Synthesis of 1,2,4-diazaphospholes via base-promoted cyclization reaction of hydrazonoyl chlorides and [Bu 4 N][P(SiCl 3 ) 2 ].

Aromatic 1,2,4-diazaphospholes featuring distinct hybrid-mode nitrogen atoms (N(λ 3 σ 2 ), N(λ 3 σ 3 )) and low-valent phosphorus atoms (λ 3 σ 2 ) exhibited the characteristic of serving as unique hybrid ligands. This study presented a one-pot reaction involving the base-promoted stepwise cyclization of hydrazonoyl chlorides and [Bu 4 N][P(SiCl 3 ) 2 ] to yield 1,2,4-diazaphospholes, providing an effective method for synthesizing such compounds.