A New Class of Chiral Phosphazene Bases: Synthesis and Characterization

Abstract

Abstract Chiral examples of phosphazene bases 2a – c were synthesized by treatment of ( S )‐2‐(dialkylaminomethyl)pyrrolidine 1a – c , derived from 5‐oxo‐( S )‐proline, with phosphorus pentachloride and subsequent addition of gaseous ammonia. The phosphazenes 2a – c were isolated as HBF 4 salts in high yields and fully characterized by 1 H, 13 C and 31 P NMR spectroscopy, various 1D and 2D NMR experiments and mass spectrometry (EI). The molecular structure and the absolute configuration of the salts 2a – c· HBF 4 were determined by X‐ray analysis. DFT calculations indicate that 2a is more basic than the Schwesinger base P 1 by approximately nine p K a units. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)