Ethylmagnesium bromide, reaction

The reaction of 4-bromo- or 4-iodo-isoxazoles with ethylmagnesium bromide gave the... 

In addition, there is a cleavage reaction whereby a perfluoroorgamc group is cleaved from a metal by a base, for example, phenyllithium [4], ethylmagnesium bromide [5], or a fluoride ion [6] (equations 3-5)... 

Another similar example is shown by the reaction between ris(pentafluo-rophenyI)tin bromide and ethylmagnesium bromide (equation 8)... 

This section will focus primarily on a comparison of these ring systems with their heavier chalcogen analogues. The first selenium derivative benzo-l,2,5-selenadiazole was prepared more than 115 years ago by the condensation reaction of selenium dioxide with 1,2-diaminobenzene (Eq. 11.12) and other benzo derivatives may be prepared in a similar manner. The parent 1,2,5-selenadiazole has also been reported. This reagent has been employed to make the tellurium analogue via treatment with ethylmagnesium bromide followed by the addition of tellurium tetrachloride (Eq. 11.13). ... 

Of the several syntheses available for the phenothiazine ring system, perhaps the simplest is the sulfuration reaction. This consists of treating the corresponding diphenylamine with a mixture of sulfur and iodine to afford directly the desired heterocycle. Since the proton on the nitrogen of the resultant molecule is but weakly acidic, strong bases are required to form the corresponding anion in order to carry out subsequent alkylation reactions. In practice such diverse bases as ethylmagnesium bromide, sodium amide, and sodium hydride have all been used. Alkylation with (chloroethyl)diethylamine affords diethazine (1), a compound that exhibits both antihista-minic and antiParkinsonian activity. Substitution of w-(2-chloroethyl)pyrrolidine in this sequence leads to pyrathiazine (2), an antihistamine of moderate potency. 

Name and assign R or S stereochemistry to the product(s) you would obtain by reaction of the following substance with ethylmagnesium bromide. Is the product chiral Is it optically active Explain. 

Large volumes of gas are generated, primarily ethane and ethylene, from the disproportionation of the ethyl radicals produced in the reaction of ethylmagnesium bromide with ferric chloride. The reaction should be carried out in an efficient hood, or else a tube should be run from the top of the reflux condenser to a hood. 

Ethyl 2,4-diphenylbutanoate, 47, 72 Ethyl 2,3-diphenylpropionate, 47, 74 Ethyl isocyanide, 46, 76, 77 Ethylmagnesium bromide, use with ferric chloride in cyclization of di-chloroacetone -tolylmagnesium bromide adduct to l-/>-tolylcy-clopropanol, 47,108 Ethyl nit ropheny lace late, reaction... 

The stereochemical course of the reaction may be explained by assuming a fivc-membered chelate with the nucleophile attacking the less hindered side of the C—N double bond (alkoxy-mediated S -attack)18. This model is supported by the fact that (he stereoselectivity of the reaction clearly diminishes if smaller nucleophiles, e.g., ethylmagnesium bromide, are employed. The use of valinol methyl ether effects slightly better results19. 

---