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Exploring Regioselective Bond Cleavage and Cross‐Coupling Reactions using a Low‐Valent Nickel Complex
Author(s) -
Desnoyer Addison N.,
Friese Florian W.,
Chiu Weiling,
Drover Marcus W.,
Patrick Brian O.,
Love Jennifer A.
Publication year - 2016
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201504959
Subject(s) - transmetalation , decarbonylation , chemistry , bond cleavage , aryl , medicinal chemistry , regioselectivity , nickel , ligand (biochemistry) , yield (engineering) , coupling reaction , catalysis , stereochemistry , organic chemistry , biochemistry , receptor , materials science , metallurgy , alkyl
Recently, esters have received much attention as transmetalation partners for cross‐coupling reactions. Herein, we report a systematic study of the reactivity of a series of esters and thioesters with [{(dtbpe)Ni} 2 (μ‐η 2 :η 2 ‐C 6 H 6 )] (dtbpe=1,2‐bis(di‐ tert ‐butyl)phosphinoethane), which is a source of (dtbpe)nickel(0). Trifluoromethylthioesters were found to form η 2 ‐carbonyl complexes. In contrast, acetylthioesters underwent rapid C acyl −S bond cleavage followed by decarbonylation to generate methylnickel complexes. This decarbonylation could be pushed backwards by the addition of CO, allowing for regeneration of the thioester. Most of the thioester complexes were found to undergo stoichiometric cross‐coupling with phenylboronic acid to yield sulfides. While ethyl trifluoroacetate was also found to form an η 2 ‐carbonyl complex, phenyl esters were found to predominantly undergo C aryl −O bond cleavage to yield arylnickel complexes. These could also undergo transmetalation to yield biaryls. Attempts to render the reactions catalytic were hindered by ligand scrambling to yield nickel bis(acetate) complexes, the formation of which was supported by independent syntheses. Finally, 2‐naphthyl acetate was also found to undergo clean C aryl −O bond cleavage, and although stoichiometric cross‐coupling with phenylboronic acid proceeded with good yield, catalytic turnover has so far proven elusive.