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Conclusions
In summary, unactivated tertiary amides, such as N-methyl-N-
phenylbenzamide, reacted with primary amines in the pres-
ence of NiCl2 and a briphos ligand to deliver transamidated
secondary amides in good yields. The employment of NiCl2
has several advantages, as it is an inexpensive and easily
handled reagent. Among the briphos ligands, N-3,5-dimethoxy-
phenyl substituted briphos having a tert-butyl substituent at
the phenol moiety, L4, provided optimal results. It was found
that briphos ligands bearing electron-donating groups and
sterically bulky substituents exhibited superior activity com-
pared to other briphos ligands. We believe that the steric
bulkiness of the ligands plays a major role in improving the
reactivity of the Ni catalysts. Accordingly, tert-butyl substituted
briphos ligands L3, L4, and L6 showed better reactivity than
the non-substituted briphos ligands L1, L2, and L5. Among
tert-butyl substituted briphos ligands, electronic tuning was
achieved with methoxy groups, showing that L4 is the optimal
ligand. We will not discuss the detailed ligand effect further at
this moment, but will continue to investigate the reaction
mechanism to completely understand the ligand effect.
Aromatic amines, including heteroaromatic amines, benzyl
amines, and alkyl amines, afforded the transamidated pro-
ducts in moderate to good yields. Various substituted
N-methyl-N-phenylbenzamides displayed good activity in the
transamidation of aniline.
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There are no conflicts to declare.
Acknowledgements
This research was supported by
a National Research
Foundation of Korea (NRF) grant funded by the Korea govern-
ment (NRF-2012M3A7B4049655 and 2020R1A2C2013420). The
spectral data were obtained from the Gwangju Center of Korea
Basic Science Institute.
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