and final substances. The change involves the reduction of the carbon of the carbon dioxide and the oxidation of one of the carbon atoms of the benzene. It is exactly the same change as was shown in reaction (116) in the formation of methane and carbon dioxide from acetic acid which was shown to be an oxidation-reduction reaction. 

Chain-extended Sugars - The application of indium- and tin-mediated Barbier-Grignard reactions in aqueous solutions to the chain-extension of... 

The application of indium- and tin-mediated Barbier-Grignard reactions in aqueous solution to the chain extension of unprotected sugars has been reviewed. Some C-5 variants of iV-acetylneuraminic acid have been prepared by the indium-mediated addition of ethyl oc-(bromomethyl)acrylate to variously N-substituted mannosamines," and similar chemistry using (bromomethyl)vinyl phosphonate has led to the phosphonate analogue 12. The reaction of O-protected aldono-1,4- and -1,5-lactones with (2-bromomethyl)-acrylate or -acrylonitrile or 2-bromobutyrolactone mediated by samarium diodide led to chain-extended ulosonic acid derivatives." ... 

Name of the One-step Procedure. Early publications in this new field of organic chemistry reveal a bitter rivalry over priority and eponimy between the stu-dent/assistant Grignard (Nobel-prize winner 1912) and the teacher/head-of-the-department Barbier. Several modern historians have come to the conclusion [29] that the most reasonable name for this step-wise procedure would have been Barbier-Grignard reaction. 

The most systematic name would be the one in which the procedure is made clear to the reader such as one-pot reaction (e.g. in [30] and [31]) or one-flask reaction, in situ reaction [32], one-step reaction [33], etc. and such names are often encountered. However more often names such as modified) Wagner-Saytzejf reaction, Saytzeff reaction, Barbier-Grignard reaction [29], [34], [35] and [36], batch-method [36], Dreyfuss-Barbier reaction [37], Jaworsky reaction [38], Grignard-type reaction [39], [40], etc. are used. 

This experiment presents a variation on the basic idea of a Grignard synthesis, but one that does not use magnesium and that can be conducted in a mixed organic-aqueous solution. The reaction presented in this experiment is a variation on the Barbier-Grignard reaction, where zinc is used as the metal. A small amount of an ether, in this case tetrahydrofuran (THE), is still required for this reaction, but the principal component of the solvent system is water. By eliminating much of the organic solvent, this method can be used to illustrate some of the principles of... 

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