Introducing Type Ⅲ Metal Complex-Stabilized Olefin Radical Cation Induced Addition: A New Mechanism for Palladium-Catalyzed Wacker-Type Oxidation of Terminal Alkenes

05 March 2024, Version 1
This content is a preprint and has not undergone peer review at the time of posting.


To expand the substrate scope of the recently named “Radical Cation Induced Addition (RCIA)”, allowing functionalization of inactivated alkenes, the concept of “metal complex-stabilized olefin RCIA” as a type III RCIA is introduced here, with a rational design on the delocalization of radical spin the via metal-olefin interaction and through space interaction with other ligands. The feasibility of Pd-olefin radical cation complex via one-electron oxidation enabled by an oxidant is demonstrated in the Pd-catalyzed Wacker-type oxidation of terminal alkenes. The new mechanisms involved with “Pd(II) to Pd(I) catalytic cycle” matches the reported kinetic data of both the Wacker process and the Tsuji-Wacker oxidation of olefins to ketones and/or aldehydes, and it could explain the long-time unexplained phenomenon of a water nucleophilic attack onto a negatively charged π-olefin coordinated with Pd atom. Furthermore, with the new mechanisms, the stereochemistry of the debated syn/anti attack and the regioselective control in Tsuji-Wacker oxidation for either ketones or aldehydes would also be well explainable. A new concept of “on Pd through space interactions” is too proposed to explain the root of the anti-Markovnikov selectivity by the resulted “through space conjugation”. Implications in the rational design of recyclable Pd precatalysts with a water-soluble ligand for aldehyde selective Tsuji-Wacker oxidation of olefins with the concept of “in-situ surfactant”, and implications for the rational design of domino/one-pot reactions toward sustainable complex molecules with functionalities starting from olefins, by merging with organocatalysis, are also included.


Wacker oxidation mechanism
single electron transfer
on Pd through space interactions
2-hydride transfer
water addition


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