Alcohol Grignard synthesis

Tertiary alcohols can be prepared by a variation of the Grignard synthesis that uses esters as the source of the carbonyl group Methyl and ethyl esters are readily available and are the types most often used Two moles of a Grignard reagent are required per mole of ester the first mole reacts with the ester converting it to a ketone... 

Hydroxypyrroles. Pyrroles with nitrogen-substituted side chains containing hydroxyl groups are best prepared by the Paal-Knorr cyclization. Pyrroles with hydroxyl groups on carbon side chains can be made by reduction of the appropriate carbonyl compound with hydrides, by Grignard synthesis, or by iasertion of ethylene oxide or formaldehyde. For example, pyrrole plus formaldehyde gives 2-hydroxymethylpyrrole [27472-36-2] (24). The hydroxymethylpyrroles do not act as normal primary alcohols because of resonance stabilization of carbonium ions formed by loss of water. 

All that has been said in this section applies with equal force to the use of organo-lithium reagents in the synthesis of alcohols. Grignard reagents are one source of nucleophilic carbon organolithium reagents are another. Both have substantial carbanionic char acter in their- car bon-metal bonds and undergo the same kind of reaction with aldehydes and ketones. 

In a nucleophilic attack mechanism similar to Grignard synthesis of an alcohol hydrides (H") will react with carbonyls to form alcohols. Unlike Grignard synthesis of... 

Answer Mindful that we must place the CHj group on the ring, a Grignard synthesis comes to mind. Thus the dehy dration of alcohol D via procedure 11-2 is flic method or choice. 

The boronic esters (Chart 9) are easily hydrolyzed to the corresponding homoallylic alcohols using triethanolamine 98). Consequently, the allylboration sequence provides a synthesically useful alternative to the familiar Grignard synthesis of homoallylic alcohols. However, the protonolysis by triethanolamine causes a problem in the isolation of homoallylic alcohol from the thick, sticky, air sensitive boron-containing mixture. Fortunately, treatment of a pentane solution of borinate esters of 9-BBN with 1-equivalent of ethanolamine results in the rapid formation of a fluffy white... 

Grignard Synthesis.— The most important method for synthesizing aromatic alcohols is by the Grignard reaction, with magnesium alkyl or aryl halides (p. 77). The one given as an example of a tertiary aromatic alcohol may be prepared by the action of magnesium phenyl bromide, CeHs—Mg—Br, upon acetone. 

By the Grignard synthesis ketones thus always yield tertiary alcohols. Aldehydes similarly always yield secondary alcohols. 

By far the most important method of preparing alcohols is the Grignard synthesis. This is an example of the second approach, since it leads to the formation of carbon-carbon bonds. In the laboratory a chemist is chiefly concerned with preparing the more complicated alcohols that he cannot buy these are prepared by the Grignard synthesis from rather simple starting materials. The alkyl halides from which the Grignard reagents are made, as well as the aldehydes and ketones themselves, are most conveniently prepared from alcohols thus the method ultimately involves the synthesis of alcohols from less complicated alcohols. 

The class of alcohol that is obtained from a Grignard synthesis depends upon the type of carbonyl compound used formaldehyde, HCHO, yields primary alcohols other aldehydes, RCHO, yield secondary alcohols and ketones, R2CO, yield tertiary alcohols. 

Preparation of Monomers. Methyl vinyl ketone (MVK) was obtained from Pfizer Chemical Division, New York, and distilled to remove the inhibitor. Methyl isopropenyl ketone (MIPK) was prepared by the aldol condensation of methyl ethyl ketone and formaldehyde, according to the method of Landau and Irany 0. The major impurity in this monomer is ethyl vinyl ketone (5. The monomer was redistilled before use. 3 Ethyl 3 buten 2 one (EB) was prepared by the aldol condensation of methyl propyl ketone and formaldehyde. Ethyl vinyl ketone (EVK) was prepared by a Grignard synthesis of the alcohol, followed by oxidation to the ketone. t-Butyl vinyl ketone (tBVK) was prepared from pinacolone and formaldehyde by the method of Cologne (9). Phenyl vinyl ketone (PVK) was prepared fay the dehydrochlorlnatlon of 0 cbloro propiophenone (Eastman Kodak). Phenyl isopropenyl ketone (PPK) was prepared by the Mannich reaction using propiophenone, formaldehyde and dimethylamine HCl. 

Carbanion additions occur frequently at carbonyl or nitrile groups and occasionally at carbon-carbon double bonds. The Grignard synthesis of alcohols is an example ... 

Grignard synthesis. Use of the reagent for the Grignard synthesis of a secondary alcohol is illustrated by the procedure formulated ... 

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