Synthesis of N,P‐Disecondary o‐Arylphosphanylanilines via o‐R¹NHC₆H₄P(R)O₂Et Precursors and Preliminary Study of Cyclocondensations with (EtO)₃CH/NH₄PF₆

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N ‐Secondary o ‐aminophenylarylphosphinates were prepared by Pd‐catalyzed cross coupling of aryl‐P(OEt) 2 with the corresponding o ‐bromoanilines and reduced with LiAlH 4 to o ‐phosphanylanilines. For the N ‐mesityl compounds a two‐step reduction was necessary because of competing P–N condensation reactions. Preliminary studies of cyclocondensations of o ‐(RPH)C 6 H 4 NHR 1 with (EtO) 3 CH/NH 4 PF 6 showed that, in contrast to benzimidazolium salts, accessible in this way from disecondary o ‐phenylenediamines, the homologous 1,3‐benzazaphospholium salts are highly reactive and undergo instantaneous oxidative addition of EtOH, liberated in the condensation. The resulting 3‐ethoxy‐benzazaphospholinium salts, which for R = Ph, R 1 = Np are relatively stable and were detected by NMR and HRMS, decompose to yield P‐oxo‐1,3‐benzazaphospholine · x HPF 6 salts, and for R 1 = Me additionally the rearranged N ‐ethyl‐P‐oxo‐benzazaphospholinium salt. Detection of triethylphosphate indicates partial acid‐catalyzed conversion of PF 6 – with EtOH. Alternative cyclocondensation of o ‐(MesPH)C 6 H 4 NHNp with excess Me 2 NCH(OMe) 2 in the presence of HCl/Et 2 O led to the 2‐methoxy‐, or after removal of MeOH under vacuum to the corresponding 2‐dimethylamino‐1,3‐benzazaphospholine. The structure elucidation of the new compounds is based on multinuclear NMR data and confirmed for an o ‐anilinophenylphosphinate by crystal structure analysis.