Cyclic phosphazene derivatives combined with two different forms of the phenol-pyrazole group: synthesis, spectroscopic and crystallographic characterization and stereochemical properties†

Nucleophilic substitution reactions of the phenol pyrazole group {2-(1H-pyrazol-3-yl)phenol} (2) containing N and O donor atoms with hexachlorocyclotriphosphazene (N₃P₃Cl₆) (1) were carried out, and the product variety was examined. As a result of the reaction carried out at a 1 : 1.2 mole ratio, a mono spiro product (3) and a mono spiro and mono N-substituted phenol pyrazole containing isomer mixture (4a and 4b) were obtained. For the reaction carried out at a mole ratio of 1 : 2.5, trans bis spiro (5), trans bis spiro and mono N-substituted phenol pyrazole compound (6), trans bis spiro and geminal bis N-substituted phenol pyrazole compound (7), and tris spiro cis–trans–trans (8a) and cis–cis–cis (8b) were obtained. Due to tautomerism in the pyrazole ring, while mono-spiro products are formed in the phenol pyrazole 5-yl tautimeric form, it has been determined that the pyrazole 3-yl tautomer is mono-functionally substituted at the N end of the cyclotriphosphazene ring, confirmed by single crystal X-ray diffraction technique. The isolated compounds (3–8) were characterized by elemental analysis, FT-IR, MALDI-TOF mass spectrometry, 1D (¹H, ³¹P) and 2D (¹³C APT-attached proton test, HETCOR-heteronuclear correlation) NMR spectroscopies. The crystal structures of 3 and 5–7 were illuminated by single crystal X-ray crystallography. Van der Waals interactions were identified as the primary intermolecular interactions in the crystal structures by Hirshfeld Surface (HS) analysis. At the same time, the chiral properties of all obtained compounds were evaluated, considering stereochemical terms.