Olefinic aryllithiums

It should also be noted that the 5-exo-trig cyclization of achiral olefinic organolithiums has been found to proceed enantioselectively when conducted in the presence of a chiral ligand that serves to render the lithium atom stereogenic. Thus, for example, R) 1 -allyl-3-methylindolinc has been prepared in 86 % ee by cyclization of an achiral aryllithium in the presence of an equivalent of (-)-sparteine.15... 

Lactone 7 (derived from D-isoascorbic acid) reacted readily with the aryllithium formed from bromide 8 to produce lactol 9 (Scheme 16.3). The latter underwent a facile ring-opening and Wittig olefination with methylenetriphenylphosphorane to give 6 in excellent overall yield. After 0-trifLation, a two-carbon chain extension was performed on 10 with the azaenolate derived from A-cyclohexylacetaldimine 11 and lithium diisopropylamine (LDA). After acid hydrolysis of the product imine, aldehyde 12 was isolated in 83% yield for the two steps. The (2-azaallyl)stannane 5 was prepared from aldehyde 12 in quantitative yield by treatment with (aminomethyl)tri-n-butylstannane. 

B. Cyclization Reaction of Heteroatom-substituted Olefinic Vinyllithiums and Aryllithiums... 

Grignard substitution on allylbromide gave allyl derivative 3 while chlorodimethylvinylsilane and methylacetate gave olefin intermediates 1-2 via substitution with the aryllithium derivative. Formation of bis-TFVE olefin 2 is illustrative of the pronounced reactivity of TFVE-Li toward organic electrophiles. Addition of methyl acetate to a solution of TFVE-Li, followed by protonation, yields the tertiary alcohol [p-F2C=CFOC6H4]2C(CH3)OH, which undergoes rapid dehydration to afford the bis-TFVE olefin 2. Isolated yields of 1-3 after short path... 

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