Synthesis and conformational analysis of 2-arylseleno-1,3-dithianes. Crystal and molecular structure of 2-(4-methoxyphenylseleno)- and 2-(4-trifluoromethylphenylseleno)-1,3-dithiane

Abstract

The synthesis of 2-(4-methoxyphenylseleno)-1,3-dithiane 3 and 2-(4-trifluoromethylphenylseleno)-1,3-dithiane 5 from 2-chloro-1,3-dithiane 1 and the corresponding sodium arylselenolates is described. Nuclear magnetic resonance spectroscopic investigation of the products indicates that the compounds exist predominantly in a conformation in which the arylseleno moiety adopts an axial orientation. X-ray crystallographic investigation indicates that the 1,3-dithiane ring exists in the chair conformation with the arylseleno moiety in the axial orientation. Compound 3 is orthorhombic, space group P212121 with a = 5.449(2) Å, b = 9.217(2) Å, c = 24.860(3) Å, V = 1248.5 Å3, Z = 4. The structure was refined to R = 0.038 for 689 reflections with I > 2.3σ(I). Compound 5 is monoclinic, space group C2/c, with a = 28.628(7) Å, b = 5.246(2) Å, c = 21.342(5) Å, β = 121.12(1)°, V = 2743.8 Å3, Z = 8. Its structure refined to R = 0.064 for 966 reflections with I > 2.3σ(I).