β-Carbon elimination

Though less common and less understood than β-hydride elimination, it is an important step involved in some olefin polymerization processes and transition-metal-catalyzed organic reactions.

Their calculations predict that a more electrophilic metal ion enhances the −CH3 π-donation, which consequently increases the stability of M−CH3 over M−H species.

However, to achieve the prerequisite geometry for β-H elimination (B), the adjacent methyl group experiences a significant steric repulsion from the Cp* ligand, thereby elevating the barrier to hydride transfer.

By contrast, transition state A for β-Me elimination experiences less steric interaction with the Cp* ligand.

[14] One of the examples is β-alkyl elimination of tert-alcoholates which can generate from either addition of an organometallic reagent or ligand exchange.

In addition to ring strain, aromaticity-driven β-Me elimination can be effectively employed to dealkylate steroid derivatives and some other cyclohexyl compounds.

[23] A very recent example of catalytic β-aryl elimination which leads to enantioselective synthesis of biaryl atropisomers is driven by release of distorted ring string.