Grignard syntheses

See the discussion about the properties of polymers produced from unsymmetric monomers in section 6.3. Head to head (H-H) arrangements can be produced by special techniques of polymerization (19). 

The polymers are crystalline, with a melting temperature of 187°C and a glass transition temperature of 87°C. In contrast, H-T PIB is a rubbery polymer, with a glass transition temperature of -61°C. Further, the polymer contains bromine end groups. As a side reaction, cyclization is observed. 

An alternative to produce H-H arranged PIB is the coupling via the Wurtz-Fittig reaction. This is the coupling of alkyl halides by the treatment with metallic sodium or other metals such as lithium and zinc. However, this type of reaction results in substantially branched polymers with a comparatively low molecular weight (19). 

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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. 

Although the metal-halogen exchange reaction is the preferred method of synthesis, the conventional Grignard synthesis through the reaction of a per-fluoroorgano halide and magnesium occasionally is still used [49, 50]... 

The method is an extension of the well-known Grignard synthesis in ethers to the use of nonsolvating media, and is a development of procedures previously reported.2-6 A version of it has... 

The wide range over which the Grignard synthesis can be applied should be sufficiently evident from this short review. 

Related to the Grignard synthesis is that of Reformatzky in which zinc is used to condense the esters of a-halogenated fatty acids with ketones, e.g. ... 

The Grignard is made from 4-bromoanisole, Mg (3 % excess), I2 catalyst, in tetrahydrofuran (3 M), at 70 °C. The major problem is the formation of the homo coupled product during the Grignard synthesis. Up to 6% of 4,4 -dimethoxybiphenyl may be formed. The amount depends on the type of... 

Present Day Methods. In the Grignard Synthesis (82,83), chlorobenzene [108-90-7] is converted to phenylmagnesium chloride which reacts with ethylene oxide [75-21-8] at 100°C to give (3-phenylethoxy magnesium chloride which is then decomposed with sulfuric acid to give PEA. 

Manufacture. Current commercial methods for making PEA include Grignard synthesis. Friedel-Crafts process, and catalytic hydrogenation of styrene oxide. 

Each of the following equations represents a possible but not actually feasible Grignard synthesis. Consider each equation and determine why it will not proceed satisfactorily as written. Give your reasoning and show what the actual product will be. 

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... 

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

The method is an extension of the well-known Grignard synthesis in ethers to the use of nonsolvating media, and is a development of procedures previously reported.2-6 A version of it has been employed with straight-chain primary alkyl chlorides, bromides, and iodides from C2 to Cu,5-7 and in solvents (or an excess of the halide) which permit reaction temperatures above 120°, with simple aryl halides such as chlorobenzene and 1-chloro-naphthalene. Branched-chain primary, secondary, and tertiary alkyl halides, allyl, vinyl, and benzyl halides either fail to react or give extensive side reactions. Better results are reported to be obtained in such cases with the use of catalytic quantities of a mixture of an alkoxide and an ether such as diethyl ether or tetrahydrofuran in a hydrocarbon medium, but the products are not, of course, completely unsolvated.4... 

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. 

In 1941 Gakhokidze40 realized a different type of Grignard synthesis on a carbohydrate acid derivative. Methyl L-ery(liro-3,4,5-trimethoxy-2-oxovalerate (XXXII), was treated with one mole of methylmagnesium iodide to produce methyl 2-methyl-2-hydroxy-L-er /(firo-3,4,5-trimethoxy-valerate (XXXIII). The configuration of the second carbon atom in... 

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... 

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