Visible-light-induced site-selective heteroarylation of remote C(sp3)–H bonds has been accomplished through the design of N-alkoxyheteroarenium salts as both alkoxy radical sources and heteroaryl group sources. The alkoxy radical can be generated through the single electron reduction of N-alkoxypyridinium derivatives by a photoexcited quinolinone catalyst (Q1*). Subsequent radical translocation (1,5-HAT) of the O-centered radical forms a C-centered radical intermediate, which undergoes addition to the pyridinium substrate to achieve remote C(sp3)–H heteroarylation. This strategy provides a powerful platform for remote C(sp3)–H heteroarylation in a controllable and selective manner for the synthesis of a broad range of 4-heteroaryl alcohol products which have quaternary, tertiary, and secondary carbon centers.
Also we developed a new approach to site-divergent pyridine functionalization that offers considerable advantages in both simplicity and efficiency. The site-selectivity can be switched from C2 to C4 by changing the radical coupling sources. Under standard reaction conditions, phosphinoyl radicals give access to C4 products, while carbamoyl radicals selectively give C2 products. These current methods are well suited for late-stage functionalization of complex bioactive molecules.
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