Stereoselective synthesis of trans N/O dispirocyclic cyclotriphosphazenes based on the steric demands of the constrained 2-pyridyl group

• Published in: Inorganic chemistry communications Vol. 35; pp. 330 - 332
• Main Authors: Kajiyama, Kazumasa, Suzuki, Masataka, Kojima, Masanori, Setone, Yuki
• Format: Journal Article
• Language: English
• Published: AMSTERDAM Elsevier B.V 01.09.2013; Elsevier
• Subjects: 2-(2-Pyridylamino)phenol; Chemistry; Chemistry, Inorganic & Nuclear; Physical Sciences; Science & Technology; Stereoselective synthesis; Trans dispirocyclic cyclotriphosphazene; X-ray crystal structural analysis; 2-(2-Pyridylamino)phenol; X-ray crystal structural analysis; Trans dispirocyclic cyclotriphosphazene; Stereoselective synthesis; PHOSPHAZENES; LIGANDS; 2-(2-Pyridylamino)pheno
• ISSN: 1387-7003; 1879-0259
• DOI: 10.1016/j.inoche.2013.07.016

Monospiro- and dispirocyclic cyclotriphosphazenes, 2a and 2b, were synthesized by the reaction of hexachlorocyclotriphosphazene, N3P3Cl6 (1), with 2-(2-pyridylamino)phenol in the presence of base. The reactions of phosphazenes 2a and 2b with sodium (4-methyl-2-pyridyl)oxide afforded tetrakis- and bis(4-methyl-2-pyridyloxy)cyclotriphosphazenes, 3a and 3b, respectively. 31P NMR spectroscopy of 2b and 3b using d-camphorsulfonic acid as a chiral solvating agent indicated that they were racemates of the trans isomers. The trans configuration of trans-3b could also be elucidated by X-ray crystal structural analysis, which suggested that the steric demand of the 2-pyridyl group was responsible for the stereoselective formation of trans-2b. The steric demand of the 2-pyridyl group was supported by the reaction of N3P3Cl6 (1) with N,N′-bis(2-pyridyl)benzene-1,2-diamine, which only gave monospirocyclic cyclotriphosphazene 4a. The highly distereoselective formation of trans dispirocyclic cyclotriphosphazene trans-2b could be achieved by the reaction of hexachlorocyclotriphosphazene 1 with 2-(2-pyridylamino)phenol. The trans configuration of the alkoxy derivative trans-3b was elucidated by X-ray crystal structural analysis. [Display omitted] •The reaction of N3P3Cl6 with 2-(2-pyridylamino)phenol is investigated.•Dispirocyclic cyclotriphosphazene is yielded with high trans-selectivity.•The racemic identity of trans phosphazene is verified by 31P NMR analysis with CSA.•The configuration of trans phosphazene is elucidated by X-ray structural analysis.