Nagoya University develops iron photocatalyst that minimizes use of expensive chiral ligands for environmentally conscious synthesis

The development of processes that convert light energy into chemical energy has been attracting attention as an important research topic that will lead to the effective utilization of renewable solar energy.

A research group led by Professor Kazuaki Ishihara, Assistant Professor Shuhei Ohmura, and Doctoral Student Hayato Akao from the Graduate School of Engineering at Nagoya University has succeeded in developing an iron(III) photocatalyst with an ideal design that can minimize the use of expensive chiral ligand X*. Furthermore, the researchers succeeded in synthesizing bioactive natural products by utilizing selective reactions with their developed catalyst. Their results were published in the Journal of the American Chemical Society.

In 2023, the research group was the first in the world to develop stereoselective reactions using the iron(III) photocatalyst FeX*. However, to achieve the desired reaction, it was necessary to use three times the molar amount of the expensive chiral ligand X* relative to iron(III).

This time, by developing the new catalyst FeX*Y, which combines X* with an inexpensive achiral bidentate ligand Y, they succeeded in reducing the amount of X* used to one-third of that in the previous study.

The key to their success was the fact that using the catalyst FeX*Y and reacting it with substrate S under light irradiation makes it possible to selectively generate active intermediates and iron(II) salt FeY. This enabled them to proceed with the reaction stereoselectively while minimizing the use of X*. By examining the structure of Y, the researchers succeeded in developing a catalyst with performance superior to previous studies in terms of catalytic activity.

Furthermore, by utilizing selective six-membered ring formation reactions as key reactions with the developed catalyst, they achieved the world's first asymmetric total synthesis of Heitziamide A, which is expected to be applied as a respiratory burst inhibitor.

The realization of this ideal catalyst design represents an achievement that could lead to drug development that takes environmental and cost considerations into account.

Journal Information
Publication: Journal of the American Chemical Society
Title: Highly Enantioselective Radical Cation [2 + 2] and [4 + 2] Cycloadditions by Chiral Iron(III) Photoredox Catalysis
DOI: 10.1021/jacs.3c04010