Compound alkylmagnesium

Grignard reagents that contain a /3-hydrogen—e.g. 15—can reduce a carbonyl substrate by transfer of that hydrogen as a side-reaction. The so-called Grignard reduction is likely to proceed via a six-membered cyclic transition state 16 the alkyl group of alkylmagnesium compound 15 is thereby converted into an alkene 17. 

Metallation of alkynylcyclopropanes at the acetylenic end is accomplished either by deprotonation or via metal-halide exchange reaction with strong bases. Metallation of ethynylcyclopropane may be affected by KOH in DMF, ethereal EtMgBr or preferably BuLi in THF (equation 151)231. All three metal acetyl ides react with methyl ketones to give the corresponding alcohols. However, the instability of cyclopropyl ketones towards bases, especially at the reaction conditions required by KOH (20 °C, 6h), and the sensitivity of cyclopropenyl double bonds in cyclopropenyl ketone derivatives towards addition reactions of alkylmagnesium compounds, make the alkyllithium (-78 °C, instant reaction) superior to the other reagents. 

Iron(m) salts are effective catalysts for sp -sp2 coupling, which catalyze the reaction of alkylmagnesium compounds with aryl chlorides, triflates and tosylates as well as hetaryl chlorides in THF-NMP at 0°C (Scheme 49, 50).139 139a-i39d... 

Whereas the reactions of aromatic and unsaturated organomagnesium compounds with thiocarbonyl compounds are analogous to their reactions with carbonyl compounds (see Chapter 7), saturated alkylmagnesium compounds (apart from methyl) tend to react by thiophilic addition [1] ... 

Studies with symmetric alkylmagnesium compounds indicate that nucleophilic attack occurs on the least-substituted carbon atom of the oxirane (Eqs. 240 and 241). 

Solvent effects were studied in the fate 1950s for reactions of alkylmagnesium compounds with 1-hexyne in diethyl ether. These reactions have already been discussed several times in this and in Chapter 11 (see Scheme 10) [22a], When 1.0 molEq triethylamine was added to the reaction mixture, the relative reactivity of methylmagnesium iodide toward 1-hexyne, which is 7 (the reactivity of ethylmagnesium bromide was arbitrarily set... 

The sec- and terf-alkylmagnesium compounds are reported to add to terminal olefins under vigorous conditions [12,13]. Allylic Grignard reagents react reversibly, probably through a cyclic transition state [14,15]. 

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