Hydroboration and reductive amination of ketones and aldehydes with HBpin by a bench stable Pd(II)-catalyst.
Shreya MahatoParveen RawalDevadkar Ajitaro KisanMayank JoshiAngshuman Roy ChoudhuryBhaskar BiswasPuneet GuptaTarun K PandaPublished in: Organic & biomolecular chemistry (2022)
A palladium(II) complex [(κ 4 -{1,2-C 6 H 4 (NCH-C 6 H 4 O) 2 }Pd] (1) supported by a dianionic salen ligand [1,2-C 6 H 4 (NCH-C 6 H 4 O) 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.
Keyphrases
- room temperature
- ionic liquid
- density functional theory
- reduced graphene oxide
- highly efficient
- carbon dioxide
- metal organic framework
- molecular dynamics
- visible light
- air pollution
- gold nanoparticles
- high resolution
- magnetic resonance imaging
- electron microscopy
- computed tomography
- single molecule
- crystal structure
- mass spectrometry
- molecular dynamics simulations
- structural basis