The reaction of dihydroxyacetone with ethanedithiol. Synthesis and x‐ray crystal structure of 1,4,7,10‐tetrathiaspiro[5.5]undecane

Reaction of dihydroxyacetone with an excess of ethanedithiol in the presence of 10 M hydrochloric acid gives 2,2‐di(hydroxymethyl)‐1,3‐dithiacyclopentane ( 1 ) in low yield. When boron trifluoride etherate is used instead of hydrochloric acid, the same reactants give 1,4,7,10‐tetrathiaspiro[5. 5]undecane ( 3 ). The structure of the latter was established by X ‐ray crystallography. The crystals are monoclinic, space group P2,/n, with a = 6.31(1), b = 21.57(2), c = 7.61(1)Å, β = 102.2(1)° and Z = 4, R = 0.038 for 2289 reflections. The two 1,4‐dithiane rings in 3 are significantly more puckered than normal cyclohexane rings. The uv spectrum of 3 is consistent with values reported for other sulphides and with the X‐ray structure.