Benzylic C(sp3)–H Phosphonylation via Dual Photo and Copper Catalysis

Alkyl phosphonates are important motifs in medicinal chemistry, yet their efficient synthesis by direct C(sp3)–H functionalization remains a challenge. Here, we report straightforward access to benzylic phosphonates by direct C(sp3)–H functionalization in a cross‐dehydrogenative‐coupling reaction between non‐specialized alkylarenes and unfunctionalized phosphites. Notably, the C–H substrates are used as the limiting reagents. The scope of benzylic C–H substrates is broad, and the mild reaction conditions allow for good functional group tolerance. Mechanistic studies indicate that the reaction proceeds via a radical pathway rather than the cationic pathway followed for specialized benzylic C–H substrates in previous methods.