The alkylation and heteroarylation of unactivated tertiary,
secondary,
and primary C(sp3)–H bonds was achieved by employing
an acridinium photoredox catalyst along with readily available pyridine N-oxides as hydrogen atom transfer (HAT) precursors under
visible light. Oxygen-centered radicals, generated by single-electron
oxidation of the N-oxides, are the proposed key intermediates
whose reactivity can be easily modified by structural adjustments.
A broad range of aliphatic C–H substrates with electron-donating
or -withdrawing groups as well as various olefinic radical acceptors
and heteroarenes were well tolerated.
Direct Functionalization of alkynes under oxidative is challenging, as alkynes are usually recalcitrant towards typical oxidants. Herein, we communicate a strategy for the divergent functionalization of alkynes with photoexcited acridinium organic dyes, presumably via the formation of vinyl cation radicals as key intermediates. Based on the nature of the nucleophiles, different types of difunctionalized products were obtained in moderate to good yields. Addition of lithium Lewis acids resulted in a surprising reversal of diastereocontrol.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.