Halogen-Magnesium Exchange of Alkenyl Halides

In contrast, the bromine-magnesium exchange of alkenyl bromides does not 

The exchange of 1-silyl-substituted alkenyl halides proceeds in good yields with isomerization of the double bond (Tab. 3.18). The bulky silyl groups prefer trans orientation of the alkyl group. 

In this section, the reactions of gew-dibromocyclopropanes and dibromomethylsilanes with trialkylmagnesate reagents are described. Preparation of a chiral secondary Grignard reagent by alkylation of the chiral magnesium carbenoid species is also discussed. 

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