Cyclotriphosphazenes having stereogenic phosphorus atoms: Synthesis, characterization and their stereogenic properties

Abstract

Cyclotriphosphazene derivatives (4–6) with stereogenic phosphorus atoms were synthesized to investigate their stereogenic properties. The unsymmetrical reagents 3-amino-1-propanol and N-methyl-1,3-propanediamine were used to provide two equivalent stereogenic centers on phosphorus atoms and an unsymmetrical substituted phosphorus atom, respectively. The compounds N3P3[O(CH2)3NH]2[O(CH2)2NMe] (4–6) (diastereoisomers) were separated by column chromatography on silica gel and analyzed by elemental analysis, mass spectrometry, and 31P and 1H NMR spectroscopies. In addition, the structure of compound 5 was determined by X-ray crystallography. All the compounds (4–6) were analyzed by the changes in the 31P NMR spectra on addition of the chiral solvating agent (CSA), (R)-(+)-2,2,2-trifluoro-1-(9′-anthryl)ethanol to investigate their stereogenic properties. The results support that compounds 4–6 are three different diastereoisomers with chiral centres, and whilst compound 4 is racemic, compounds 5 and 6 are meso.