An Iron‐Catalyzed Route to Dewar 1, 3, 5‐Triphosphabenzene and Subsequent Reactivity. Issue 37 (9th August 2022) - Barrett, Adam N.
Abstract: 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. Abstract : A mild, scalable iron‐catalyzed route to a Dewar phosphabenzene is presented. This species isomerizes in the presence of base to form the 1, 3, 5‐phosphabenzene, which then spontaneously rearranges to a novel triphospha(tricyclo) species. Onward coordination chemistry of all three phosphines is explored along with an extensive study into the reactivity of the Dewar phosphabenzene.