Synthesis of Novel 8‐cyclo‐1,5,3,7‐Diazadiphosphocine Derivatives Via [4 + 2] Cycloaddition

Abstract

As part of our research program into pharmacologically valuable compounds and chelating agents for transition metal ions, novel 8‐cyclo‐1,5,3,7‐diazadiphosphocines (5–16) were successfully synthesized in good yields via [4 + 2] cycloaddition reaction between 8‐cyclo‐1,5,3,7‐diazadiphosphocines (4a‐c) with dienophiles (dimethyl acetylenedicarboxylate [DMAD], diethyl acetylenedicarboxylate [DEAD], diethyl diazene‐1,2‐dicarboxylate [DEDAD], and diisopropyl diazene‐1,2‐dicarboxylate [DIPDAD]). The core precursor scaffolds (4a‐c) were prepared via a one‐pot reaction between heteroaromatic amine analogs (1a‐c), paraformaldehyde and hypophosphorous acid in the presence of 6 M HCl. The biological activity of all synthesized 8‐cyclo‐1,5,3,7‐diazadiphosphocines (4a‐c, and 5–16) was evaluated against several cancer cell lines.