Controlled Rearrangement of 2,3-Dilithio-1,3-butadienes to 2,5-Dilithio-1,3-butadienes: Synthesis of 2-Isopropylidene-2,5-dihydrosilols

Abstract

3,4‐Dilithio‐2,5‐dimethyl‐2,4‐hexadiene (4a) rearranges to the cross‐conjugated 2,5‐dimethylhexadienediyl dianion 11a. A mechanistic investigation proves the intermolecularity of this rearrangement, which is also observed when starting from 4b. The 3‐lithio‐2,5‐dimethylhexadienyl anion 10a with one vinyllithium and one allyllithium group, is a true intermediate in this rearrangement, its synthetic potential is employed in the reaction with dichlorosilanes to form 2‐isopropylidene‐2,5‐dihydrosilols 8.

Non-Deprotonating Methodologies for Organolithium Reagents Starting from Non-Halogenated Materials. Part 2: Transmetallation and Addition to Multiple Bonds

“…Maercker and co-workers described the preparation of the 3,4-dilithio-2,5-dimethylhexa-2,4-diene 240 by reduction of the 2,5-dimethylhexa-2,3,4-triene 239 with lithium metal, and the subsequent reaction with different electrophiles [149]. Under some reaction conditions, the intermediate 240 rearranged to the conjugated dianion 241 (Scheme 63) [150]. Different vinylsilanes [151] and the tetrakis(trimethylsilyl)butatriene [152] were also reacted with lithium producing the corresponding dianions.…”

Organodilithium Intermediates as Useful Dianionic Synthons: Recent Advances

“…Recently, Sekiguchi and co-workers isolated and characterized monomeric and dimeric structures of tetrakis(trimethylsilyl)butatriene dilithium dianion with a lithium doubly gridged bisallylic structure [115]. Dianionic compound 250 is not stable for prolonged periods of time at room temperature and rearranges to the cross-conjugated 2,5-dimethylhexadienediyl dianion 254, dianion 253 being a true intermediate in this rearrangement since the 2-isopropylidene-2,5-dihydrosilol derivative 255 is formed in the reaction with dichlorodimethylsilane (Scheme 55) [116]. The reaction of compound 250 with various mono-and bifunctionalized carbon-centered electrophiles has been investigated with special emphasis on carbonyl and carbonic acid derivatives.…”