Compounds Grignards Synthesis

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. 

Which of the following compounds would make the best solvent in a Grignard synthesis with an alkylbromide ... 

The preferred synthesis of R4Pb and RePb2 compounds on a laboratory scale involves the reaction of a lead(II)halide with a reactive organometallic compound, such as a Grignard reagent or an organolithium compound. The synthesis is postulated to proceed stepwise, according to the equations 196> ... 

These results led Schumb and Sailer to devise a two-stage synthesis 6 which allows a much better control. The sodium first is allowed to react with a halide such as chlorobenzene in a solvent to yield phenyl sodium. After the heat of this reaction is dissipated, the phenyl sodium is mixed with the silicon halide in solution, and a milder reaction ensues. In this way hexaphenyldisilane was made from hexachlorodisilane, and hexaphenyldisiloxane from hexachlorodisiloxane. Moreover, phenyltrichlorosilane was made by the action of less than one equivalent of sodium phenyl on silicon tetrachloride. The use of a separately prepared sodium alkyl in this way provides the same degree of control as in a Grignard synthesis, and the reactions indeed are very similar. Organolithium compounds probably could be used in the same way. 

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. 

Derivation By a modified Grignard synthesis. Use Synthesis of organic compounds, phosphonium salts, other phosphorus compounds, polymerization initiator. 

We shall analyse compounds like (3) in Chapter 19. The Grignard synthesis is trivial. 

Grignard synthesis is the method that Hein [9] used first to synthesize organochromium compounds in 1919. Anhydrous chromium chloride reacts with PhMgBr in an ether solution, forming an inflammable, paramagnetic black solid. Phenyl-chromium compound is obtained by hydrolysis of the black solid. 

The Fisher-Hafner synthesis is the convenient synthetic method for various kinds of ( -(arene))2Cr type compounds, since it yields a single product different from the Grignard synthesis. However, precautions should be taken on compounds on which transalkylations or isomerization tends to proceed [16]. For example, mesitylene is reactive as described above in that a transalkylation partly proceeds to afford xylene and tetramethylbenzene. The transalkylation such as the reaction with... 

Outline how each of the following alcohols could be made from the indicated starting material and other necessary compounds using the Grignard synthesis. 

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