Synthesis of 1,2-dihydro-1,3-diaza-2λ5,4λ5-2,4-diphosphorine 2-oxides

The reaction of lithium (N-diphenylphosphoryl)phosphazenes with nitriles afforded 1,2-dihydro-1,3-diaza-2λ5,4λ5-2,4-diphosphorine 2-oxides through a C-regioselective addition to the cyano linkage followed by in situ cyclocondensation. The new heterocycles were designed to mimic thymine and are promising chemotherapeutic anticancer agents. As an exception, for p-nitrobenzonitrile a SNAr reaction was exclusively observed with the nucleophile entering in the ortho position of the nitro substituent in a process directed by the strong electron withdrawing effect of the NO2 group.