Pd-Catalyzed C-H Activation Route to Dibenzophosphole Oxides

Significance

Reported is the synthesis of dibenzophosphole oxides via Pd-catalyzed dehydrogenative cyclization of biaryl secondary hydrophosphine oxides. These starting materials can be conveniently synthesized from bromo-biaryls by sequential formation of the Grignard reagents followed by reaction with dichlorophosphine. The yields are low when the phosphine contains a bulky group such as tert-butyl. The Pd-catalyzed annulation proceeds in good yields, and the substrate scope was reasonably well studied. The reaction does not proceed when R^² = 2-vinylphenyl due to polymerization of the substrate.