Ferrocenium salt induced ring expansion of a 2H-azaphosphirene complex: Synthesis of the first Δ3-1,4,2-oxazaphospholene complexes †

Abstract

Regioselective ring expansion of the 2H-azaphosphirene tungsten complex 1 in CH₂Cl₂ is performed using sub-stoichiometric amounts of ferrocenium hexafluorophosphate and benzalaldehyde or cyclohexanone, thus yielding Δ³-1,4,2-oxazaphospholene complexes 2a,c; the molecular structure of complex 2c was established by a single crystal X-ray diffraction study.