A silylium-ion-promoted ring-opening hydrosilylation of unactivated cyclopropanes is reported. The reaction is facilitated by the γ-silicon effect, and the regioselectivity is influenced by various stabilizing effects on the carbenium-ion intermediates, including the β-silicon effect. The experimental observations are in accord with the computed reaction mechanism. The work also showcases the ability of silylium ions to isomerize cyclopropyl to allyl groups, and the resulting α-olefins engage in a silylium-ion-mediated disilylation with hexamethyldisilane.

A metal‐free, intermolecular syn‐addition of hexamethyldisilane across simple alkenes is reported. The catalytic cycle is initiated and propagated by the transfer of a methyl group from the disilane to a silylium‐ion‐like intermediate, corresponding to the (re)generation of the silylium‐ion catalyst. The key feature of the reaction sequence is the cleavage of the Si−Si bond in a 1,3‐silyl shift from silicon to carbon. A central intermediate of the catalysis was structurally characterized by X‐ray diffraction, and the computed reaction mechanism is fully consistent with the experimental findings.

The preparation of a molecule with two alkyl‐tethered silylium‐ion sites from the corresponding bis(hydrosilanes) by two‐fold hydride abstraction is reported. The length of the conformationally flexible alkyl bridge is crucial as otherwise the hydride abstraction stops at the stage of a cyclic bissilylated hydronium ion. With an ethylene tether, the open form of the hydronium‐ion intermediate is energetically accessible and engages in another hydride abstraction. The resulting bis(silylium) ion has been NMR spectroscopically and structurally characterized. Related systems based on rigid naphthalen‐n,m‐diyl platforms can only be converted into the dications when the positively charged silylium‐ion units are remote from each other (1,8 versus 1,5 and 2,6).

For a long time, the Me3Si group has been ostracized from the family of aryl‐ and heteroatom‐substituted congeners for the difficulties associated with its further chemoselective manipulation into another synthetically useful functional group. A hypervalent iodine reagent has now been shown to do exactly that by electrophilic demethylation. Coupled with the Tamao–Fleming oxidation, the Me3Si group becomes a placeholder for a hydroxy group.

A transition‐metal‐free, redox‐neutral, organocatalytic C3‐alkenylation of pyrroles is reported. Readily available aldehydes were employed as alkenylating agent and the reaction tolerates several key functional groups. The E‐alkenylated products were isolated in moderate to exclusive selectivity. A one‐pot two‐fold alkenylation strategy is also developed for further downstream modifications. To show the applicability, synthetically challenging indolylpyrrole derivatives were synthesized using Cadogan cyclization.