Formation of organoalkali and Grignard reagents

Organometallic reagents can be prepared in cleaning baths without previous metal activation. 54 The induction period is suppressed or at least considerably shortened. Organolithiums are obtained in good yields (61-95%) from primary alkyl bromides. Secondary and tertiary alkyl bromides require longer reaction times ( 1 h). The composition of the metal is important. Lithium is frequently used as 99% pure wire. In some cases, even under sonication, it remains inert and the Li-Na mixture must be used. Ethyl-, 6 isopropenyl-, and cyclopentyl-lithium, 58 prepared by the sonochemical method, were used in s)mthesis. 

155 Small amoimts (up to 2%) of sodium in lithium dramatically improve the reactivity (Beel, J.A. Koch, W.G. Tomasi, G.E. Hermansen, D.E. Fleetwood, P.J. /. Org. Chem. 1959,24, 2036-2038). Since the Li-Na alloy does not exist (Henry, W.G. Proc. Phys. Soc. (London) 1951, B64, 195-206), lithium and sodium being immiscible below 90°C, the origins of the enhanced reactivity of the alloy remain to be explained. 

Addition to carbonyl compounds yields branched high-molecular-weight alcohols. Functional reagents, inaccessible by conventional methods, can be prepared smoothly (Fig. 29). The Grignard reagent of 4-bromo-butan-2-one dioxolane thus prepared condenses with a decalone in 82% overall yield.  

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