The conceptual merger of relay catalysis with dynamic kinetic resolution strategy is reported to enable regio‐ and enantioselective C(sp3)−H bond arylation of aliphatic alcohols, forming enantioenriched β‐aryl alcohols typically with >90:10 enantiomeric ratios (up to 98:2 er) and 36‐74% yields. The starting materials bearing neighbouring stereogenic centres can be converted to either diastereomer of the β‐aryl alcohol products, with >85:15 diastereomeric ratios determined by the catalysts. The reactions occur under mild conditions, ensuring broad compatibility, and involve readily available aryl bromides, an inorganic base, and commercial Ru‐ and Pd‐complexes. Mechanistic experiments support the envisioned mechanism of the transformation occurring through a network of regio‐ and stereoselective processes operated by a coherent Ru/Pd‐dual catalytic system.
Isomerization of Terminal Epoxides by a [Pd–H] Catalyst: A Combined Experimental and Theoretical Mechanistic Study
作者:Devendra J. Vyas、Evgeny Larionov、Céline Besnard、Laure Guénée、Clément Mazet
DOI:10.1021/ja400325w
日期:2013.4.24
An unusual palladium hydride complex has been shown to be a competent catalyst in the isomerization of a variety of terminal and internal epoxides. The reaction displayed broad scope and synthetic utility. Experimental and theoretical evidence are provided for an unprecedented hydride mechanism characterized by two distinct enantio-determining steps. These results hold promise for the development of an enantioselective variant of the reaction.