Issue 5, 2022

Hydroboration and reductive amination of ketones and aldehydes with HBpin by a bench stable Pd(ii)-catalyst

Abstract

A palladium(II) complex [(κ4-{1,2-C6H4(N[double bond, length as m-dash]CH–C6H4O)2}Pd] (1) supported by a dianionic salen ligand [1,2-C6H4(N[double bond, length as m-dash]CH–C6H4O)2]2− (L) was synthesised and used as a molecular pre-catalyst in the hydroboration of aldehydes and ketones. The molecular structure of Pd(II) complex 1 was established by single-crystal X-ray diffraction analysis. Complex 1 was tested as a competent pre-catalyst in the hydroboration of aldehydes and ketones with pinacolborane (HBpin) to produce corresponding boronate esters in excellent yields at ambient temperature under solvent-free conditions. Further, the complex 1 proved to be a competent catalyst in the reductive amination of aldehydes with HBpin and primary amines under mild and solvent-free conditions to afford a high yield (up to 97%) of corresponding secondary amines. Both protocols provided high conversion, superior selectivity and broad substrate scope, from electron-withdrawing to electron-donating and heterocyclic substitutions. A computational study based on density functional theory (DFT) revealed a reaction mechanism for Pd-catalysed hydroboration of carbonyl species in the presence of HBpin. The protocols also uncovered the dual role of HBpin in achieving the hydroboration reaction.

Graphical abstract: Hydroboration and reductive amination of ketones and aldehydes with HBpin by a bench stable Pd(ii)-catalyst

Supplementary files

Article information

Article type
Paper
Submitted
30 Nov 2021
Accepted
07 Jan 2022
First published
07 Jan 2022

Org. Biomol. Chem., 2022,20, 1103-1111

Hydroboration and reductive amination of ketones and aldehydes with HBpin by a bench stable Pd(II)-catalyst

S. Mahato, P. Rawal, A. K. Devadkar, M. Joshi, A. Roy Choudhury, B. Biswas, P. Gupta and T. K. Panda, Org. Biomol. Chem., 2022, 20, 1103 DOI: 10.1039/D1OB02339J

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