Metal‐free, visible‐light‐induced site‐selective heteroarylation of remote C(sp3)−H bonds has been accomplished through the design of N‐alkoxyheteroarenium salts serving as both alkoxy radical precursors and heteroaryl sources. The transient alkoxy radical can be generated by the single‐electron reduction of an N‐alkoxypyridinium substrate by a photoexcited quinolinone catalyst. Subsequent radical translocation of the alkoxy radical forms a nucleophilic alkyl radical intermediate, which undergoes addition to the substrate to achieve remote C(sp3)−H heteroarylation. This cascade strategy provides a powerful platform for remote C(sp3)−H heteroarylation in a controllable and selective manner and is well suited for late‐stage functionalization of complex bioactive molecules.
By employing an N-heterocyclic carbene (NHC) catalyst, we developed a versatile catalytic system that enables deaminative cross-coupling reactions of aldehydes with redox-active pyridinium salts.
A strategy for visible-light-induced
site-selective C–H
acylation of pyridinium salts was developed by employing N-methoxy- or N-aminopyridinium salts, offering a
powerful synthetic tool for accessing highly valuable C2- and C4-acylated
pyridines. The methoxy or amidyl radicals photocatalytically generated
from the pyridinium salts can undergo hydrogen atom abstraction from
readily available aldehydes to form acyl radicals, which can engage
in addition to pyridinium substrates. Remarkably, the use of N-methoxypyridinium salts preferentially gives the C2-acylated
pyridines, and the site selectivity can be switched from C2 to C4
by using N-aminopyridinium salts. The utility of
this transformation was further demonstrated by the late-stage functionalization
of complex biorelevant molecules and by application of acyl radicals
to photocatalytic radical cascades.
Metal-free,v isible-light-induced site-selective heteroarylation of remote C(sp 3 ) À Hb onds has been accomplished through the design of N-alkoxyheteroarenium salts serving as both alkoxy radical precursors and heteroaryl sources.T he transient alkoxy radical can be generated by the single-electron reduction of an N-alkoxypyridinium substrate by ap hotoexcited quinolinone catalyst. Subsequent radical translocation of the alkoxy radical forms an ucleophilic alkylr adical intermediate,w hich undergoes addition to the substrate to achieve remote C(sp 3 ) À Hh eteroarylation. This cascade strategy provides ap owerful platform for remote C(sp 3 ) À H heteroarylation in ac ontrollable and selective manner and is well suited for late-stage functionalization of complex bioactive molecules.
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