Visible-Light-Induced Direct C(sp³)–H Phosphorylation through Radical Cross-Coupling by Polyoxomolybdate Photocatalyst

Photocatalytic C(sp3)–H phosphorylation was achieved using an easy-available polyoxomolybdate ([N(C4H9)4]2[Mo6O19]) as the photocatalyst. In the developed visible-light-induced C(sp3)–P bonds construction methodology, xanthenes/9,10-dihydroacridines/4-benzyl-3,4-dihydroquinoxalin-2(1H)-one could serve as useful C(sp3)–H donors that could smoothly couple with P(O)–H compounds, delivering the target products with wide substrate scope and good functional group compatibility. Moreover, this Lindquist-type polyoxomolybdate possessed excellent stability and reusability as well as satisfying photoreactivity under sunlight irradiation. The mechanism researches revealed that C(sp3)–P bonds were most probably constructed through the cross-coupling of C(sp3) radicals and P-centered radicals, rather than the cationic pathway and radical trapping pathway reported in the previous methods. This organic ligand- and noble metal-free photosensitizer represents an alternative photocatalyst to realize dehydrogenative coupling reactions under metal-, additive-, base-, and external oxidant-free conditions.