Recent Advances in Acid‐Mediated Ring‐Opening Reactions of Cyclopropanol Derivatives

Cyclopropanols and related cyclopropyl derivatives, featuring three‐membered ring strain, hydroxyl‐directed vicinal polarization, and distinctive σ‐bonding characteristics, serve as valuable three‐carbon synthons. Acid‐mediated ring‐opening enables controlled cleavage of otherwise highly strained C─C σ‐bonds, facilitating carbonyl construction, ring expansion, rearrangements, and complex cyclic frameworks. This review summarizes ring‐opening reactions promoted by Brønsted acids, conventional Lewis acids, π‐Lewis acids, and other acidic or acid‐like systems, with emphasis on acid type and activation mode. Brønsted acids generally induce C─C bond cleavage, nucleophilic trapping, and semipinacol‐type migration via protonation or acidic media, affording linear carbonyls, unsaturated ketones, and cyclobutanones. Conventional Lewis acids coordinate to hydroxy, acetal, carbonyl, or leaving groups, triggering cyclopropyl–allyl rearrangements, oxocarbenium‐trapping cyclizations, Prins‐type expansions, semipinacol rearrangements, and intermolecular couplings. π‐Lewis acids are particularly effective for ring expansion, cycloisomerization, and skeletal rearrangement of alkynyl‐, allenyl‐, and enynyl‐substituted cyclopropanols. Additionally, solid acids, organic acids, hydrogen‐bond donors, ion pairs, and cooperative acid‐like systems offer new opportunities for selectivity control. By comparing different acid systems, activation sites, and reaction pathways, this review aims to clarify the relationships among acid type, key intermediates, and product structures in acid‐mediated cyclopropanol ring opening.