A widely applicable, practical, and scalable synthetic method for efficient ene‐type double oxidation of alkenes is reported via a two‐step alkenyl thianthrenium umpolung/Kornblum‐Ganem oxidation strategy. This chemo‐ and stereoselective procedure allows easy access to various α,β‐unsaturated carbonyls that may be otherwise difficult or cumbersome to synthesize by conventional methods. For α‐olefins, this metal‐free transformation can be tuned according to synthetic needs to produce either the elusive (Z)‐unsaturated aldehydes or their (E) counterparts. Moreover, this strategy has enabled streamlined synthesis of distinct butadienyl pheromones and kairomones.

A widely applicable, practical, and scalable synthetic method for efficient ene-type double oxidation of alkenes is reported via a two-step alkenyl thianthrenium umpolung/Kornblum-Ganem oxidation strategy. This chemo-and stereoselective procedure allows easy access to various α,β-unsaturated carbonyls that may be otherwise difficult or cumbersome to synthesize by conventional methods. For α-olefins, this metal-free transformation can be tuned according to synthetic needs to produce either the elusive (Z)-unsaturated aldehydes or their (E) counterparts. Moreover, this strategy has enabled streamlined synthesis of distinct butadienyl pheromones and kairomones.