Alkynylmagnesium bromide

With higher homologs e.g., propynyl, butynyl), 3j5-hydroxyandrost-5-en-17-one does not react well with the alkyne and potassium r-butoxide, or with the lithium alkyne in tetrahydrofuran. However, satisfactory results are obtained by use of the alkynylmagnesium bromide in tetrahydrofuran, ... 

Interaction of pyrroline-iV-oxides (373) with alkynylmagnesium bromide gives alkyne substituted nitroxyl radicals (374), (376), and (377) (Scheme 2.164) (620). 

Alkenyl p-tolyl sulfoxides.1 Various 1-alkynylmagnesium bromides react stereospecifically (with inversion) with 1 in ether/toluene to give chiral 1-alkynyl sulfoxides 2. Reduction of 2 with LiAlH4 (THF, - 90°) affords optically pure (E)-1-alkenyl p-tolyl sulfoxides (3). The corresponding (Z)-isomers are obtained by hydrogenation of 2 with the Wilkinson catalyst. 

The reactions of propargyl bromide or propargyl tosylate with alkynylmagnesium bromide gives small amounts of 1,3-substitution products, allenynes, RC=C-CH=C=C. These can be removed however, by heating the product mixture. During this treatment, the allenynes... 

Alkynylmagnesium bromides (general procedure for metallation of 1-alkynes by ethylmagnesium bromide) [6]... 

Reactions with three moles of organolithium reagent or allyl and alkynylmagnesium bromide leads to the tetrasubstituted product (equation 14). 

The formadon of alkynenitriles from alkynylmagnesium halides and cyanogen chloride was described far die fust tune by Grignard [114], A number of these nitriles have been prepared in our laboratory from alkynyllithium and cyanogen chloride using I O as a solvent [115], Cyanogen bromide is unsuitable because the alkynylide attacks on bromine [2],... 

The use of cobalt species to catalyze cross-coupling reactions of activated or unactivated alkyl halides with alkynyl Grignard reagents in order to form C(sp)-G(sp ) bonds is also of interest. Cobalt compleres promote the crossbenzyl chlorides and bromides react with 2-trimethylsilylethynyl- and 1-octyn-l-ylmagnesium halides to provide l-aryl-2-alkynes in the presence of a catalytic amount of a cobalt complex [100,101]. 

As shown in Table 1, a wide variety of metal countercations have been shown to participate in this reaction. Under the same reaction conditions, alkynylmetals containing Zn exhibit the highest reactivity (Entfy 6), which is followed by those of Mg (Entries 4 and 5), Al (Entries 12-14), and Sn (Entries 16 and 17). Although the product yield observed with 1-heptynytmagnesium bromide was modest (49%), alkynylmagnesium reagents have since been shown to be very satisfactory in many cases. ... 

---