Reversible Formation and Cleavage of C─C and C─Br Bonds Enabled by an Organic Photocatalyst

Reversible formation and cleavage of covalent bonds hold promise for organic synthesis, polymeric materials, dynamic covalent networks, and drug delivery. However, such reversibility has predominantly relied on labile covalent bonds, such as ester, thioester, amide, and disulfide bonds. Herein, we report the reversible formation and cleavage of conventionally irreversible C─C and C─Br bonds enabled by an organic photocatalyst. Using the single photocatalyst isosulfonyltruxene ( ITSO 2 ), we accomplish reductive pinacol coupling of ketones to vicinal diols and the reverse oxidative cleavage. Moreover, this system also facilitates oxidative bromination of alkenes to vicinal dibromides and the reverse reductive debromination. Notably, this platform proves applicable to the synthesis and degradation of polymeric diols, as well as reversible modification of rubber. Mechanistic studies reveal that ITSO 2 inherently exhibits potent oxidizing capacity to facilitate oxidative C─C bond cleavage and C─Br bond formation, which can be converted into highly reducing photoactive species under net‐reductive photochemical conditions, thereby enabling reductive C─C bond formation and C─Br bond cleavage.