Activated alkyl- and allyl-alkali metal reagents: Contrasting behaviour towards ethylene

Article abstract of DOI:10.1016/0022-328X(93)83106-6

Ethylene, hex-1-ene and (+)-α-pinene were readily metallated in methylcyclohexane with the system ⁿBuLi/LiK(OCH2CH2NMe2)2.The regioselectivity of the reaction of metallated hex-1-ene and (+)-α-pinene with CO2 could be substantially modified by the addition of Mg(OCH2CH2OEt)2.Addition of the latter also solubilizes the organometallic reagents.The allylmetallic products from the metallation of hex-1-ene and α-pinene added to ethylene under mild conditions.Whereas up to four molecules of ethylene added to metallated hex-1-ene, only one or two, depending on the reaction ratios, added to metallated α-pinene.Similar reactions involving use of a variety of other strong bases such as ⁿBuLi/^tC5H11OK and ⁿBuM (M = Li, Na, K), with and without added TMEDA, indicated that the presence of a tertiary amine, apart from assisting the metallation reaction, is essential for the occurrence of the addition.