Advances in N-centered intermediates by energy transfer photocatalysis

Abstract

Energy transfer (EnT) processes are highly selective and complementary to photoredox catalysis; molecules with redox potentials that are incompatible with that of the excited photocatalyst (PC) can be activated via the EnT process by the high excited energy of the PC. EnT photocatalysis has selectively generated key nitrogen reactive intermediates such as iminyl radicals and nitrenes from a variety of N-containing molecules, and mechanistic studies have guided the process. EnT strategies are maintained by excellent atom economy by utilizing both of the radical fragments generated via homolytic bond cleavage in the absence of sacrificial additives. The synthetic outlook for N-radical chemistry has been expanded to cascade photocatalysis by combining EnT and SET mechanistic cycles. Advances in visible-light-mediated energy transfer (EnT) catalysis have created a unique strategy for small-molecule activation and new chemical bond formation in organic synthesis. In particular, open-shell nitrogen reactive intermediates have emerged as versatile synthons for various cross-coupling reactions and the construction of N-heterocycles. Visible-light-induced EnT catalysis produced N-radicals and nitrenes based on their parent chemical structure disconnections. In this review, we highlight the key contributions in the field with an emphasis on the studies that have generated and utilized N-centered intermediates, and provide mechanistic insights on these photocatalytic processes. Advances in visible-light-mediated energy transfer (EnT) catalysis have created a unique strategy for small-molecule activation and new chemical bond formation in organic synthesis. In particular, open-shell nitrogen reactive intermediates have emerged as versatile synthons for various cross-coupling reactions and the construction of N-heterocycles. Visible-light-induced EnT catalysis produced N-radicals and nitrenes based on their parent chemical structure disconnections. In this review, we highlight the key contributions in the field with an emphasis on the studies that have generated and utilized N-centered intermediates, and provide mechanistic insights on these photocatalytic processes. the photophysical process in which an excited state of a donor molecule (PC) is disabled to a lower-lying state by the transfer of energy to an acceptor molecule (substrate), which is raised to a higher-energy state. the bonding electron pair is fragmented equally between the radicals during the bond-breaking process. a concerted movement of a proton and an electron (i.e., hydrogen radical) in a single kinetic step from one group to another. a dynamic process involving spin-orbit coupling between electronic states belonging to different electron spin multiplicities. radiation-induced process in which no energy is exchanged with the radiation field. a kinetic phenomenon that explains the selective cross-coupling between two different radicals that are generated at an equal rate and have different lifetimes. The persistent (long lived) radicals do not self-terminate and react only in cross-couplings. an event where an electron moves from an organic or inorganic donor molecule to an acceptor molecule, resulting in a change in the oxidation state of the reactant and product. a chemical compound that is used to react with unstable radicals to produce stable trapped product.