Premium
Manganese‐Catalyzed Cross‐Coupling of Aryl Halides and Grignard Reagents by a Radical Mechanism
Author(s) -
Antonacci Giuseppe,
Ahlburg Andreas,
Fristrup Peter,
Norrby PerOla,
Madsen Robert
Publication year - 2017
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.201700981
Subject(s) - chemistry , aryl , manganese , halide , catalysis , mechanism (biology) , reagent , coupling (piping) , grignard reagent , combinatorial chemistry , photochemistry , organic chemistry , medicinal chemistry , polymer chemistry , alkyl , mechanical engineering , philosophy , epistemology , engineering
The substrate scope and the mechanism have been investigated for the MnCl 2 ‐catalyzed cross‐coupling reaction between aryl halides and Grignard reagents. The transformation proceeds rapidly and in good yield when the aryl halide component is an aryl chloride containing a cyano or an ester group in the para position or a cyano group in the ortho position. A range of other substituents gave no conversion of the aryl halide or led to the formation of side products. A broader scope was observed for the Grignard reagents, where a variety of alkyl‐ and arylmagnesium chlorides participated in the coupling. Two radical‐clock experiments were carried out, and in both cases an intermediate aryl radical was successfully trapped. The cross‐coupling reaction is therefore believed to proceed by an S RN 1 mechanism, with a triorganomanganate complex serving as the most likely nucleophile and single‐electron donor. Other mechanistic scenarios were excluded based on the substrate scope of the aryl halide.