Stereoselective Synthesis of Multisubstituted Alkenes via Conformationally Labile Alkenyllithium Species

Abstract

Stereoselective synthesis of tri- and tetrasubstituted alkenylsilanes has been realized by the selective intramolecular silicon migration in the rapidly equilibrating alkenyllithium species. Subsequent copper- and palladium-mediated coupling with allyl and aryl halides provides tri- and tetrasubstituted alkenes possessing all different carbon-substituents with complete stereoselectivity. [structure: see text]

Precision Polymer Synthesis by Degenerative Transfer Controlled/Living Radical Polymerization Using Organotellurium, Organostibine, and Organobismuthine Chain-Transfer Agents

“…Organotellurium compounds are excellent precursors for carbon-centered radicals, carbanions, and carbocations. ,, The treatment of PSt 16 prepared by using TERP of ethyl 2-[(tributylsnanyl)methyl]acrylate in the presence of AIBN in trifluoromethylbenzene as a solvent produced enoate-functionalized polymer 18 via polymer-end radical 17 (Scheme a). , Tellurium−lithium transmetalation , was achieved by the treatment of 16 with butyllithium to give benzyllithium 19 , which was trapped with an electrophile, such as carbon dioxide, giving carboxylic acid 17 after treatment with acid (Scheme b) . The carboxylic acid could be further transformed to different functional groups by using standard techniques, such as esterification.…”

IntramolecularAnti‐Carbolithiation of Alkynes: Stereo‐Directing Effect of Lithium‐Coordinating Substituents

“…Addition of the aryllithium to the triple bond proceeds mostly in a syn ‐manner, leading to the alkenyllithium 32 . At elevated temperatures and/or prolonged reaction times, isomerization of the first‐formed alkenyllithium 32 to 33 occurs [74] . As a small portion of 33 is detected even at −78 °C (Table 4, entries 1 and 2), a limited anti ‐carbolithiation can also not be ruled out.…”

“…At elevated temperatures and/or prolonged reaction times, isomerization of the first-formed alkenyllithium 32 to 33 occurs. [74] As a small portion of 33 is detected even at À 78 °C (Table 4, entries 1 and 2), a limited anti-carbolithiation can also not be ruled out. From this mixture of stereoisomeric alkenyllithiums, 33 solely undergoes an O!C silyl migration by attack on the TMS/TBDMS group, shifting it to the vinylic position.…”

Brønsted Base-Catalyzed Transformation of α,β-Epoxyketones Utilizing [1,2]-Phospha-Brook Rearrangement for the Synthesis of Allylic Alcohols Having a Tetrasubstituted Alkene Moiety

“…However, the accessible allylic alcohols are still limited even with this approach. Therefore, the development of conceptually new approaches characterized by an operationally simple protocol that uses readily available starting compounds is highly anticipated to expand the scope of accessible allylic alcohols …”