Gold in Photocatalysis
S. Dix, M. N. Hopkinson – 2018
Dual catalytic systems combining gold and photocatalysis are capable of facilitating redox-neutral coupling reactions that are otherwise seldom observed using gold catalysts alone. The challenging oxidation of gold(I) to gold(III) in these processes is achieved through two single electron transfer steps involving photogenerated organic radicals derived most commonly from aryldiazonium salts. In addition to analogs of some classical cross-coupling processes that are tolerant of halogen functionalities, arylative 1,2-difunctionalization reactions of π-systems combining the traditional π-Lewis acidity of gold catalysts with coupling are accessible. These processes can be performed on alkene, allene and alkyne substrates with the unique mechanistic features of dual gold/photoredox catalysis allowing for improved selectivity for cross-coupling than is observed in alternative oxidative gold-catalyzed coupling methodologies.