| 研究実績の概要 |
This project aims at the creation of a ligand that can control the reactivity of organoiron species and achieve an efficient and versatile iron catalyst for organic synthesis, surpassing precious metal catalysis. We discovered that an iron/diphosphine catalyst, in the presence of a diorganozinc base and a mild dichloroalkane oxidant enables the stoichiometric cross-coupling of aromatic amides with heteroarenes. The cross-coupling of two different C-H substrates is especially difficult because of competing homocoupling, and typically a large excess of one of the coupling partners must be used; however, the iron catalyst enabled the cross-coupling with perfect selectivity, and homocoupling of the starting materials was not observed at all. The reaction could also be applied to efficient multifold C-H cross-coupling. For example, three C-H bonds in a tris-thiophene molecule could be coupled with three amide molecules’ C-H bonds to create three new C-C bonds in almost quantitative yield. Mechanistic studies suggested that directed C-H activation of the amide takes place first, then the resulting iron intermediate activates the C-H bond of the heteroarene in a reversible fashion. Preliminary results showed that electron-deficient arenes such as chlorobenzene can also be used as the reaction partner.
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