POLYLITHIUMORGANIC COMPOUNDS, 25 - CONTROLLED REARRANGEMENT OF 2,3-DILITHIO-1,3-BUTADIENES TO 2,5-DILITHIO-1,3-BUTADIENES - SYNTHESIS OF 2-ISOPROPYLIDENE-2,5-DIHYDROSILOLS

3,4-Dilithio-2,5-dimethyl-2,4-hexadiene (4a) rearranges to the cross-c onjugated 2,5-dimethylhexadienediyl dianion 11a. A mechanistic investi gation proves the intermolecularity of this rearrangement, which is al so observed when starting from 4b. The 3-lithio-2,5-dimethylhexadienyl anion Ipa with one vinyllithium and one allyllithium group, is a true intermediate in this rearrangement, its synthetic potential is employ ed in the reaction with dichlorosilanes to form 2-isopropylidene-2,5-d ihydrosilols 8.