Alkyllithiums tandem cyclization

The stereocontrol inherent in the totally regiospecific 5-exo-trig isomerizations of substituted 5-hexenyllithiums may be exploited for the stereoselective synthesis of bicyclic systems by tandem cyclization of acyclic diolefinic alkyllithiums. To date, this strategy has not been widely applied, and the first examples were reported by Bailey and Rossi who were able to cyclize the organolithiums derived from iodides 113 and 115 in the presence of TMEDA to afford the polycarbocyclic products 114 and 116 (Scheme 33)61. 

In the same context, Bailey and Ovaska have described a tandem cyclization of an enynyl alkyllithium generated by low-temperature iodine-lithium exchange on iodide 269. Two sequential 5-exo cyclization reactions when warmed to room temperature afford... 

The regiospecific 5-exo-trig cyclizations of substituted 5-hexenyllithiums was exploited for the stereoselective synthesis of bicyclic systems by tandem cyclization of acyclic diolefinic alkyllithiums [42]. However, this carbocycle synthesis has three major limitations ... 

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