Visible-Light-Induced Direct C(sp<sup>3</sup>)–H Phosphorylation through Radical Cross-Coupling by Polyoxomolybdate Photocatalyst
Ye Li, Qiaoyu Gan, Xiaosong Wang, Xi Chen, Xinghua Zhang, Yingli Liu, Zeqi Jiang
Abstract
Photocatalytic C(sp 3 )–H phosphorylation was achieved using an easy-available polyoxomolybdate ([N(C 4 H 9 ) 4 ] 2 [Mo 6 O 19 ]) as the photocatalyst. In the developed visible-light-induced C(sp 3 )–P bonds construction methodology, xanthenes/9,10-dihydroacridines/4-benzyl-3,4-dihydroquinoxalin-2(1 H )-one could serve as useful C(sp 3 )–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(sp 3 )–P bonds were most probably constructed through the cross-coupling of C(sp 3 ) 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.