Reactions of Tertiary Aliphatic Cations with Silylated Alkynes: Substitution, Cyclization and Unexpected C‐H Activation Products

Capozzi's groundbreaking work in 1982 introduced a fascinating reaction involving highly reactive tertiary aliphatic cations and silylated alkynes. This reaction provided an innovative solution to the challenge of coupling a fully substituted tertiary aliphatic fragment with an alkyne moiety. Building upon Capozzi's pioneering efforts, we started an extensive exploration of reaction conditions to expand the initial scope of this reaction. Through meticulous control of the reaction parameters, we uncovered conditions capable of accommodating various functional groups, thereby enhancing the reaction's applicability. Intriguingly, our study revealed remarkable high diastereoselectivities for substrates with substitution in the a‑position. Additionally, we made an unexpected discovery: an intriguing C‐H activation of a cyclooctane ring furnishing a cyclooctane‐fused cyclobutene. These findings not only extend the utility of Capozzi's original concept but also underscore the potential of highly reactive cations in modern organic C‐H activation reactions.