Issue 38, 2021

Are bis(pyridine)iodine(i) complexes applicable for asymmetric halogenation?

Abstract

Enantiopure halogenated molecules are of tremendous importance as synthetic intermediates in the construction of pharmaceuticals, fragrances, flavours, natural products, pesticides, and functional materials. Enantioselective halofunctionalizations remain poorly understood and generally applicable procedures are lacking. The applicability of chiral trans-chelating bis(pyridine)iodine(I) complexes in the development of substrate independent, catalytic enantioselective halofunctionalization has been explored herein. Six novel chiral bidentate pyridine donor ligands have been designed, routes for their synthesis developed and their [N–I–N]+-type halogen bond complexes studied by 15N NMR and DFT. The chiral complexes encompassing a halogen bond stabilized iodenium ion are shown to be capable of efficient iodenium transfer to alkenes; however, without enantioselectivity. The lack of stereoselectivity is shown to originate from the availability of multiple ligand conformations of comparable energies and an insufficient steric influence by the chiral ligand. Substrate preorganization by the chiral catalyst appears a necessity for enantioselective halofunctionalization.

Graphical abstract: Are bis(pyridine)iodine(i) complexes applicable for asymmetric halogenation?

Supplementary files

Article information

Article type
Paper
Submitted
04 aug 2021
Accepted
09 sep 2021
First published
09 sep 2021
This article is Open Access
Creative Commons BY license

Org. Biomol. Chem., 2021,19, 8307-8323

Are bis(pyridine)iodine(I) complexes applicable for asymmetric halogenation?

D. von der Heiden, F. B. Németh, M. Andreasson, D. Sethio, I. Pápai and M. Erdelyi, Org. Biomol. Chem., 2021, 19, 8307 DOI: 10.1039/D1OB01532J

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