Issue 27, 2021

Achiral and chiral NNN-pincer nickel complexes with oxazolinyl backbones: application in transfer hydrogenation of ketones

Abstract

We describe the synthesis of new NNN-oxazolinyl-pincer nickel complexes and their application in the transfer hydrogenation of ketones. Achiral NNN-ligands, R′2-oxazolinyl-2-C6H4-NH-C(O)CH2NEt2 [(R′2-OxNNNEt2)–H; R’ = H (3a), R′ = Me (3b)], and chiral ligands, (R)-R′-oxazolinyl-2-C6H4-NH-C(O)CH2NEt2 [(R)-(R′-OxNNNEt2)–H; R′ = Ph (3c), R′ = CH2Ph (3d), R′ = iPr (3e), R′ = CH2iPr (3f)], were efficiently synthesized. Treatment of these ligands with (DME)NiCl2 afforded the desired amido-pincer nickel complexes, (R′2-OxNNNEt2)NiCl [R′ = H (4a), R′ = Me (4b)] and (R′-OxNNNEt2)NiCl [R′ = Ph (4c), R′ = CH2Ph (4d), R′ = iPr (4e), R′ = CH2iPr (4f)], in good yields. All the ligand precursors and nickel complexes were thoroughly characterized by various analytical techniques. The molecular structures of 4a, 4d and 4f were established by X-ray crystallography. The developed nickel complexes were found to be efficient catalysts for the transfer hydrogenation of ketones using iPrOH as a viable hydrogen source. Enantioselectivity in hydrogenation was not observed with the developed chiral catalysts.

Graphical abstract: Achiral and chiral NNN-pincer nickel complexes with oxazolinyl backbones: application in transfer hydrogenation of ketones

Supplementary files

Article information

Article type
Paper
Submitted
07 Apr 2021
Accepted
30 Mai 2021
First published
31 Mai 2021

New J. Chem., 2021,45, 11927-11936

Achiral and chiral NNN-pincer nickel complexes with oxazolinyl backbones: application in transfer hydrogenation of ketones

R. A. Jagtap, S. B. Ankade, R. G. Gonnade and B. Punji, New J. Chem., 2021, 45, 11927 DOI: 10.1039/D1NJ01698A

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