33770-82-0Relevant academic research and scientific papers
Cobalt-Catalyzed Kumada Coupling Forming Sterically Encumbered C-C Bonds
Brennan, Marshall R.,Darrow, William T.,Fout, Alison R.,Killion, Jack A.,Leahy, Clare A.
, (2021/12/02)
A Co(acac)3/PN precatalyst was developed and optimized for catalytic Kumada coupling of aryl Grignard reagents to sterically encumbered alkyl halides. The substrate scope demonstrates excellent yields for primary alkyl chlorides and bromides, including good performance using neopentyl chloride and neophyl chloride. Secondary alkyl halides were also successfully arylated in good yields, and the presence of β-hydrogen atoms in a substrate did not inhibit product formation. An intermolecular functional group tolerance screen was conducted which indicates that ester and amide functionality are well tolerated by the reaction conditions. Electrophiles containing ester, pyridine, and nitrile functionality were all coupled with 2-mesitylmagnesium bromide in good yields, supporting tolerance screen results. The intermolecular screen also showed that functional groups which are typically reactive with Grignard reagents such as alcohols and terminal alkynes were not well-tolerated by the reaction.
A practical procedure for iron-catalyzed cross-coupling reactions of sterically hindered aryl-grignard reagents with primary alkyl halides
Sun, Chang-Liang,Krause, Helga,Fuerstner, Alois
supporting information, p. 1281 - 1291 (2014/05/06)
Although iron-catalyzed cross-coupling reactions of arylmagnesium halides with alkyl halides are well established and proceed effectively under a variety of experimental conditions, they often find limitations when working with sterically hindered aryl-Grignard reagents. Outlined in this paper is a practical solution that allows this gap in coverage to be filled. Specifically, it is shown that bis(diethylphosphino)ethane (depe) crafts an effective coordination environment about Fe(+2). This commercially available ligand is slim enough not to interfere with the loading of the iron center even by ortho,ortho-disubstituted arylmagnesium halides, yet capable of preventing premature reductive coupling of the resulting organoiron species, which seem to be hardly basic either. The reaction is compatible with various polar functional groups as well as with substrates containing β-heteroatom substituents. Moreover, the procedure even allows encumbered neopentylic electrophiles to be arylated with donors as bulky as mesitylmagnesium bromide, whereas secondary alkyl halides tend to eliminate.
Thermolabile Hydrocarbons, XVIII. 1-Substituted Neopentyl radicals and their Dimers
Eichin, Karl-Heinz,Beckhaus, Hans-Dieter,Hellmann, Siegried,Fritz, Hans,Peters, Eva-Maria,et al.
, p. 1787 - 1821 (2007/10/02)
Five 3,4-diaryl-2,2,5,5-tetramethylhexanes 1a - e were prepared as pure meso- and DL-isomers.According to the NMR spectra, x-ray analyses for meso- and DL-1e (with an (FB)2E conformation as energy minimum for DL-1e), and force field calculations the diastereomers have distinctly different minimum energy conformations, rotational potentials, and strain enthalpies.Also the activation parameters for the thermal dissociation into 1-arylneopentyl radicals 2 are typically differing.From an entropy discussion it is concluded that sandwich-like diastereomeric radical complexes are formed in these reactions as first intermediates.Their tightness influences ΔS%.The recombinations of the radicals 2 likewise take place stereoselectively.Their substituent effects on the selectivity can also be understood by primary formation of diastereomeric complexes of radical pairs.
