Photocatalytic Arylation of P(4) and PH(3): Reaction Development Through Mechanistic Insight

Detailed (31)P{(1)H} NMR spectroscopic investigations provide deeper insight into the complex, multi‐step mechanisms involved in the recently reported photocatalytic arylation of white phosphorus (P(4)). Specifically, these studies have identified a number of previously unrecognized side products, which arise from an unexpected non‐innocent behavior of the commonly employed terminal reductant Et(3)N. The different rate of formation of these products explains discrepancies in the performance of the two most effective catalysts, [Ir(dtbbpy)(ppy)(2)][PF(6)] (dtbbpy=4,4′‐di‐tert‐butyl‐2,2′‐bipyridine) and 3DPAFIPN. Inspired by the observation of PH(3) as a minor intermediate, we have developed the first catalytic procedure for the arylation of this key industrial compound. Similar to P(4) arylation, this method affords valuable triarylphosphines or tetraarylphosphonium salts depending on the steric profile of the aryl substituents.