Proton-coupled electron transfer (PCET) reactions, characterized by the simultaneous transfer of a proton and an electron, represent a distinctive class of non-classical redox processes. Recent studies have highlighted their potential as a viable strategy for activation in organic synthesis. In 2013, Knowles group demonstrated the use of Ru-based photocatalyst together with a phosphoric acid derivative to generate ketyl radicals from ketonebearing substrate (20.1) via PCET, resulting in a conjugate addition that yielded 78% of bicyclic product 20.3. In 2018, Collins and co-workers investigated a library of heteroleptic diamine diphosphine copper (I) complexes for a similar transformation (Figure ). Notably, [Cu(dq)(BINAP)]BF4 emerged as one of the most active complexes for the transformation achieving a 71% yield of the desired product 20.3 under blue light irradiation.