Synthesis and molecular structure of new phosphorous-crown compounds containing the thiophosphoryl group

Abstract

The synthesis and characterization of four phosphorus macrocycles (1–4) are reported. The X-ray crystal structures of compounds 1–4 and solvate 1·H₂O show the molecules in asymmetric conformations with at least one methyl group of the phenoxy substituents oriented toward the centre of the macrocyclic cavity. Variable-temperature ¹H NMR experiments show that in solution the molecules exist mainly as rapidly interconverting conformers. In the 18-membered ring 1, the dynamic process results in the enantiomerization of asymmetric conformers with a barrier of 8 kcal mol^–1.‡ The 21-membered ring 3 is more flexible and exists in several conformations.