"Super bases" derived from 5-hexenyllithium and alkali metal alkoxides: Rearrangements of 5-hexenylalkalis

Article abstract of DOI:10.1021/ja00094a012

Solutions of 5-hexenylsodium, 5-hexenylpotassium, 5-hexenylrubidium, and 5-hexenylcesium were prepared in THF at -78 °C by addition of an excess (10-20 equiv) of the approrpriate alkali metal alkoxide of 3-ethyl-3-heptanol to a solution of 5-hexenyllithium that had been generated from 6-iodo-1-hexene by lithium-iodine exchange. When allowed to stand at -52 °C for 1 h, the Na, K, Rb, and Cs 5-hexenylalkalis undergo prototropic rearrangement to give variable amounts of the isomeric 1-propylallyl species. Quench of such reaction mixtures afforded 1-hexene and (Z)-2-hexene as the major products along with smaller amounts of (E)-2-hexene; only traces of methylcyclopentane were detected. Under identical conditions, rearrangement of 5-hexenyllithium in the presence of an excess of lithium 3-ethyl-3-heptoxide affords only (cyclopentylmethyl)lithium.