Base-mediated addition of acridones to allenylphosphonates/allenylphosphine oxides (OCH₂CMe₂CH₂O)P(O)CH=C=CR¹R² {R¹ = R² = Me (1), R¹ = R² = [−CH₂−]₅ (2)}, Ph₂P(O)C(H)=C=CR¹R² {R¹ = R² = Me (3), R¹ = R² = [−CH₂−]₅ (4)} and (EtO)₂P(O)C(H)=C=CMe₂ (5) in DMF results in the regiospecific formation of phosphono-acridones and acridonylphosphine oxides. The acridone addition products were also obtained in the reaction of allenes 1 and 2 with 9-chloroacridine under [Pd]-catalysed conditions, along with (unexpected) 𝛼-acridinyl substituted allenes. In contrast, 9-benzyl-6-chloro-purine reacted with 1 affording a 𝛽-substituted purinone phosphonate. Allenes 1-2 did not react with acridones in the absence of base (CsF), but in the presence of Pd(OAc)₂/DMF (or DMA)/pivalic acid rearranged to give 1,3-butadienes probably via [Pd]-allyl complexes. The phosphono-acridones were amenable to Horner-Wadsworth-Emmons (HWE) reaction and led to 𝑁-substituted acridones. Key products have been characterized by single-crystal X-ray crystallography.