Grignard reagent, methylmagnesium

Fair yields of alkoxy alcohols are obtained from a-alkoxy ketones and Grignard reagents. Methylmagnesium iodide and phenoxyacetone give plienoxy-l-butyl alcohol (88%). ... 

C-sodium acetate is produced by the reaction of the Grignard reagent, methylmagnesium bromide in diethyl ether, with cyclotron-produced nC-carbon dioxide at -15°C (Oberdorfer et al, 1996). After reaction, the product is allowed to react with O-phthaloyl dichloride to produce nC-acetyl chloride, which is then hydrolyzed to 11C-acetate with saline. The solution is filtered through a 0.22-pm membrane filter. 11C-acetate has been found to be stable at pH between 4.5 and 8.5 for up to 2 h at room temperature. The overall yield is about 10-50%. It is used for the measurement of oxygen consumption (oxidative metabolism) in the heart, since acetyl CoA synthetase converts 11C-acetate to acetyl coenzyme A after myocardial uptake, which is metabolized to 11C-C02 in the tricarboxylic acid cycle. 

C-flumazenil is commonly labeled at the A7-me 1 11 yl position by N-methylation with 11 C-iodomethane, which is prepared from 11C-C02, and using the freshly prepared Grignard reagent, methylmagnesium bromide (Maziere et al, 1984). The specific activity is very important for this product and therefore is purified by HPLC to give an optimum value between 0.5 and 2Ci/Vmol (18.5-74GI k]/i imol). It remains stable for up to 3 h at room temperature at pH 7.0. The molecular structure of 11C-fumazenil is shown in Fig. 8.2b. 

Although it may be supposed from the discussion of item 4 of Table 9.9 (where an ester, reacted with a Grignard reagent [methylmagnesium bromide, CHsMgBr ], first underwent substitution and subsequently reacted further to yield a tertiary alcohol) that amides such as N,N-diethyl cyclohexanecarboxamide (item 2 in Table 9.10) might behave the same, it falls out that they do not generally do so. ... 

The Grignard reagent attacks the unsaturated ketones (3) and (6) from the relatively unhindered ot- or jS-side, respectively, perpendicular to the plane of the conjugated system. An analogous transition state (10) leading to axially substituted 1,6-addition products (11) from A -3-ketones (9) with methylmagnesium halide was suggested by Marshall. ... 

The action of Grignard reagents on 20,20-ethylenedioxy-12-ketones and 20a-hydroxy-12-ketones also shows that the attack of methylmagnesium iodide on 12-ketones proceeds mainly from the i -side of the steroid mole-cule. ... 

Nitriles (RC=N) react with Grignard reagents (R MgBr). The reaction produc from 2-methylpropanenitrile with methylmagnesium bromide has the fol lowing spectroscopic properties. Propose a structure. 

PHENYL-METHOXY)CARBONYL] -L-PROLYL]-GLYCYL]-, ETHYL ESTER [57621-06-41,56,88 Grignard reagent, 3-(dimethylamino)propyl-magnesium chloride, 55, 127 methylmagnesium bromide, 55, 63... 

A complex reaction takes place when dichlorobis(triphenylphosphine)-nickel (5) is treated with excess methylmagnesium bromide in ether. Detectable amounts of benzene, toluene, and biphenyl are formed, together with mixed phosphines. Nickel appears to be necessary for the substitution reaction since triphenylphosphine alone does not react with the Grignard reagent. 

Methylmagnesium bromide (191) exerts a great influence on the stereoselectivity of the reactions between mesitonitrile oxide 10 and the Baylis-Hillman adducts 192. In the absence of a Grignard reagent, a mixture of isomers is formed in which compounds 194 are the main products. The presence of a Grignard reagent reverses the stereoselectivity (Scheme 9.59). When Fisera [107] performed these reactions under microwave irradiation, the reaction times decreased from days to less than 5 min without any loss of stereoselectivity for noncatalyzed cycloadditions, but with a small change in the stereoselectivity in the chelated reactions. 

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