Ferrocenium salt induced ring expansion of a 2H-azaphosphirene complex: Synthesis of the first Delta(3)-1,4,2-oxazaphospholene complexes

Regioselective ring expansion of the 2H-azaphosphirene tungsten complex 1 i n CH2Cl2 is performed using sub-stoichiometric amounts of ferrocenium hexaf luorophosphate and benzalaldehyde or cyclohexanone, thus yielding Delta(3)- 1,4,2-oxazaphospholene complexes 2a,c; the molecular structure of complex 2 c was established by a single crystal X-ray diffraction study.