The Effect of Trifluoroethoxy Groups on the Structures of Eight-Membered Ring-Containing Cyclic Phosphites¹

Abstract

New phosphites 1–4 were synthesized from phosphorus trichloride and an appropriate diphenol followed by the addition of trifluoroethanol in the presence of triethylamine. These phosphites are to serve as precursors in the syntheses of biorelated hypervalent phosphoranes. ¹H, ¹⁹F, and ³¹P NMR spectra were recorded. X-ray analysis of 3 and 4 revealed that the sulfur-containing eight-membered ring was in a syn conformation that a allowed a sulfur donor interaction to the phosphorus atom, whereas for phosphite 2, the eight membered sulfonyl containing ring was in an anti conformation that did not allow a donor interaction to phosphorus from the oxygen atom of the sulfonyl group. Structural comparisons are made with related cyclic phosphites and phosphates having donor atoms in eight-membered rings.

Keywords:

• Cyclic phosphites
• phosphorus-sulfur donor interactions
• trifluoroethoxy groups
• X-ray crystallography

Acknowledgments

The research presented here was supported by the donors of the Petroleum Research Fund, administered by the American Chemical Society, and is gratefully acknowledged. We thank the X-Ray Structural Characterization Laboratory at the Chemistry Department supported by University of Massachusetts and National Science Foundation (Grant CHE-9974648).

Notes

^a R = Σ‖F_o|-|F_c‖/Σ|Fo|

^b R_w(F_o ²) = {Σw(F_o ² − F_c ²)²/ΣwF_o ⁴}^½.