An Iron‐Catalyzed Route to Dewar 1,3,5‐Triphosphabenzene and Subsequent Reactivity

The application of an alkyne cyclotrimerization regime with an [Fe(salen)](2)‐μ‐oxo (1) catalyst to triphenylmethylphosphaalkyne (2) yields gram‐scale quantities of 2,4,6‐tris(triphenylmethyl)‐Dewar‐1,3,5‐triphosphabenzene (3). Bulky lithium salt LiHMDS facilitates a rearrangement of 3 to the 1,3,5‐triphosphabenzene valence isomer (3′), which subsequently undergoes an intriguing phosphorus migration reaction to form the ring‐contracted species (3′′). Density functional theory calculations provide a plausible mechanism for this rearrangement. Given the stability of 3, a diverse array of unprecedented transformations was investigated. We report novel crystallographically characterized products of successful nucleophilic/electrophilic addition and protonation/oxidation reactions.