The crystal structures of four alkyl 3-oxo-2-(triphenylphosphoranylidene)butyrates, where the alkyl group is methyl (C₂₃H₂₁O₃P·0.5C₆H₆), (II), ethyl (C₂₄H₂₃O₃P), (III), isopropyl (C₂₅H₂₅O₃P), (IV), or tert-butyl (C₂₆H₂₇O₃P), (V), show all of them to have the same conformation. They present a tetrahedral P atom and an sp² ylidic C atom, with the carbonyl groups adopting anti conformations with respect to the keto groups located close to the P atom. P–C–C–O torsion angles, bond lengths and angles indicate an effective electronic delocalization toward the keto groups. In each case, one H atom of the alkoxy group is close to one of the phenyl rings. These preferred conformations are evaluated as the result of attractive and repulsive intramolecular interactions.