1,2-dithietanes, 4-membered rings where the two sulfur atoms are adjacent, are very rare. The first stable 1,2-dithietane to be reported was the dithiatopazine, formed by intramolecular photodimerization of a dithiocarbonyl compound.[3] 1,2-Dithietanes are to be distinguished from 1,2-
dithietes, containing two adjacent sulfur atoms and two
sp2-hybridized carbon centers.
Structure of trans-3,4-diethyl-1,2-dithietane 1,1-dioxide, the dimer of the onion lachrymatory agent
1,3-Dithietanes
In
1,3-dithietanes, the
sulfur atoms are non-adjacent.[5] 1,3-Dithietane itself, a colorless, easily sublimed, crystalline, unpleasant-smelling solid with
melting point 105-106 °C, was first prepared in 1976 by reaction of bis(chloromethyl) sulfoxide with
sodium sulfide followed by THF-
borane reduction of the first formed 1,3-dithietane 1-oxide, as shown in the scheme below.[6][7] Carbon-substituted 1,3-dithietanes are well known, with the first examples being described as early as 1872. Examples include 2,2,4,4-tetrachloro-1,3-dithietane, the
photochemically-formed dimer of
thiophosgene, and tetrakis(trifluoromethyl)-1,3-dithietane, [(CF3)2CS]2.[8]
Synthesis of 1,3-dithietane
Oxidized forms of 1,3-dithietane are well known, although they are often not prepared from the dithietane. Examples include the so-called zwiebelanes (2,3-dimethyl-5,6-dithiabicyclo[2.1.1]hexane S-oxides) from onion volatiles[9] and 1,3-dithietane 1,1,3,3-tetraoxide, the so-called
sulfene dimer.[10]
Left:
thiophosgene dimer, 2,2,4,4-tetrachloro-1,3-dithietane; center: a zwiebelane, found in onion volatiles; right: sulfene dimer
References
^Drabowicz, J; Lewkowski, J; Kudelska, W; Zając, A (2008). "Four-membered Rings with Two Sulfur Atoms". Comprehensive Heterocyclic Chemistry III. 2 (18): 811–852.
doi:
10.1016/B978-008044992-0.00218-2.
^Nicolaou, KC; Hwang, CK; Duggan, ME; Carroll, PJ (1987). "Dithiatopazine. The first stable 1,2-dithietane". J. Am. Chem. Soc. 109 (12): 3801–3802.
doi:
10.1021/ja00246a059.
^Block, E; Bazzi, AA; Revelle, LK (1980). "The chemistry of sulfines. 6. Dimer of the onion lachrymatory factor: the first stable 1,2-dithietane derivative". J. Am. Chem. Soc. 102 (7): 2490–2491.
doi:
10.1021/ja00527a074.