Catalyst-Free Phosphorylation of Acridine with Secondary Phosphine Chalcogenides: Nucleophilic Addition vs S N H Ar Reaction.

Acridine adds secondary phosphine chalcogenides HP(X)R2 (X = O, S, Se; R = Ar, ArAlk) under catalyst-free conditions at 70-75 °C (both in the presence and absence of the electron-deficient acetylenes) to give 9-chalcogenophosphoryl-9,10-dihydroacridines in 61-94% yields. This contrasts with pyridines, which under similar conditions undergo an SN H Ar reaction, wherein electron-deficient acetylenes play the role of oxidants. For acridine, the SN H Ar step has been accomplished by the oxidation of the intermediate 9-phosphoryl-9,10-dihydroacridines (X = O) with chloranil.