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.
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