TY - JOUR
T1 - General copper-catalyzed coupling of alkyl-, aryl-, and alkynylaluminum reagents with organohalides
AU - Shrestha, Bijay
AU - Thapa, Surendra
AU - Gurung, Santosh K.
AU - Pike, Ryan A.S.
AU - Giri, Ramesh
N1 - Funding Information:
We thank the University of New Mexico (UNM) for financial support and upgrades to the NMR (NSF grants CHE08-40523 and CHE09-46690) and MS Facilities.
Publisher Copyright:
© 2016 American Chemical Society.
PY - 2016/2/5
Y1 - 2016/2/5
N2 - We report the first example of a very general Cu-catalyzed cross-coupling of organoaluminum reagents with organohalides. The reactions proceed for the couplings of alkyl-, aryl-, and alkynylaluminum reagents with aryl and heteroaryl halides and vinyl bromides, affording the cross-coupled products in good to excellent yields. Both primary and secondary alkylaluminum reagents can be utilized as organometallic coupling partners. These reactions are not complicated by β-hydride elimination, and as a result rearranged products are not observed with secondary alkylaluminum reagents even for couplings with heteroaryl halides under "ligand-free" conditions. Radical clock experiment with a radical probe and relative reactivity study of Ph3Al with two haloarenes, 1-bromonaphthalene and 4-chlorobenzonitrile, having two different redox potentials indicates that the reaction does not involve free aryl radicals and radical anions as intermediates. These results combined with the result of the Hammett plot obtained by reacting Ph3Al with iodoarenes containing p-H, p-Me, p-F, and p-CF3 substituents, which shows a linear curve (R2 = 0.99) with a ρ value of +1.06, suggest that the current transformation follows an oxidative addition-reductive elimination pathway.
AB - We report the first example of a very general Cu-catalyzed cross-coupling of organoaluminum reagents with organohalides. The reactions proceed for the couplings of alkyl-, aryl-, and alkynylaluminum reagents with aryl and heteroaryl halides and vinyl bromides, affording the cross-coupled products in good to excellent yields. Both primary and secondary alkylaluminum reagents can be utilized as organometallic coupling partners. These reactions are not complicated by β-hydride elimination, and as a result rearranged products are not observed with secondary alkylaluminum reagents even for couplings with heteroaryl halides under "ligand-free" conditions. Radical clock experiment with a radical probe and relative reactivity study of Ph3Al with two haloarenes, 1-bromonaphthalene and 4-chlorobenzonitrile, having two different redox potentials indicates that the reaction does not involve free aryl radicals and radical anions as intermediates. These results combined with the result of the Hammett plot obtained by reacting Ph3Al with iodoarenes containing p-H, p-Me, p-F, and p-CF3 substituents, which shows a linear curve (R2 = 0.99) with a ρ value of +1.06, suggest that the current transformation follows an oxidative addition-reductive elimination pathway.
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U2 - 10.1021/acs.joc.5b02077
DO - 10.1021/acs.joc.5b02077
M3 - Article
AN - SCOPUS:84957540449
SN - 0022-3263
VL - 81
SP - 787
EP - 802
JO - Journal of Organic Chemistry
JF - Journal of Organic Chemistry
IS - 3
ER -