Although Iron catalysts are expected to be useful for redox reactions because they possess rich multivalent states and are easily accessible, selective studies on these characteristic features of Iron have hardly progressed. Iron(III)-polypyridyl complex and its derivatives show the sufficient oxidizing potential to act as an one-electron oxidant to produce the radical cations of olefins, therefore it can promote the efficient radical cation cycloaddition of electron-rich dienophiles. It is well-known that photocatalysts or organic catalysts conduct the electronically mismatched cycloaddition such as [2+2] or [2+4] cycloaddition (Diels-Alder reaction). Recent study is going along with Ru(II) or Cr(III)<sup> </sup>polypyridyl complexes as a photocatalyst and demonstrates that chain propagation steps dominate product formation in polar radical cycloaddition mechanism compared to initiation step. Based on current research, we performed radial cation catalyzed [2+2] and [4+2] cycloaddition using Fe(III) polypyridyl complexes as effective radical cation generator. Fe(III) complexes were capable of single electron oxidation of some kinds of anethole derivatives and oxidized anethole derivatives reacted with styrene or isoprene derivatives to produce cycloadduct radical cation. This radical cation could complete the reaction by chain propagation and consequently trisubstituted cyclobutane or cyclohexene derivatives could be synthesized. Although they cannot carry out whole catalytic cycle, it can be a facile route to replace rare metals with the sustainable, green and inexpensive iron to make an effective radical cation cycloaddition reaction.

Electronically mismatched cycloaddition reactions via single-electron-transfer of iron(III)-polypyridyl complex

256th National Meeting (2018)

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