Abstract The title compounds 11 were obtained from δ-diketo-dipinacolyl phosphonium cations 8 by action of AcONH4/AcOH. These cations were prepared according to three different methods A, B and C. Method B allows a direct synthesis of cation 8 from a pinacolyl phosphine 6 and bromopinacolin 2. Methods A and C proceed by hydrolysis of the corresponding oxygen heterocycles 7 in acidic conditions, which were obtained by ...