Photoredox catalysis has re-emerged as a powerful platform for synthesizing high-value molecules academically and industrially. This lecture discusses photochemical systems that harness, transduce, regulate, or transfer visible-light photon energy to drive challenging transformations, enabling activation of inert bonds—including simultaneous activation of two bonds—and new bond-construction strategies such as heteroarene insertion into carbon–heteroatom bonds. Visible-light-driven nickel photoredox catalysis is presented for general C(sp²)–(hetero)atom cross-coupling: the adaptive AD-HoC platform enables systematic categorization and predictable coupling of diverse nucleophiles, demonstrated across nine bond-forming reactions (C(sp²)–S, Se, N, P, B, O, C(sp³/sp²/sp), Si, Cl) spanning hundreds of examples, with reaction centre and conditions adaptable via nucleophile choice and, if needed, an inexpensive amine base. Finally, a complementary two-electron regime enables alkene dicarbofunctionalization with organic halides and CO₂, yielding carboxylic acids via two C–C bond-forming events: combining halogen-atom transfer (XAT) and single-electron transfer (SET) activates aryl/alkyl halides beyond conventional reduction limits, with XAT generating carbon radicals and SET promoting carbanion formation and CO₂ incorporation, giving carboxylated products in yields up to 94% across fifty-plus examples.
