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Synthesis of N,P ‐Disecondary o ‐Arylphosphanylanilines via o ‐R 1 NHC 6 H 4 P(R)O 2 Et Precursors and Preliminary Study of Cyclocondensations with (EtO) 3 CH/NH 4 PF 6
Author(s) -
Aluri Bhaskar R.,
Ghalib Mohammed,
Jones Peter G.,
Frauendorf Holm,
Heinicke Joachim W.
Publication year - 2020
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201901069
Subject(s) - chemistry , medicinal chemistry , yield (engineering) , aryl , catalysis , crystal structure , salt (chemistry) , stereochemistry , crystallography , organic chemistry , alkyl , materials science , metallurgy
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.