NMR and symmetry in bisphosphonates R¹R²N-CH[P(O)(OMe)₂]₂

GRAPHICAL ABSTRACT

ABSTRACT

(Amino-methylene)bisphosphonates R¹R²N-CH[P(O)(OMe)₂]₂ bearing achiral and chiral substituents (R¹ = Ph, R² = H, Me; and R¹ = PhCH(Me), R² = Me, Bn) were synthesized and characterized in CDCl₃ by ¹H, ¹H{³¹P}, ¹³C{¹H}, ³¹P{¹H}, and ³¹P NMR spectra. [P(O)(OMe)₂]₂ fragments from achiral compounds give rise to complex ¹H NMR spectra characteristic for the [A₃M₃X]₂ ¹H NMR spectra while chiral compounds yield A₃G₃M₃T₃XY type spectra. Aspects of molecular symmetry governing the multiplet patterns are discussed and precise spectral parameters are calculated by line-shape iterations.

KEYWORDS:

• (Amino-methylene)bisphosphonates
• methyl esters
• multinuclear NMR
• spin systems
• line-shape iterations
• grid net search

Acknowledgments

Thanks are due to Ms. Beate Rau for dedicated NMR measurements using the 500 and 600 MHz spectrometers at Düsseldorf. Compounds 5 and 6 were provided by Dr. W. Plöger, formerly Henkel KGaA, Düsseldorf, Germany. Special thanks are due to Prof. R. K. Harris, formerly UEA Norwich, GB, for supporting our early attempts to understand the [A₃M₃X]₂ spectra.

Funding

Thanks are due to the Hungarian Scientific Research Fund: Grant number: Erika Bálint, (PD111895).