CONFORMATIONAL ANALYSIS OF DIALKYL (2,5-DIALKYL PYRROLIDIN-2-YL)PHOSPHONATES AND DIETHYL(2,5,5-TRIMETHYL PYRROLIDIN-2-YL)PHOSPHONATE BY X-RAY ANALYSIS, NMR AND FORCE FIELD CALCULATIONS

Abstract

Using force field calculations (MM2), ¹H, ¹³C NMR spectroscopy and X-ray diffraction, conformational studies were performed on four substituted (pyrrolidin-2-yl) phosphonates 1–4. According to force field calculations, one type of conformation (twist form around C⁴ and C⁵ atoms) was found to be strongly favoured for compounds 2–4 while for 1 an equilibrium between two envelope forms on the C⁴ atom was established. ¹H NMR parameters obtained from simulations of spectra with the LAOCOON program as well Karplus relationships were in good agreement with the calculated geometries.

Key Words:

• Dialkyl(pyrrolidin-2-yl)phosphonates
• conformational analysis
• NMR studies
• molecular mechanics
• X-ray diffraction