SUPER BASES DERIVED FROM 5-HEXENYLLITHIUM AND ALKALI-METAL ALKOXIDES - REARRANGEMENTS OF 5-HEXENYLALKALIS

Solutions of 5-hexenylsodium, 5-hexenylpotassium, 5-hexenylrubidium, and 5-hexenylcesium were prepared in THF at -78 degrees C by addition of an excess (10-20 equiv) of the appropriate 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 degrees 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 l-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.