Stereochemistry of organophosphorus cylic compounds—XV: Synthesis of tetramethylammonium salt of 2-oxo-2-thio-1,3,2,-oxazaphosphorinan and its crystal and molecular structures

2-Hydroxy-1,3,-2-oxazaphosphorinan-2-thione (5) was prepared by alkaline hydrolysis of 2-chloro-1,3,2-oxazaphosphorinan-2- thione (6). Treatment of the latter with sodium methoxide afforded the 2-methoxy-derivative 7 from which the tetramethylammonium salt of the thioacid 5 was obtained by the action of trimethylamine. The structure of this salt has been determined by the direct method and refined by least-squares to R = 0.0734, a = 12.303(4), b = 9.041(3), c = 10.419(2) Å, space group P2₁2₁2₁. The 2-oxo-2-thio-1,3,2-oxazaphosphorinanyl anion is in the chair form with the exocylic S and O atoms in an axial and equatorial position, respectively. An intermolecular H-bond between S and the endo-cyclic N atom is present in the solid-state structure.