In recent years, there has been great development of methodologies for direct activation of carbon-hydrogen (C-H) bonds ubiquitous in organic molecules. In particular, catalytic sp3C-H bond functionalization is an ideal transformation which satisfies the atom and step economy. However, sp3C-H bonds are usually extremely stable bonds, and their catalytic conversion often requires harsh reaction conditions. Radical catalysis, on the other hand, is an attractive approach because of its ability to abstract the sp3C-H bond and proceed under mild conditions. However, the reactivity of the carbon radical species is usually difficult to control and subsequent conversion is limited. As a possible strategy to solve this problem, I planned a multiple catalyst system based on photoredox catalyst, hydrogen atom transfer (HAT) catalyst and transition metal catalyst (Scheme 1). This system can catalytically generate organometallic species directly from sp3C-H bonds under very mild conditions and can be applied to a variety of transition metal-catalyzed reactions. In this time, I will discuss our recent progress.
 Fuse, H.; Irie, Y.; Fuki, M.; Kobori, Y.; Kato, K.; Yamakata, A.; Higashi, M.; Mitsunuma, H.; Kanai, M. J. Am. Chem. Soc. 2022, 144, 6566.  Tanabe, S.; Mitsunuma, H.; Kanai, M. J. Am. Chem. Soc. 2020, 142, 12374.  Fuse, H.; Mitsunuma, H.; Kanai, M. J. Am. Chem. Soc. 2020, 142, 4493.  Fuse, H.; Kojima, M.; Mitsunuma, H.; Kanai, M. Org. Lett. 2018, 20, 2042.