3-Neopentylallyllithium II. Reactions in hydrocarbon media

Product distributions are reported for several reactions in hydrocarbon solvent of 3-neopentylallyllithium, the 1,4-addition product of tert-butyllithium and 1,3-butadiene. Protolysis with several agents yields predominately the “normal” products (Ia) and (Ib)] with less than 6% of the terminal olefin observed. The ratio of the cis/trans isomers (Ia) and (Ib)] parallels the ratio of the lithiated forms before protolysis. Reaction with chlorotrimethylsilane also shows no “rearranged” product. Carboxylation and ketone addition reactions, however, proceed with marked rearrangement unless the ketone is very hindered. Di-tert-butyl ketone and benzophenone give no rearranged product. Addition of a second mole of butadiene also results in predominant (60%) rearrangement of the neopentylallyl group. Bromination with molecular bromine and 1,2-dibromoethane yields a mixture of dibromo-derivatives in the former case and C₁₆-diolefin coupling products in the later case. Tentative mechanisms for protolysis and addition reactions are discussed.